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SIX12 User's Manual
Version 8
BLISS-36 Compatible Version
TOPS10/TOPS20 Compatible Version
NOTE
This version of SIX12 has removed much
of the prior support for code produced
by BLISS-10, in favor of improvements
to the Bliss-36 support and simplicity
of the implementation of SIX12
functionality.
- 1 -
SIX12 User's Manual Page ii
CHAPTER 1 INTRODUCTION
1.1 ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . 1
1.2 SIX12 OVERVIEW . . . . . . . . . . . . . . . . . . . 1
1.3 ADVANTAGES OF SIX12 OVER DDT . . . . . . . . . . . . 3
1.4 DISADVANTAGES OF SIX12 . . . . . . . . . . . . . . . 3
1.5 CAVEATS FOR BLISS-36 USERS . . . . . . . . . . . . . 4
CHAPTER 2 BASIC SIX12
CHAPTER 3 SIX12 EXPRESSIONS
CHAPTER 4 BASIC BLISS OPERATORS
4.1 ASSIGNMENT IN SIX12 . . . . . . . . . . . . . . . 13
4.2 STRUCTURE ACCESSES . . . . . . . . . . . . . . . . 14
4.3 NUMBERS, NAMES AND STRINGS . . . . . . . . . . . . 14
CHAPTER 5 PEEKING AND POKING
CHAPTER 6 BREAKPOINTING, TRACING
CHAPTER 7 GETTING IN AND OUT OF SIX12
7.1 GETTING IN . . . . . . . . . . . . . . . . . . . . 24
7.2 GETTING OUT . . . . . . . . . . . . . . . . . . . 25
7.3 KNOWING WHERE YOU ARE . . . . . . . . . . . . . . 26
CHAPTER 8 CONCERNING DDT
8.1 CONTROL TRANSFERS BETWEEN SIX12 AND DDT . . . . . 28
8.2 CAUTIONS WITH DDT BREAKPOINTS . . . . . . . . . . 29
8.3 MODIFYING ACS FROM DDT . . . . . . . . . . . . . . 29
CHAPTER 9 CONSOLE INPUT MONITORING
CHAPTER 10 MONITORING VARIABLES
CHAPTER 11 MACROS AND SYMBOL DEFINITION
CHAPTER 12 LINE PRINTER AND DISK I/O
- 2 -
SIX12 User's Manual Page iii
CHAPTER 13 DISPLAY
13.1 DISPLAYING ROUTINE-CALL STACK . . . . . . . . . . 39
13.2 SYMBOL-TABLE SEARCHING . . . . . . . . . . . . . . 40
13.3 EXAMINING THE STATE OF SIX12 . . . . . . . . . . . 41
13.4 WRITING YOUR OWN PARAMETER DISPLAY . . . . . . . . 43
CHAPTER 14 CONDITION HANDLING
CHAPTER 15 APR ERROR RECOVERY
CHAPTER 16 MISCELLANEOUS OPERATORS
CHAPTER 17 USING SIX12
17.1 GENERAL USAGE . . . . . . . . . . . . . . . . . . 51
17.2 LINK-TIME OPTIONS . . . . . . . . . . . . . . . . 52
17.3 TOPS-10 USAGE . . . . . . . . . . . . . . . . . . 52
17.4 SIX12 AND OVERLAYS . . . . . . . . . . . . . . . . 53
17.5 SIX12 AND USER UUO HANDLERS . . . . . . . . . . . 54
CHAPTER 18 DEFINING YOUR OWN OPERATORS
18.1 WHAT DEFINES AN OPERATOR . . . . . . . . . . . . . 56
18.1.1 Important Restriction . . . . . . . . . . . . . 58
18.2 DEFINING OPERATORS FROM SIX12 . . . . . . . . . . 58
18.3 DEFINING OPERATORS FROM A USER PROGRAM . . . . . . 59
APPENDIX A GLOBAL ENTRY POINTS, VALUES AND DATA AREAS
APPENDIX B BUILDING A SIX12
B.1 UNUSUAL REGISTER ALLOCATIONS . . . . . . . . . . . 64
APPENDIX C ERROR MESSAGES
Index
- 3 -
CHAPTER 1
INTRODUCTION
This document is intended as a from-scratch introduction to SIX12, an
extensive debugging aid for Bliss programs on the DEC-System 10/20.
It applies to the version of November, 1981.
1.1 ACKNOWLEDGEMENTS
A great deal of credit for the development of SIX12 goes to R. K.
Johnsson, C. B. Weinstock, W. A. Wulf, T. Lane and J. M. Newcomer, all
from Carnegie-Mellon University (CMU). SIX12 began as a symbolic
debugger for Bliss-10, which was also developed by CMU.
Many of the changes are the work of Ron Brender of Digital Equipment
Corporation. These include the changes for Bliss-36 support and
TOPS-20 I/O, the multiple configurations which produce the several
versions of SIX12 for the cross-product of Bliss-10 and Bliss-36
support for TOPS-10 and TOPS-20 operating systems, cleaned up display
formatting, enhanced displays of status, and the ability to access
actual parameters and local variables.
Joe Newcomer (CMU) added the single-step support, polling override,
module qualification, online help, STORE/RECALL facility, WATCH
command, and condition handling facilities.
This version was re-written in Bliss-36 by Digital. It is supplied
with the BLISS V3 release as a favor to the user-community, and it is
not a supported part of the BLISS product. Most of the Bliss-10
specific support has been removed and a considerable amount of
internal documentation and clean-up has been done.
1.2 SIX12 OVERVIEW
SIX12 is a specialized debugger adapted to the Bliss environment. It
is not intended as a substitute for DDT; the user is expected to link
both with his program and use whichever is more convenient to the need
of the moment. Under this assumption there has been no attempt to
duplicate functions already well-performed by DDT, namely
- 1 -
INTRODUCTION Page 1-2
o breakpointing and tracing at the instruction level.
o symbolic typeout and typein in any mode required (at last
count DDT could display or accept values in over a dozen
different modes).
SIX12 is oriented to the Bliss programming environment in two ways:
o It conforms to Bliss philosophy and notation. A debugging
command is syntactically an expression, which is read in,
evaluated, and the value (if any) printed. However, much
modification has been made to the Bliss syntax in the
interests of flexibility. In particular, an expression is
not required always to yield a fullword value. It may yield
no value, or a vector value of several words. Also the
syntax accepted for operators has been expanded to include
nullary operators, which have no operands, and postfix
operators which follow their operand. For example,
A AND 7 uses the infix operator "*AND*"
. uses the prefix operator "*."
GO uses the nullary operator "*GO*"
137/ uses the postfix operator "*/"
BREAK R1,ERROR,PRINT
uses the prefix operator "*BREAK*", which
accepts a vector operand. A higher-priority
infix operator "*," is used to form the
vector from elementary operands.
(As demonstrated in the last example, with this syntax we can
get by without any keyword forms (for declarations etc.) at
all. To SIX12 everything is an operator or operand. The
user will find it more convenient, of course, to visualize
commands formatted in this way as keyword followed by a list
of arguments.)
o SIX12 is routine-oriented. By this we mean that
breakpointing, tracing, and similar functions dealing with
flow-of-control all occur at the abstract routine level,
rather than at the individual machine instruction level (as
in DDT). In still another way: the smallest unit of code
that SIX12 can see is a Routine. Breakpoints must always be
set at either the entry or exit of a routine, and tracing of
execution is always in terms of routine calls and returns.
DDT is used when code must be dealt with below the routine
level.
- 2 -
INTRODUCTION Page 1-3
1.3 ADVANTAGES OF SIX12 OVER DDT
SIX12 has the following advantages compared to DDT:
1. Source language debugging. SIX12 accepts Bliss-like
notation, and does tracing and breaking in a form easily
relatable to the original source program.
2. Facilities that DDT does not provide, for instance
- the ability to monitor data (not instruction) locations
and report when they are modified,
- the ability to interrupt the program on console input.
If any line-break character (e.g., escape, linefeed,
etc.) is typed while the program is executing (i.e., when
not in TTY input wait), SIX12 will be entered and will
prompt for debugging commands.
3. Extendability. SIX12 permits easy definition of new
operators; in addition simple macros can be defined and used
in expressions.
4. SIX12 can be used to debug in shared high-segments. The
SIX12 linkage has been designed so that two or more people
can be debugging the same or different routines, and still
others running without using the debugger, all in the same
high-segment without interference. DDT breakpoints cannot be
used in shared code.
1.4 DISADVANTAGES OF SIX12
SIX12 has the following disadvantages compared to DDT:
1. No access to program at machine code level.
2. Limited variety of modes for symbolic typeout or typein of
values.
3. Speed, or rather lack of it. SIX12 requires some computation
at every routine call or return, while DDT requires time only
at breakpoints (and less time at that).
4. Space required. SIX12 uses about 18P (9K) in the high
segment and 7P (3.5K) in the low segment, besides the 2K
low-segment space for DDT, and the program-dependent low-seg
space for the symbol table (which, however, is required even
for DDT).
- 3 -
INTRODUCTION Page 1-4
NOTE
The first two of these are alleviated by
the ease with which one can pass from
SIX12 to DDT and back. Thus the full
facilities of DDT are still available to
the SIX12 user.
1.5 CAVEATS FOR BLISS-36 USERS
Although SIX12 has been enhanced for use with Bliss-36, for example,
by extending the syntax of identifiers, the addition of Block and
Blockvector types of access, and condition handling, Bliss-36 users
may be confused by some of the syntactic features of SIX12 which are
based on its original design for use with the Bliss-10 language. Some
equivalents are given in the table below. There are currently no
plans to modify SIX12 to eliminate these inconsistencies.
Bliss-10 Bliss-36 SIX12
-------- -------- -----
"X" %C'X' "X"
'abcde' %ascii 'abcde' 'abcde'
@ . .
#773 %O'773' 773 (base 8)
#773 (base 10)
978 978 #978 (base 8)
978 (base 10)
?.JBREL %name('.JBREL') ?.JBREL
&JBREL
?%CNVR _CNVR _CNVR
%name('%CNVR') ?%CNVR
?$GTMEM $GTMEM $GTMEM
A = 5 A = 5 A = 5
A _ 5
- 4 -
CHAPTER 2
BASIC SIX12
This chapter is a first-time introduction to SIX12, and for details of
the commands you should consult the referenced sections.
You must first compile <at least> your main module with SIX12 linkages
(the DEBUG switch declaration in the module head). Failure to do this
is the most common beginner's error, and results in the runtime
message:
?Halt at user PC <addr> On TOPS-10
or
?Illegal instruction 37000,,<addr> at <addr> On TOPS-20
?Undefined operation code
If you look at the address given, you will find a DEBUG. instruction,
opcode 037 octal. Recompile your main module with the /DEBUG
qualifier and relink your system.
There are many versions of SIX12 which can be linked into your
program. These are selected by such options as TOPS-10 or TOPS-20
support, BLISS36C or BLISS10 linkages, etc. The complete set of
options are described in Appendix C.
Any time you are in SIX12, as indicated by the & prompt, and want to
resume execution of your program, type *GO*. Control returns to your
program where it left off. There are several common ways of entering
SIX12:
1. When your program starts to run, it enters SIX12 before
calling your main routine.
2. If at any time you type a line-terminating character to
TOPS-10 or any character to TOPS-20, SIX12 will take control
at the next routine entry or exit (this can be disabled).
3. A routine entry or exit occurs at which a breakpoint is set.
- 5 -
BASIC SIX12 Page 2-2
The complete list of SIX12 entry and resumption techniques is given in
chapter 7.
The most common operations are examining and modifying locations. The
"*/" operator[1], "*!" operator, and "*." operator all allow you to
examine locations:
&foo/
foo/ 1234 == baz+23
&.foo
1234 == baz+23
&
This shows examining the location whose name is foo. The value is
printed out both in the prevailing radix (normally octal) and in
symbolic form. To examine multiple locations, use the *!* operator
(chapter 5) which takes the number of locations to examine:
&foo!3
foo/ 1234 == baz+23
foo+1/ 0 == 0
foo+2/ 1235 == baz+24
&
To modify a location, use the assignment operator *=* (chapter 5).
Remember Bliss is an expression language, so use parentheses to force
proper evaluation:
&foo = .foo + 5
1241 == baz+30
&(foo+1) = 1
1 == 1
&
Another very common operation is to set breakpoints or trace routines.
To do this, use the *BREAK* or *TRACE* commands; these take the names
of routines to break at or trace:
&break foobar,thud
&trace gorp
&
You can also set a breakpoint or tracepoint after a routine by using
the *ABREAK* or *ATRACE* commands and remove breakpoints or trace
requests by using the *DTRACE*, *DBREAK*, *DATRACE* or *DABREAK*
commands.
You can single-step your program by using the <linefeed> command;
------------------------------
[1] chosen for similarity to DDT
- 6 -
BASIC SIX12 Page 2-3
execution progresses routine-by-routine for each <linefeed> given. If
you get to some routine entry and know that nothing interesting is
going to happen (say, an output routine), use the *OK* command to
execute that routine and all the ones it calls without single-stepping
thru them. You will get control at the next breakpoint or at the end
of the routine you give the *OK* to, whichever comes first.
The complete list of breakpointing and tracing options is given in
chapter 6.
When you are at a breakpoint, the *CALLS* operator will print the
entire call stack; or use *CALL* <n> to print out the <n> most recent
calls on the stack. Complete details of displaying information are
given in chapter 13.
The *MONITOR* command lets you "continuously" check several locations
to see if they change (the check actually occurs at every routine
entry and exit). See chapter 10.
The *WHERE* command lets you find out the module and location of some
octal value (such as is printed out when an illegal memory reference
is taken).
You now have enough information to start successfully using SIX12.
- 7 -
CHAPTER 3
SIX12 EXPRESSIONS
At the lexical level, SIX12 treats lower case and upper case
identically, so commands may be typed in either case or a mixture of
both. In addition, SIX12 will recognize any unique abbreviation (two
characters minimum) for any of its alphabetic operators. Thus, all of
the lines below say the same thing:
IF |.A LSS .B| BREAK FOO,BAZ
if |.a lss .b| break foo,baz
if |.a ls .b| BREAK foo,baz
if |.a ls .b| br foo,baz
SIX12 contains a fairly intelligent syntax analyzer/evaluator which
can evaluate quite complex expressions. For instance, all of the
following are legal Bliss expressions; they are also legal in SIX12
and would produce the same result.
.ALPHA
SUM = .SUM + 3
NOT .FLAGS<1,1>
MYROUTINE (7, .B, XYZ())
SUM = 0; COUNT = .COUNT + 1
The syntax analyzer recognizes two classes of objects: operators and
operands. The meaning of operators is not built into the analyzer,
but is defined by a table of routines which are to be called to
evaluate them. This makes it simple to add new operators or redefine
old ones; this can even be done at runtime if the necessary routines
are compiled and linked separately with SIX12. (The methods for
defining your own operators are discussed later; we assume everywhere
in this document that you have not tampered with any standard
operators.) The meaning of operands, however, is built into the
analyzer. The possible types of operand are
<number> <string> <symbol>
- 8 -
SIX12 EXPRESSIONS Page 3-2
A <number> is a sequence of digits, possibly preceded by a number sign
*#. Its value is the equivalent signed, two's complement binary
integer. The number is assumed to be written in the default radix or
base, which can be set or examined by the standard operator *BASE*.
The escape character *# is provided to ease the use of two radices: a
number preceded by *#* is taken to be written in octal radix
regardless of the default radix, unless the default radix is octal, in
which case the number is taken as decimal. For example,
Default Radix Input Value
------------- ----- -----
10 (decimal) 34 000042 octal
10 #34 000034 octal
2 (binary) 10110 000026 octal
2 #34 000034 octal
8 ( octal) 34 000034 octal
8 #34 000042 octal
Thus when the default base is decimal, this is the same as the
Bliss-10 source convention. When SIX12 is initialized, the default
base is octal (as with DDT).
Strings are entered as
'string' or "string"
corresponding to left- and right-adjusted ASCII strings respectively.
In either type of string the other string delimiter can appear freely,
and double occurrences of the string delimiting character are used to
denote it once. This is precisely the same as the Bliss-10
convention. However, note the following differences:
o ? is not implemented as an escape character (not relevant
for Bliss-36 users).
o Carriage return cannot appear in a string; it terminates the
string just as if the matching delimiter had been encountered
(CR or LF always terminate debug input expressions).
o %RADIX50_10, %ASCIZ and %SIXBIT stringtype converters have
not been implemented. (They could be easily included by
defining appropriate operators).
Examples:
'HI!' "Q" 'a CR or LF terminates me anyway
A long-string, as in the last example, generates a vector value which
may be larger than a bliss-value. This is most useful in conjunction
with user-defined operators. (See chapter 18)
- 9 -
SIX12 EXPRESSIONS Page 3-3
Symbols are the most complex type of operand. A symbol is looked up
in the Linker-generated symbol table, and its value is the value
entered for it in the table. Thus a name is an address, as in Bliss.
DDT has a complex search convention to deal with the problem of
multiply defined symbols (which exists because the table only contains
six characters of a name, and/or because the same local name can be
defined in many modules). SIX12 uses this much simpler rule:
identical symbols are implicitly numbered in the order in which they
are linked. If there exists more than one symbol with the same name,
the name must be "qualified", either suffixed by *%*n, where n is the
ordinal you want, or prefixed with a module name if the name is unique
within that module. This is discussed in detail in section 4.3
Examples:
HELPME Value of the symbol 'HELPME'
LOTSOFME%5 Value of fifth symbol 'LOTSOF'
FOO\LOTSOF Value of 'LOTSOF' in module 'FOO'
LOTSOFME Error - ambiguous
There are symbol table searchers included in the standard set of
operators to help you decide which ordinal you want, or remember what
name you need in the first place. See chapter 13. Since names
(letter-digit strings) can also refer to operators (e.g., *AND* *OR*)
the *%*-convention is also used to distinguish symbols from operators.
An unadorned name is first searched for in the macro table, then in
the table of operators, and finally in the symbol table, taking the
first match in the process. However, <name>*%*<n> (for <n> greater
than 0) is only searched for in the symbol table. Thus "*OR%1*"
always gets you the symbol "*OR*" but "*OR*" is taken for the operator
*OR*. Since Bliss-36 maps underscore ("_") into percent ("%") and
period (".") into dollar-sign ("$"), SIX12 also performs this
conversion. Thus, if you declare
OWN
meta_1 ;
DDT will display this as "META%1", while SIX12 will know this symbol
as "META_1". The SIX12 symbol "META%1" refers to a different symbol,
namely the first occurance of "META" in the DDT symbol table.
Further note
The only source of program symbols that
SIX12 has is the Linker symbol table
(also used by DDT). Therefore, locals,
formals, structures, and so on are
unknown to SIX12. Only GLOBAL, OWN,
link-time constant BIND, ROUTINE and
MODULE names will be present in the
table.
- 10 -
SIX12 EXPRESSIONS Page 3-4
We have now fully discussed operands, and turn to the operators which
work upon them. Operators are denoted either by names (e.g., *GEQ*,
*BREAK*) or by special characters (e.g., *% + *).
In the latter category, *' " # %* <space> <tab> <CR> <LF> may not name
operators. The syntax analyzer distinguishes four syntactic types of
operators, namely
Nullary, having no operands: <operator>
Prefix, preceding its operand: <operator> <operand>
Postfix, following its operand: <operand> <operator>
Infix, having both operands: <operand> <operator> <operand>
The same symbol may represent more than one operator in different
parses. For example
+ E
E + F
show "*+*" in prefix and infix parses; these two instances will
actually result in the invocation of two different routines to
evaluate "*+*". In theory the same symbol could be given all four
parses, invoking one to four different routines; in practice this is
a poor idea. An operator with more than one parse can introduce
ambiguity: the classic case is with "*/*", which in the standard
definition has postfix ("*A/*" prints contents of A, as DDT would) and
infix ("*A/B*" does division) parses. Now, does
A/-N
invoke postfix "*/*" followed by infix *"*-*"*, or prefix *"*-*"*
followed by infix "*/*"? With the definitions given above the second
is clearly the correct choice, but the analyzer can hardly be expected
to know that. In point of fact this will be evaluated in the first
way, due solely to an arbitrary design decision. The moral of this
story is that the analyzer cannot be expected to always do the right
thing. It works fine for pure Bliss expressions; a key thing is to
be wary of using expressions which yield a null value (as *x/* does)
in larger expressions. The analyzer assumes that operators will yield
a value, and gets confused when they don't (since its assumptions
about the parsing of subsequent operators must be junked). If an
expression with side-effects blows up, always check to see how much of
it had already been evaluated. Two good rules to keep out of trouble
are 1) parentheses can fix lots of things, and 2) avoid semicolons -
you can afford to do it on two lines.
With these words of warning we pass to a description of the standard
set of operators. This is the meat of what you can do with SIX12.
- 11 -
CHAPTER 4
BASIC BLISS OPERATORS
We do not pretend to have implemented a Bliss interpreter. However, a
fair subset of the simple expressions (*not* control expressions) is
available, and more could be implemented if you need it. The
following operators are defined exactly as in Bliss:
+ - for example -E1 E2+E3
* / as A*B (beware of E/, which is not an error)
^ as in A^B (shift) [1]
( ) as in Bliss:
AND NOT OR logical operators
GEQ thru LSS relational operators
(<expr>) Grouping indicator
or as routine callers
<expr>(<list>) Routine call
For instance
5*(.ALPHA-1)
MYROUTN(41, .PARM)
(.RTNVEC[.I])(.parm1+5,22)
The value of the second expression is the value returned by calling
------------------------------
[1] In Bliss-36, *^* is a logical shift left and an arithmetic shift
right. SIX12 does the appropriate shift.
- 12 -
BASIC BLISS OPERATORS Page 4-2
the routine *MYROUT* with two actuals. The value of the last
expression is the value returned by calling the routine named in the
i+[th] position of RTNVEC with the parameters indicated.
*< >* have the same meaning, of creating a byte pointer.
However, sign-extension is not accepted; there must be
exactly two values within the brackets, i.e.
[addr]<[position],[size]>
is the only allowable syntax for them.
. performs the same function, 'contents', as in Bliss.
= performs the same function, 'store', as in Bliss. For
instance
.A1
.FLAG<17,1>
SE = .SE * 200
FOO = .A1 + 23
You should be aware, however, of a difference, discussed below
in section 4.1
[ ] Perform structure access for simple structures.
4.1 ASSIGNMENT IN SIX12
SIX12 evaluates names as addresses, just like Bliss-36. Because of
its Bliss-10 origins, if the left half of a pointer word is zero, it
is treated as a fullword pointer in dot or assignment contexts, but
words with nonzero left halves are taken as true byte pointers.
Extended Addressing Limitation
Thus, SIX12 is guaranteed to break in
the presence of extended addressing.
(The same applies to the *MONITOR*/*WATCH* operation, which may be
given either word addresses or byte pointers). The only way this will
be noticeable to the user is that sometimes *dot* will act like a
CH$RCHAR, and = will act like a CH$WCHAR.
In Bliss-10, *.41* will yield zero every time (being equivalent to
*.41<0,0>*) but in Bliss-36 or SIX12 it will yield the contents of
word *41* (corresponding to *@41* in Bliss-10). Similarly for
*41 = E*. Also, to get Bliss-10 semantics for *A = B*, it must be
written *A = B<0,36>*.
- 13 -
BASIC BLISS OPERATORS Page 4-3
If an attempt is made to fetch from or store into an address not in
the user's address space, SIX12 will detect this and report the
illegal address.
TOPS-20 Difference
Because of the way TOPS-20 deals with
"create on reference" pages, SIX12 may
report an illegal address if you attempt
to access static storage (using SIX12's
fetch or store operators) before your
program has "referenced" the memory
involved. SIX12 detects illegal
addresses by asking the monitor if the
pages are "readable" using the RPACS
JSYS. If the page has not been
referenced yet, RPACS will return
"doesn't exist".
4.2 STRUCTURE ACCESSES
Brackets *[ ]* with a single parameter do a structure access according
to the standard VECTOR structure. Hence *E1[E2]* is equivalent to
*(E1+E2)<0,36>*.
Brackets with three parameters do a structure access according to the
standard Bliss-36 BLOCK structure, and those with four parameters do a
structure access according to the Bliss-36 BLOCKVECTOR structure.
In addition, if the user sets the contents of *SIXREF* to a true
value, the access will be done as a REF-structure rather than a
structure access.
Perhaps someday we will get structure information from the compiler...
4.3 NUMBERS, NAMES AND STRINGS
<number> A number is a sequence of digits interpreted in the
current radix (initially base 8). See chapter 16.
#<number> A number preceded by a *#* changes to the "other"
radix, i.e., if in base 8, the number is interpreted
in base 10; if in base 10, it is interpreted in base
8. If the default base is neither decimal nor octal,
the # indicates octal radix. See chapter 16.
<number> %A Refers to the address of the n'th actual parameter of
- 14 -
BASIC BLISS OPERATORS Page 4-4
the current routine (when stopped at routine entry or
exit).
In the example below, the break at routine "TestZero"
will occur only if the first actual parameter is zero.
&if |.1%A eql 0| BREAK TestZero
<number> %L Refers to the n'th local word of the stack frame of
the current routine. Local words include any saved
register values, stack management control words, etc.
that may be allocated after the frame pointer.
Consequently, a machine code listing might be required
to determine the actual correct offset for a local
variable. In particular, Bliss-36 may allocate local
variables to the registers.
<name> A name is 1 to 6 characters from the set "*A" - "*Z",
"*a" - "*z", "*0" - "*9", "$", "&", "*_". The first
character must not be a digit. Characters after the
first six are not used for name resolution. Lower
case letters are converted to uppercase, "&" is
converted to "." and "_" is converted to "%". This
conversion is used in the Bliss-36 compiler to
translate "_" into a character acceptable in RADIX50.
Names are looked up in one of three symbol tables in
this order:
1. The SIX12 macro table
2. the SIX12 operator/command table
3. the DDT symbol table
In the case of multiple DDT symbol tables, where one
is in the TOPS-10 high segment and another is in the
TOPS-10 low segment, there are more complex rules for
symbol resolution in the DDT symbol table. See
section 17.4. The value of a name is the address or
offset obtained from the DDT symbol table. (Module
names, which also occur in the DDT symbol table, are
ignored during name lookup).
?<name> ? allows the name which follows to include the
characters
"." and "%", so the transliteration of "$" is
converted to "." and "_" is converted to "%" . Names
are typed out using "." and "_".
Names are looked up in one of three symbol tables in
this order:
- 15 -
BASIC BLISS OPERATORS Page 4-5
1. The SIX12 macro table
2. the SIX12 operator/command table
3. the DDT symbol table
In the case of multiple DDT symbol tables, where one
is in the TOPS-10 high segment and another is in the
TOPS-10 low segment, there are more complex rules for
symbol resolution in the DDT symbol table. See
section 17.4. The value of a name is the address or
offset obtained from the DDT symbol table. (Module
names, which also occur in the DDT symbol table, are
ignored during name lookup). ("&" and "_") need not
be used. If %n is used after such a name to
disambiguate it, a space must separate the %n from the
name. The name may also begin with a digit, e.g.
"?01$A" is recognized as an identifier.
&?.JBSYM
116 == 116
&.?.JBSYM
-447765030 == 777330,,PAT..+100
name %n Refers to the n'th entry in the DDT symbol table for
the name (for "n" greater than zero). (Module names
are ignored and not counted). If a name is unique
within a module, it may be qualified with the "\"
qualifier (see below). A name which is qualified with
"\" may not be further qualified with "%".
name %0 Refers to the SIX12 command or operator with the given
name. This is required when a macro definition
conflicts with a SIX12 operator name, and the operator
name is required.
module\name Qualifies a name to lie within a module. Thus, if the
name is unique in the module, qualification with "%"
(see above) is not required. The rules for simple
names (e.g., the use of "?" to enable the use of
special characters in the name) apply to both the
module name and the symbol name. If a QUALIFY command
(see chapter 16) is given, the module name (but not
the \) may be omitted.
&C
.^
Multiple entries in DDT symbol table for C
&PRS C
C%1 400360 Own SIG Routine
C%2 5645 Own FOO.. 0
&SIG\C
400360 == C
- 16 -
BASIC BLISS OPERATORS Page 4-6
Using default qualification to search the SIG module's
DDT symbol-table would be done with
&QUALIFY SIG
&\C
400360 == C
&?FOO..\C
5645 == C
- 17 -
CHAPTER 5
PEEKING AND POKING
One basic requirement on a debugger is the ability to examine and
modify program locations.
The only standard operator for changing memory locations is assignment
(=), which should need no explanation. We should point out, however,
that SIX12 never associates from right to left. Therefore,
A = B = C = 0
will not work in SIX12. In order to discourage accidental use of this
construct, the assignment operator is defined to have no value. In
the example above, the address of B would be stored into A, then a
syntax error would occur since the second = would have no left
operand.
One Bliss-compatible method for examination of program locations is
provided by the dot *. operator. As we mentioned in passing
previously, SIX12 prints out the result of every evaluated expression.
Thus one need only type .ALPHA to see the contents of ALPHA; for
example, a terminal interaction could look like this:
&.FLAGS,.PNTR
677 == 677
5737 == FFAREA+5
(Note: & is SIX12's prompt character).
A DDT-like notation has also been implemented. The operator "/", used
in a postfix fashion, prints out the contents of the fullword whose
address is its argument:
&STACKCNT/
STACKC/ 566005322 == 566,,SPACE+203
The infix operator "*!" does the same thing for a consecutive set of
words; A*!n prints n words beginning at A. For example:
- 18 -
PEEKING AND POKING Page 5-2
&BUFF!3
BUFF/ 57 == 57
BUFF+1/ 122 == 122
BUFF+2/ 0 == 0
In addition, unless the user has explicitly disabled console polling
(see chapter 9), typing any line termination character (TOPS-10) or
any character (TOPS-20) will terminate long typeouts.
In all cases, values or contents are first printed numerically (in the
default radix), then in symbolic halfword format (like DDT $R $H;
offsets are in the default radix). Whenever the left half looks like
an "interesting" byte pointer[1], the byte pointer values are printed
out in decimal following the symbolic name. If the default BASE of 8
is used, a # will precede the values of the position or size
designators if they are greater than 7.
&IBUFPTR/
IBUFPT/ 4400017360 == IDTREE+316,,BUF+4<0,#36>
When an address is given which is outside the user's address space, a
? is printed as a value; for multiword displays, the displaying
ceases.
&?.JBREL/
.JBREL/ 34177 == 34177
&35000/
35000/ ?
&34176!200
34176/ 0
34177/ 0
35000/ ?
&
------------------------------
[1] The definition of "interesting" is subject to change, but
presently includes such things as <n,7>, <n,8>, <n,9>, <0,18>,
<18,18> and <0,36>.
- 19 -
CHAPTER 6
BREAKPOINTING, TRACING
The other basic requirement for a debugger is the ability to trace
execution of a program and stop it ('break') where necessary. As we
said earlier, SIX12 does this on a routine level. The operators are
given in terms of setting (and later clearing) actions on routines.
Any of these actions may be set conditionally. Conditions are fully
general because they are given as SIX12 expressions. When required,
the text given is evaluated; it must yield 1 in the low-order bit of
its value for the action to be taken. (If the expression yields a
vector value, only the first word is considered; a test which yields
a null value always fails.) For instance, simple conditions might be
.FLAGS<17,1>
or
.CCOUNT GTR 0
Note: it should be apparent that setting a conditional action on a
frequently- called routine can cause substantial overhead and
significantly degrade execution speed. For simple conditions such as
the examples, a conditional breakpoint for which the condition is
satisfied executes about 8500 instructions between the breakpoint
instruction and requesting input from the user; a conditional
breakpoint for which the condition is not satisfied executes about
2500 instructions.
The standard syntax for setting unconditional actions is
action-name listofroutines
e.g.,
BREAK R2,PRINT,ERR3
The syntax for setting conditional actions is
IF |text of condition test| action-name listofroutines
e.g.,
IF |.VALUE<10,1>| TRACE TESTIT
where "|" delimits the text which is saved for evaluation. (The $
character could also be used, but you can't backspace over it). Two
notes: IF is a noise word and can be dropped. Commas in a list of
routines can be replaced by spaces. Never drop commas surrounding
- 20 -
BREAKPOINTING, TRACING Page 6-2
anything but a simple operand (number,symbol). Thus, in
TRACE T34, .PNTR, EXIT
the commas are necessary, but they aren't for
TRACE T34 EXIT METOO
The same applies to commas anywhere else in SIX12 (e.g., routine
calls).
The syntax for clearing actions is
Daction-name listofroutines
i.e. same mnemonic with D prefixed, as
DBREAK ZURICH
This clears either conditional or unconditional action. The actions
and conditions for them may be examined with the PRINT ACTION command.
Conditional and unconditional actions do not coexist. There cannot be
both conditional and unconditional instances of a given action on a
given routine, nor can there be more than one condition governing a
given action on a given routine. Thus, if a conditional or
unconditional break is set on a routine, any previously set break of
any type on the same routine is cleared, but other actions, say trace,
on that routine are unaffected.
For actions which take place after a routine has executed, the value
of the routine may be tested. Normally this is in the VREG, but from
SIX12 it must be accessed as the variable SIXVREG, e.g.,
&if |.sixvreg eql 0| abreak getpointer
The possible actions are:
BREAK list Stop execution at routine entry, with the message
<=> At: routine from call-loc
Actuals: values
ABREAK list Stop execution at routine exit, with the message
<=> After: routine Value: value == symbolic
DABREAK list Remove ABREAKs from the routines listed.
DBREAK list Remove BREAKs from the routines listed.
TRACE list Prints a message when routine is entered or left
- 21 -
BREAKPOINTING, TRACING Page 6-3
without breaking. The messages look like this:
--> routine from call-loc
Actuals: values
<-- routine Value: value == symbolic
TRACE AFTER list
Initiates trace mode when the routine is entered, so
that all routine calls and returns are traced until
the routine is exited. The original routine call and
return are not traced. (No, Virginia, it won't screw
up if the routine is recursive!)
TRACE FROM list
Equivalent to TRACE plus TRACE AFTER; thus the
routine and its subroutines are traced.
DTRACE list Remove TRACEs from the routines listed.
DTRACE FROM list
Remove TRACE FROMs from the routines listed.
DTRACE AFTER list
Remove TRACE AFTERs from the routines listed.
OPAQUE list Tracing and single-stepping are turned off when an
OPAQUE routine is entered, and remain off until the
matching exit. This lends a degree of abstraction to
tracing and single-stepping. OPAQUE 'outranks' TRACE;
thus, even if routines with TRACEs set on them are
called within the scope of an OPAQUE, they are not
traced.
OPAQUE AFTER list
This does OPAQUE except that the routine itself is
traced. Since we know that no trace printout will be
required between entry and exit, paper is conserved by
not printing a separate tracing notice for exit:
--> routine from call-loc
Actuals: values Value: value == symbolic
(assuming of course that tracing was on when the
routine was entered).
DOPAQUE list Remove OPAQUEs from the routines listed.
DOPAQUE AFTER list
Remove OPAQUE AFTERs from the routines listed.
COPAQUE This command sets an internal switch so that calls
made on user routines from SIX12 will not be traced
even if SETTRACE is in effect. This is useful when
the user has debug-printout routines which are called
- 22 -
BREAKPOINTING, TRACING Page 6-4
from SIX12, or has user-defined operator routines
which are called from SIX12. If SETTRACE is in
effect, it is turned off for the duration of the call.
By default, the COPAQUE switch is normally turned off,
and must be set by the user.
NOCOPAQUE This command resets the internal switch to its default
value set at initialization, so that calls on routines
made from SIX12 will be traced if a SETTRACE is in
effect.
TRACE, TRACE AFTER, TRACE FROM, OPAQUE and OPAQUE AFTER control the
trace facility during program execution. The user may turn tracing on
or off by means of the SETTRACE, CLRTRACE, GOTRACE, and GOCLR
operators, overriding OPAQUEs or TRACEs. (see Getting In and Out of
SIX12, chapter 7). (The TRACE and OPAQUE operators merely set or
reset a switch controlling the printing of trace output. The user can
set or clear this switch before resuming program execution.)
NOTE
Conditional actions set on routine exits
may need to test the value which the
routine is returning. This value is
available as the contents of the global
SIXVREG. In general, the user should
never attempt to access any registers
directly in SIX12 expressions. However,
SIXVREG can be treated the same as the
VREG (e.g., it can be modified, and the
new value will be in the VREG when
program execution resumes).
Conditionals may also be used to modify the execution of a program in
certain restricted ways. For example, consider a routine MOVEIT which
is given a pointer to a value, but is expecting a value (as, for
example, might be caused by calling it passing the name of a variable
instead of its contents). This situation may be rectified as follows:
&if |(1%A = ..1%A; 0)| break moveit
The compound expression assigns to the first parameter the contents of
the word pointed to by the first parameter, and then returns a false
value, so the break does not actually take effect.
It is not possible, however, to conditionally take actions, for
example, to assign the value 10 to a variable if its value is greater
than 62. Nonetheless, this technique with conditionals sometimes
saves a lengthy recompilation to fix a simple error.
- 23 -
CHAPTER 7
GETTING IN AND OUT OF SIX12
By getting into SIX12 we mean stopping execution of the user program
and causing SIX12 to begin reading and executing user commands.
Getting out is the reverse process of resuming user execution.
7.1 GETTING IN
- One method of entering SIX12 during execution is through a
(previously set) breakpoint; see chapter 6.
- Another is through a break caused by terminal input
monitoring, or the MONITOR (of data locations) operation.
See chapter 9 and chapter 10.
- You can enter SIX12 before program execution begins (but
after stack initialization) by entering DDT and setting
SIXSTA (STARTFLG in module SIX12) to 1. Normally SIXSTA
(STARTFLG) is set to a true value, so SIX12 will normally be
entered when execution commences. However, if it has been
set to a false value (see section 17.2), it may be set true
again by the following:
.get program
.ddt
sixsta! 1 <cr>
$G
SIX12 V8-4 (TOPS-10 I/O) for Bliss-36
&
Here $ = <escape>, and & is SIX12's prompt for an input. Of
course, you could also force an exit after making the patch
and save the core image.
- You can get into SIX12 from DDT by
SIXDDT$G.
See Concerning DDT, chapter 8.
- 24 -
GETTING IN AND OUT OF SIX12 Page 7-2
- You can explicitly call SIX12 from your program. Call the
external name "SIX12" with one parameter, e.g.,
external routine SIX12;
SIX12( 123 ); ! Fall into Debugger at command-level.
SIX12 prints the parameter value and stop location:
PAUSE 123 AT <location>
&
7.2 GETTING OUT
Getting out of SIX12 is accomplished by executing one of 3 operators:
GO resumes user program without any special action.
GOTRACE turns on tracing before starting. This cancels the
effect of any active OPAQUE. Equivalent to typing a
SETTRACE and a GO.
GOCLR turns off tracing before starting; equivalent to
giving CLRTRACE and a GO.
RETURN expression
The action of this depends on how you got into SIX12.
- If you entered by setting SIXSTA (STARTFLAG) and
having SIX12 recognize this at program entry, then
the expression becomes the value of the CCL flag.
- If you entered by an explicit call on SIX12, the
expression is the value of the SIX12(x)
expression.
- If you are at a routine exit, by either setting an
ABREAK (including implicit ABREAKs set by STEP and
OK), or by MONITOR detecting a change in a
variable or by console polling, then the
expression becomes the value returned by the
routine.
- If you are at a routine entry, either by a BREAK
(including implicit BREAKs set by STEP) or by
MONITOR detecting a change of a value or by
console polling, then the execution of the routine
is suppressed. Control returns to its caller with
the value of the expression. Thus RETURN is
useful for hand- simulating unwritten or
malfunctioning code.
- 25 -
GETTING IN AND OUT OF SIX12 Page 7-3
STEP
<line-feed> This effectively sets an ABREAK at the current
routine, and a BREAK at every routine which may be
called from the current routine, then allows execution
to proceed much as GO does. This command allows you
to single-step through the program. Typing <linefeed>
will have the same effect. If single-step execution
reaches a routine which is OPAQUE, the single-step
breakpoints are suppressed until control returns from
that routine. This is extremely convenient for the
same reasons OPAQUE is useful for tracing.
OK This effectively sets an ABREAK at the current
routine, and then allows execution to proceed much as
GO does. This command, particularly in conjunction
with STEP, allows you to avoid single-stepping through
a routine you know already works.
7.3 KNOWING WHERE YOU ARE
SIX12 prompts with an ampersand character, &. In addition, assorted
status may appear with the prompt:
- On nested SIX12 calls, the depth of nesting in SIX12 is
printed,
4:&
which indicates that this is the fourth recursive call of
SIX12. The first level of call would be shown as "1:" except
this is so common that the number is suppressed.
- If output is going to the line printer (see section 12) and
not to the terminal, a "-" is printed to the left of the "&"
2:-&
This is so you don't wonder why SIX12 has suddenly stopped
printing. If LPTDUP is set, so that output goes to both the
terminal and the line printer, then the "-" is not printed.
- If NODEBUG mode is set (chapter 16), an N will print to the
left, indicating you are in NODEBUG mode. In addition,
certain commands will issue a warning message when they are
executed.
- 26 -
GETTING IN AND OUT OF SIX12 Page 7-4
4:-N&break foo
Warning: You are in NODEBUG mode
4:-N&ok
Operation makes no sense in NODEBUG mode
4:-N&debug
4:-&
- 27 -
CHAPTER 8
CONCERNING DDT
8.1 CONTROL TRANSFERS BETWEEN SIX12 AND DDT
We have not tried to duplicate the many useful facilities already
available in DDT. Instead, we have implemented easy transfers between
SIX12 and DDT.
You can get into DDT[1] from SIX12 by issuing the command
DDT
To return to SIX12, type SIXRET$X to DDT.
If you are in DDT but you didn't get there from SIX12, you can enter
SIX12 by typing
SIXDDT$G
Subsequently issuing GO to SIX12 returns you to DDT. (Clearly, you
must not do this if the stack has been destroyed.)
A valid stack must be available before calling SIXDDT. If necessary,
this can be set using the global symbol SIXSP.
SIXSP/ 0 -200,,STACK
will set up a stack of 200 (octal) words at location STACK.
Once a stack has been set up, SIX12 may be called. If SIX12 has not
been initialized, you must initialize it by calling one of the
routines SIX10, SIX36C or SIX36, depending upon the version of SIX12
in use. If you enter SIX12 by letting SIXSTA (STARTFLG) have a "true"
value, then SIX12 is automatically initialized for you. (It may be
necessary to set up a stack even if SIX12 has been initialized, for
------------------------------
[1] In TOPS-10, you must have linked DDT into your program with the
/DEBUG linker switch. On TOPS-20, if nothing is mapped at 770000
(octal), SYS:UDDT.EXE is dynamically merged into your address
space.
- 28 -
CONCERNING DDT Page 8-2
example, if the stack pointer register has been inadvertently
destroyed).
8.2 CAUTIONS WITH DDT BREAKPOINTS
The SIX12 linkage in Bliss-36 produces the following instructions at
the head of each routine
DEBUG. routine
CAI n
; n instructions for routine setup
If you set a DDT breakpoint at any of the n instructions following the
CAI instruction, it will not be seen. [2] Therefore, to set a
breakpoint early in the routine, you must set it somewhere after the n
instructions following the CAI.
8.3 MODIFYING ACS FROM DDT
If you enter DDT via SIX12's DDT command, the user program ACs are not
available. Instead, the ACs contain information peculiar to SIX12.
These ACs may be arbitrarily destroyed while inside SIX12, as SIX12
preserves them before it transfers control into DDT and restores them
when you return via the SIXRET$X DDT command.
To modify the user program ACs, it is necessary to set a DDT
breakpoint and modify the ACs at that point.
------------------------------
[2] This is done by black magic; what appears to happen is that DDT
will not take a breakpoint instruction which is executed because
it is the target of an XCT instruction, and SIX12 uses an XCT
instruction to execute the first n instructions of the routine
setup. Other explanations may apply. This explanation is not
warranted against defects.
- 29 -
CHAPTER 9
CONSOLE INPUT MONITORING
If a line termination character is typed when the program is not in a
TTY input wait, SIX12 will shortly fake a breakpoint at some routine
entry or exit, and process the line as command input. Unlike earlier
versions of SIX12, TOPS-10 does this on a line, rather than character,
basis. TOPS-20 does it on a character basis. In addition, long
typeouts from some operators, such as !, will be terminated by typing
a line termination (TOPS-10) or any (TOPS-20) character. This
monitoring is the normal state for SIX12. It can be disabled,
permitting type-ahead, by the *DISABLE* operator but will be
automatically re-enabled whenever a break occurs (for some other
reason, of course). If you issue DISABLE and subsequently regret it
(e.g., get caught in an endless loop), you can re-enable monitoring by
entering DDT and setting SIXENB (ENABFLG in module SIX12) to 1; the
normal procedure is
^C
^C
^T
<message with interrupted PC value - remember this!>
.DDT
SIXENB! 1 <cr>
<PC-value>$G
<CR>
&
Here $ = <escape>; & is SIX12's prompt for an input.
To permanently disable polling, the *POLLOFF* command can be
issued.This permanent disabling can be reset by issuing the *POLLON*
command.Usually, the purpose of this is so a system can be released to
users with SIX12 still present (very useful for experimental systems).
The SIXNPL (NOPOLLFLG) flag controlled by POLLON and POLLOFF can also
be set with DDT, so the typical way of setting a file up for users is
.get MYPROG
.DDT
SIXNPL/ 0 1<cr>
- 30 -
CONSOLE INPUT MONITORING Page 9-2
SIXSTA/ -1 0<cr>
calli 12$X
EXIT
.SAV (or SSAV, or NSAV or NSSAVE)
MYPROG saved
.
The primary distinction between DISABLE and POLLOFF is that DISABLE
disables console polling only until the next SIX12 event which calls
the SIX12 command interpreter, at which point polling is re-enabled,
while POLLOFF absolutely positively disables console polling until
SIXNPL is reset either with DDT or the POLLON command.
- 31 -
CHAPTER 10
MONITORING VARIABLES
SIX12 can keep track of the contents of specified program locations,
and report when they change. The contents of each location being
monitored are compared against its last reported contents at every
routine call and return. When any changes are found, SIX12 reports
them and, if requested, stops program execution (the same as a
breakpoint). The monitoring message is one of
*** Before routine-name from caller at an entry
*** During routine-name at an exit
followed by a list of changes found, in the format
M- location Old: oldvalue New: newvalue
W- location Old: oldvalue New: newvalue
where "M-" indicates the variable was detected by a MONITOR command,
and "W-" indicates the variable was detected by a WATCH command. If
any MONITOR variable changed, SIX12 stops and enters command mode; if
all the variables were selected by WATCH, SIX12 continues executing.
The syntax for requesting monitoring is
MONITOR listoflocations
WATCH listoflocations
where each location may be a word address or a byte pointer, as in
MONITOR ACCUM, BUFHDR<0,#18>, FLAGS<#30,1>, 41
The syntax for stopping monitoring is
DMONITOR listoflocations
DWATCH listoflocations
For example, the request shown could lead to a message as follows:
*** During GETCHR
M- ACCUM Old: 122 New: 56
M- FLAGS<#30,1> Old: 1 New: 0
&
- 32 -
MONITORING VARIABLES Page 10-2
where & indicates that SIX12 is waiting for a command. When the user
issues GO, execution will proceed from the exit of GETCHR.
NOTE
Values are always printed in the default
radix. When a monitoring request is not
for a fullword, the position and size
fields are printed in decimal.
The variables being monitored and their current "old values" can be
examined using the PRINT MONITOR command; see chapter 13.
The DMONITOR and DWATCH commands are identical, and can be used
interchangeably; DWATCH was added for symmetry and completeness.
It is not necessary to DMONITOR a location in order to WATCH it, or
DWATCH it in order to MONITOR it. The MONITOR and WATCH commands, if
the location is already defined in the table, will change the flag
indicating whether it is a monitored or watched location.
- 33 -
CHAPTER 11
MACROS AND SYMBOL DEFINITION
As a more or less free spin-off from conditional actions, we have
implemented simple text substitution macros (no arguments at present).
The format for defining a macro is
MACRO name=|macro text|
where "|" delimits the macro text on both sides (the <ESC> character
could also be used, but you can't backspace over it). The macro is
invoked merely by writing its name, as in
&MACRO CALLR=|R4P(.A, #37)|
&RESULT = CALLR
&CALLR
5004 == BUFFER+345
Macros can be deleted by the operator
FORGET listofnames
e.g.,
&FORGET CALLR
Space for the text is not reclaimed. See Disk I/O, chapter 12, for a
recovery method if you run out of text space. The PRINT MACRO
operation can be used to examine the text of a macro; see chapter 13.
Macro names always have precedence over both operators and symbols;
but a name followed by %n is never taken to be a macro.
New entries can be made in the DDT symbol table; these names will
also be available to DDT. The format is
BIND name = expression
The name is defined as a global (in module PAT..) with value that of
the result of evaluating the expression. For example,
&BIND POINT= .PNTR
&POINT
- 34 -
MACROS AND SYMBOL DEFINITION Page 11-2
1234567 == 1,,234567
&DDT
POINT=1,,234567 $P
&
The BIND operation should be used rather than MACRO to define a name
with a constant value, as table lookup is much faster than macro
substitution. BIND is a good way to create debugging temporaries with
user-specified names. For example,
&BIND MYTEMP = .?.JBFF<0,#18>; ?.JBFF = .?.JBFF + 1
or
&BIND DBGCHR= SIXPAT[2]
(SIXPAT[2] names the third of a set of temporary locations set aside
in SIX12 for debugging use. See Appendix A).
The values of all of the BIND declarations may be seen by using the
PRM operator (chapter 13) to print out the module PAT...
&PRM ?PAT..
PAT.. 6214 Module 4 symbols
POINT 234567 Global PAT..
MYTEMP 34144 Global PAT.. 0
DBGCHR 17622 Global PAT.. 176
- 35 -
CHAPTER 12
LINE PRINTER AND DISK I/O
Normally, all output from SIX12 is directed to the user's terminal.
Under certain circumstances (such as when tracing, or dumping a large
area of memory), it may be preferable to save the output on disk, or
send it to the line printer. SIX12 contains a facility for doing
this, which is controlled by the following operators:
LPTOPEN Opens a file named SIX12.LPT on logical device SIX12:
if it exists, or if it does not, on logical device
LPT:. It does not initiate output to the file.
(Normally, by assigning the logical name LPT: to some
other device in advance, the user can cause the output
to go anywhere. However, this is frequently
inconvenient, since all output destined for the LPT:
will go to that device. Forgetting to deassign the
logical device produces unexpected results from other
programs. Therefore, logical device SIX12: is used
if it is assigned, since it is very unlikely such a
device name will conflict with any other program.)
LPTON Sets the output switch for output to the file. All
subsequent printout from SIX12 (except error messages)
will be directed to the file, not printed on the
terminal. This will be indicated by a "-" which
prints to the left of the prompt character.
&lptopen
&foo
34412 == foo
&lpton
-&foo
-&lptoff
&
LPTOFF Resets the output switch for output to the terminal.
It does not close the file, so that more file output
may be done later in the same file.
LPTDUP Sets the output switch for output to both terminal and
file simultaneously. This allows the user to obtain a
- 36 -
LINE PRINTER AND DISK I/O Page 12-2
transcript of the terminal session, particularly
useful when long debug printouts are made. However,
this applies only to output generated by SIX12.
Output generated by a routine called from SIX12 will
go wherever that routine puts it. Since output is
coming to the terminal, the "-" printed with the
prompt in LPTON mode is not printed.
LPTCLOSE Closes the file opened by LPTOPEN. All file output
between one pair of LPTOPEN and LPTCLOSE forms a
single file, no matter how many LPTONs and LPTOFFs
have intervened.
An automatic LPTOFF is executed at every break. Thus output will
normally go to the terminal during user interaction. LPT I/O on
TOPS-10 uses logical channel 17 (octal). Do not use LPT I/O when your
program is using channel 17 (octal).
An option is provided for saving the state of SIX12 on a disk file,
and restoring it at a later debugging session without having to do
considerable type-in, or save the whole core image.
SAVE 'filespec' saves all presently defined macros, requests for
monitoring, and routine actions (including conditions)
in a disk file specified by filespec, which is input
as a string and must be enclosed by single quotes.
The default extension is ".612".
LOAD 'filespec' deletes any existing macros, monitoring requests, or
routine actions, then loads the information in the
SAVE-written file named by filespec. The default
extension is ".612". A null extension may be obtained
by specifying only the "." in the filespec.
- SAVE and LOAD on TOPS-10 use logical channel 16 (octal). You
can use them in a program using that channel just as long as
you do not issue them when your program has something open on
16 (octal).
- The monitor and routine-actions tables contain absolute
memory addresses. Thus SAVE/LOAD should not be used to
preserve monitors or routine actions across a program relink.
Use STORE/RECALL for this.
- Since all previously existing macros are deleted by LOAD,
text space is compacted. The correct way to recover from a
'No space for macro text' error is to delete any unneeded
macros, then
&SAVE 'TEMP'
&LOAD 'TEMP'
- 37 -
LINE PRINTER AND DISK I/O Page 12-3
- The device specified (default "DSK:") must be capable of
supporting 36-bit binary I/O.
In order to save the state across a link, or to have a file of "stored
commands" available, the commands STORE and RECALL are available.
They are exactly like SAVE and LOAD, except the file is an ASCII text
file and thus may be edited or altered by the user. RECALL does not
clear the SIX12 state before it is executed, so a user may RECALL
several sets of commands in sequence.
The default extension, as in SAVE/LOAD, is ".612". Likewise, the I/O
on TOPS-10 is done using channel 16 (octal). The output device must
support ASCII data mode. Thus, it is possible to see all of the SIX12
state in a single command, by typing:
&STO 'TTY:'
The file may contain line numbers, and if it does they will be
stripped off. If an error occurs, the offending input line will be
printed, the error message will be issued, and input will terminate.
- 38 -
CHAPTER 13
DISPLAY
SIX12 has facilities for printing some information in a more
meaningful format than could be obtained from dot or slash. In
particular, special operators are available for displaying the
run-time stack, the symbol table, and SIX12's internal tables.
13.1 DISPLAYING ROUTINE-CALL STACK
These operators display the run-time stack in terms of routine calls.
CALLS displays the complete stack of routine calls. Each
call is displayed in the format
routine from calling-loc
Actuals: values
The first line (i.e., the current routine) is prefixed
with "B:" (for Before) if execution is stopped at the
routine's entry, or "A:" (for After), if at its exit,
as in
A:IMHERE from CALLER+17
Actuals: 1: 5 2: 0
CALLER from MAIN.F+12
Actuals: 1: 45
which indicates that we are at the exit of 'IMHERE'.
This display also prints out what handlers are enabled
for each routine, and whether or not a signal is being
processed. The condition handling features are
described in chapter 14.
LCALLS displays the call stack plus the locals area for each
routine (including saved registers)-- this may not be
very useful to a user not familiar with the Bliss
runtime environment. Locals are displayed after the
call to the routine which owns them. In particular,
Bliss-36 "local" declarations do not necessarily
- 39 -
DISPLAY Page 13-2
allocate the variable onto the stack.
CALL n displays the most-recent calls on the stack. If n is
omitted (i.e., CALL is used as a nullary operator),
only the last call (to the present routine) is
printed.
LCALL n works like CALL but also displays locals.
13.2 SYMBOL-TABLE SEARCHING
These operators are included for searching the symbol table.
PRS symbollist For each symbol given, PRS prints every entry in the
symbol table, in the format
name%ordinal value type module contents
For instance,
&PRS CTYPE,CX
CTYPE%1 400360 Own MAIN.. Routine
CTYPE%2_* 5601 Own INPU.. 0
CX%1 500040 Global DECL.. Routine w/debug
&
&PRS MAIN..
MAIN.. 400010 \Module 211 symbols
A * next to a name (following the ordinal) means that
that entry will not be used for typeout by SIX12 or
DDT (i.e., $K has been performed on it by DDT). A "\"
next to the word "Module" indicates this module is the
default module selected by the QUALIFY command. A "^"
to the left of the name indicates the name appears in
the high segment symbol table (if there are two symbol
tables; see section 17.4). If the value is a valid
memory location, and contains what looks like a DEBUG.
UUO or the first instruction of a routine entry
sequence, then the phrase "Routine w/debug" or
"routine" will be printed out. Otherwise, the octal
contents of the location will be printed.
PRM module-list This operator takes either no operands or a vector of
module names. The null operand case will cause the
names of all the modules to be listed, along with the
location where each is loaded and the number of
symbols in each module. If a list of module names is
given, it will list each module and the symbols within
it. A "^" to the left of the name indicates the name
- 40 -
DISPLAY Page 13-3
was found in the high segment symbol table (see
section 17.4).
&prm
SIX12 400123 Module 653 symbols
USERA 500666 Module 111 symbols
...
&prm xback
XBACK 454115 Module 4 symbols
P.AAA 454115 Own XBACK 251653325130
P.AAB 454117 Own XBACK 251653325130
XPO$BA 454121 Global XBACK Routine
SEARCH 'partially-specified-symbol'
This allows searches using the "wild-card" convention
that question-mark means any character, as in
&SEARCH 'P?C?'
PICK 500050 Own TABL.. Routine
PACE 3001 Global INPU.. 17,,INPU.O+27
&SEARCH '??????'
(prints every entry in symbol table)
The partially-specified symbol (only one per search)
must be entered in single quotes. SEARCH does not
print ordinals (the %-qualification). A "^" to the
left of the name indicates the symbol was found in the
high segment symbol table.
WHERE expression
Takes an expression or vector of expressions and
prints out the module and symbol which are closest to
the expression values.
&WHERE 410317,.foo
410317: Module thud, XYZ+117
410113: Module AB.., C+2
&
HELP Prints out a list of all the operators. PRINT OPER
can be used to make inquiries about specific
operators.
13.3 EXAMINING THE STATE OF SIX12
The PRINT operation displays the state of SIX12.
PRINT OPER name
PRINT OPER "char"
- 41 -
DISPLAY Page 13-4
displays the definition (priority and routine name for
each defined parse) of the specified operator, as in
PRINT OPER AND
PRINT OPER "_^"
Note: Priorities are displayed in decimal.
If SIX12 has suppressed its internal symbols (see
SIXLSF in section 17.2), the routine name printed for
default operators will be incorrect.
PRINT MACRO name
prints the text of the macro named 'name'. For
instance,
PRINT MACRO CALLR
If the macro name is omitted, all macro names and text
are displayed.
PRINT ACTION actionname routine
prints the status of the specified action on the
specified routine. The action must be given as one of
BREAK ABREAK OPAQ OPAQAFT TRACE TRACEAFT OK ALL
(remember that TRACE FROM = TRACE + TRACE AFTER). The
"OK" action will indicate the (always unconditional)
temporary breakpoint set on a routine from which an OK
has been done. If the routine name is omitted, the
actions for all routines are printed. The possible
responses are
1. Action not set
2. Unconditional
3. the text of the condition test
For example,
&PRINT BREAK OPAQ XYZ
Action not set
&PRINT ACTION ABREAK PPP
.X LSS 3
PRINT WATCH
PRINT MONITOR Prints the locations being monitored and the current
recorded "old value" stored in each.
&PRINT MONITOR
- 42 -
DISPLAY Page 13-5
M- FOO = 4407 == TEST.O+23
W- BAZ<18,18> = -773465 == 777777,,4313
&
NOTE
The byte pointer position and size values are
printed in decimal. The initial flag, "M-" or
"W-", indicates whether or not the location is
being monitored by a MONITOR or WATCH command.
PRINT MONITOR and PRINT WATCH are identical
commands.
In addition, the STORE operator can be used to print
the entire set of conditionals, breakpoints, monitors,
etc. on the user's terminal by doing
&STO 'tty:'
13.4 WRITING YOUR OWN PARAMETER DISPLAY
The default SIX12 parameter display is very simple, and not entirely
satisfactory for all applications. It is possible to write your own
parameter display routine and value display routine by setting the
symbol SIXHDR to contain the name of some user-defined routine. This
routine is called with the following parameters:
(address, name, parmptr, nparms, kind)
where the parameters are defined as:
address The address of the routine just called or returned
from.
name The name of the routine just called or returned from,
in SIXBIT.
parmptr At a routine entry (see kind, below), the address of
the first actual parameter to the routine; the second
actual is at this address +1, etc. At a routine exit,
this is the pointer to the value returned, and the
number of parameters is given as 1.
nparms The number of actual parameters to the routine.
kind A value of 1 if this is a routine entry, a value of 0
if this is a routine exit. Other values, such as for
displays of locals, may eventually be supplied, so a
simple true/false test should not be used to
- 43 -
DISPLAY Page 13-6
distinguish the two cases.
The user must return a value to indicate if the user has handled the
printing of the parameter list, or if SIX12 should. A true value
returned by the user handler indicates that the user has actually
processed the routines; a false value indicates that the default
SIX12 display should be used.
The user can use the output routine SIXOCH, which takes a parameter of
the single character to be written, and outputs it to the desired
devices; thus, if LPTON or LPTDUP modes are set, output will be
diverted to or copied to the transaction file.
The user may also call the routine SIXDPY, which takes a single
parameter, which is an address to be printed symbolically.This is
printed (via SIXOCH) on the output device(s). This routine may be
called whenever the user wishes the default SIX12 display for some
parameter.
The user may use the entry point SIXXEQ to execute any SIX12 command,
but in particular may pass in the string representing a routine name
(as a qualified name with a module name, or with a %-suffix). The
value of SIXXEQ is the value of the expression passed in, so in
particular the address of the routine will be returned. This may be
used for comparison with the address passed to the user routine
specified in SIXHDR. The intent of this is to allow the user to read
in a text file of routine names and printout requests and be able to
relate the external string name to the internal address when SIXHDR is
called.
Important Note
The string passed to SIXXEQ must be
terminated with a delete- code, 177
(octal)!!!
- 44 -
CHAPTER 14
CONDITION HANDLING
There are several aspects of condition handling brought about by
SIX12.
- The user should be able to invoke any of the functionality of
the condition handler mechanism from within SIX12.
- The condition handler should not interfere with the user's
interaction with SIX12.
- SIX12 should be able to monitor what the condition handler is
doing.
The user may wish to invoke the condition handler functions in a
variety of ways for a variety of reasons. Typical scenarios might be:
- The user, at a breakpoint or other point at which SIX12 has
control, wishes to raise a signal, most likely with the
intent of terminating the current execution path.
- The user has set a breakpoint at a condition handler routine
and wishes to take an action different than what the routine
would do, e.g., to resignal when the routine would resume,
unwind when the routine would resignal, etc.
- The user wishes to return to a previous level of SIX12 in
order to resume debugging in that context.
These are all supported in the current implementation of condition
handling in SIX12.
The condition handling mechanism may be invoked from SIX12 by the
following commands:
SIGNAL expression
This operator takes a single value, the value to be
signalled, and raises that signal. The value returned
is the value returned in the mechanism vector by the
conditional handler which was invoked. No additional
- 45 -
CONDITION HANDLING Page 14-2
parameters may be passed to the handler. If an Unwind
operation is performed, control returns to the handler
for the Unwind, and will not return to SIX12.
UNWIND This operation is valid only if SIX12 is in control
while a signal is being handled. It invokes the
SETUNWIND() operation. When control leaves SIX12, the
Unwind will begin (i.e., via GO, RETURN, etc.).
RESIGNAL expression
This operator is valid only if SIX12 has control at a
condition handler routine, e.g., by a BREAK, ABREAK,
or single-step operation which puts SIX12 in control
at the handler routine. If no operand is given, the
current signal is resignalled; thus, it is simply the
equivalent of the SIX12 command RETURN 0. If an
operand is given, this operand becomes the new signal
value in the signal vector.
RESUME expression
This operator is valid only if SIX12 has control at
the condition handler routine (see RESIGNAL, above).
If no operand is given, this is simply the equivalent
of the SIX12 command RETURN 1. If an operand is
given, this operand becomes the value returned to the
SIGNAL call.
BACKTO expression
This operator is valid whenever a recursive call on
SIX12 has been made. It invokes a special signal,
SIXUNW, which tells SIX12 to unwind back to a previous
level, given as the only operand.
5:&backto 2
2:&
If the user program is set up to call SIX12 on an
error, this provides a way of returning to the
previous incarnation of SIX12. An attempt to go back
to a non-existent level is an error; an attempt to go
back to the current level is a null operation.
POP expression This is the same function as BACKTO, except the
operand is the number of levels to return, rather than
the index of the level to return to. If no operand is
given, "1" is assumed. At level 5, the following two
commands will both return to level 2:
5:&BACKTO 2
2:&
....
5:&POP 3
2:&
- 46 -
CONDITION HANDLING Page 14-3
Whenever SIX12 is entered, it establishes a condition handler to trap
all signals which may be raised by calls which may be made to the user
program. The action of this handler is to print out the message that
the signal has been intercepted, then call SIX12 recursively to allow
the user to examine the state. When a RETURN or GO is issued, this
handler resignals.
A SIGNAL issued from SIX12 is also first intercepted by this handler.
Conspicuous by its absence is SIGNAL_STOP; this is because resumption
of a SIX12 signal would only return to SIX12, which is harmless,
whereas a resumption of a SIGNAL_STOP is probably an error, but the
user almost certainly does not want to exit to the monitor, but to
return to SIX12!
In addition, SIX12 establishes a default condition handler in SIX12
initialization, so that any signal not caught anywhere else, or
resignalled indefinitely, is ultimately caught by this outermost
handler. It issues a message indicating that the outermost SIX12
handler has been called, and then enters SIX12 command mode. An
attempt to RESIGNAL out of this handler will give control to the
default Bliss-36 condition handler, which issues an error message and
exits to the monitor. An attempt to set UNWIND and resume execution
will terminate the program, since this handler is established before
calling the main routine of the user program. What the user should do
here is to print the call stack, discover which, if any, handlers are
invoked, and set breakpoints where appropriate. A GO to this
outermost handler indicates a resumption is desired. If the signal
was raised by a SIGNAL_STOP, then the normal Bliss-36 SIGNAL_STOP
mechanism will terminate the program upon exit from SIX12.
Special checks are made in the various routines which print out the
call stack, e.g., the CALL, CALLS, LCALL, and LCALLS commands, as well
as printout at breakpoints. These checks will print out the handlers
which are established for routines, indicate when a SIGNAL is being
handled or an unwind is in progress, and print out the parameters to
the handler routines in a more useful format than the normal parameter
printout.
In the example below, the routine BH is an active handler routine for
some outer routine.
<=>At BH from FOO+26
Signalv at 4416 =[1]: 22
Mechanismv at 4424 =[1]: 4407
Enablev at 4430 =[3] 3347 XYZ+22 FOO
&CALLS
B: BH from FOO+26
Signalv at 4416 =[1]: 22
Mechanismv at 4424 =[1]: 4407
Enablev at 4430 =[3] 3347 XYZ+22 FOO
*** SIGNAL(22) ***
FOO from BAZ+7
Actuals: 1: .STACK+214,,GORP<0,#36>
...
- 47 -
CHAPTER 15
APR ERROR RECOVERY
It is frequently the case that users write debugging aid routines
which they can call from SIX12. Sometimes these are invoked by
extended SIX12 operators, which can be defined as in chapter 18, and
sometimes they are done as routine calls to be made from SIX12 command
level.
In any case, when debugging it is particularly annoying to call one of
these routines, and for one of several reasons take an APR trap (such
as an illegal memory reference trap). Getting back to the level of
SIX12 from which the call was made is extremely difficult, and
typically is not worth the effort.
The reasons such a call might fail are
1. The routine which has been called does not work.
2. The routine works, but the data passed is incorrect and the
routine is not robust enough to cope with this.
3. The routine works, but an incorrect value or address has been
passed because the user mis-typed it.
Recovery from this state is possible by using the BACKTO or POP
commands described in chapter 14. Consider the following example:
&foo/
34567
&PrintIt(345667)
?
?Ill mem ref at user pc 405162
.
In this example, the user (or perhaps, the user's keyboard) typed an
extra 6 in the address. To recover, and return to SIX12, proceed as
follows:
.DDT
SIXDDT$G
2:&pop
&
- 48 -
CHAPTER 16
MISCELLANEOUS OPERATORS
QUALIFY name Sets the default module name for symbols which are
qualified with the null module name (see section 4.3).
A symbol is qualified with a null module name when
only the "\" character appears, with no module name
before it.
BASE n Sets the default base to be n, and prints the new base
in decimal. Subsequent input numbers are assumed to
be in this base, and output will appear in this base
(except for items specified to appear in the alternate
base, either decimal or octal by means of the #
operator). If n is omitted BASE prints the current
base. The initial default BASE is 8 (for octal). The
special case of BASE 0 resets the base to the initial
base (octal), no matter what it was set to.
WBASE n Sets the maximum displacement to be allowed when
printing symbolic addresses in the form
'symbol+offset'. If "n" is omitted, WBASE prints the
current offset value using the current default base.
base. The WBASE is initialized to 1000 (octal).
SETTRACE Turns on the trace flag. When execution resumes
tracing will begin immediately. This cancels the
effects of any active OPAQUE. The GOTRACE operator
described earlier is equivalent to
SETTRACE ; GO
CLRTRACE Turns off the trace flag. This cancels the effects of
an active TRACE AFTER or a previous SETTRACE. The
GOCLR operator described earlier is equivalent to
CLRTRACE; GO
- 49 -
MISCELLANEOUS OPERATORS Page 16-2
NODEBUG This performs
&.JB41 = #255000000000
&GO
Note:#255000000000 (octal) is a JFCL 0,0
Thus, the DEBUG. UUO is rendered a no-op. This can
be used to improve execution time if you are only
running a program without intending to debug it. In
addition, should you reenter SIX12 after this, the
prompt will include a notation that you are in NODEBUG
mode.
DEBUG This undoes the modification of the UUO intercept
location by establishing the linkage instruction to
SIX12. Unlike the NODEBUG operator, this does not do
a GO. This is useful if you have at some point done a
NODEBUG and now have entered SIX12 (either through DDT
or an error call) and wish to turn debugging back on.
RESET Performs a RESET (UUO or JSYS). All currently opened
files are closed, and various appropriate resetting of
the job state is done by the monitor. Note that
neither SIX12 nor the program are reset or restarted
by this command.
IDENT Prints out the version of SIX12, the runtime
environment it expects (TOPS-10 or TOPS-20), and the
linkage conventions in effect.
For example:
&IDENT
SIX36 V8-6 (TOPS-20 I/O) for Bliss-36
Using default linkage with registers (decimal)
Stack pointer: 15
Frame pointer: 13
Value register: 1
Preserved registers: 14,12,11,10,9,8,7,6,0
Non-preserved registers: 5,4,3,2
! An exclamation point at the start of a line indicates
a comment and the remainder of the line is ignored.
- 50 -
CHAPTER 17
USING SIX12
17.1 GENERAL USAGE
The modules to be debugged must be compiled as follows:
- Each module to be debugged must be compiled with the DEBUG
switch set. This can be accomplished by including DEBUG in
the module head, or by specifying "/DEBUG" in the compiler
command string. It is not necessary that all modules in a
program be compiled with DEBUG. However, if the main module
is not compiled with the DEBUG switch, SIX12 will not be
properly initialized, and there is the possibility of getting
the message:
?Halt at user pc n
where the instruction at user pc n is a DEBUG. UUO. If this
is the case, call one of the initialization routines SIX10,
SIX36C or SIX36 as described in Appendix A.
- Should you come up in "old SIX12", (typically V6.24), it is
likely that your MAIN module was compiled with an old version
of Bliss-36. If so, it contains a .REQUEST of SIX12.REL.
The new SIX12 is included in the BLISS OTS library. You can
force loading of the new SIX12 by explicitly loading the
module SIX36 from the appropriate OTS file.
Once you have compiled all your files, link them with the appropriate
version of SIX12 and DDT; be sure that local symbols are loaded for
your program files. There are several version of SIX12, depending on
the version of Bliss being used, the linkage conventions, and the
underlying operating system. The Bliss-36 compiler will include a
.REQUEST linker directive to obtain the appropriate version.
------------------------------
[1] On TOPS-20, DDT can be implicitly merged at execution time. See
Chapter 8, Concerning DDT.
- 51 -
USING SIX12 Page 17-2
17.2 LINK-TIME OPTIONS
Using either the TOPS-10 or TOPS-20 linker, options may be selected at
link time for SIX12 switches SIXSTA (STARTFLG), SIXENB (ENABFLG) and
SIXNPL (NOPOLLFLG). The LINK switch /DEFINE: can be used to define
initial values for these switches:
Location LINK name Default value Complement
-------- --------- ------------- ----------
SIXSTA SIXSTF -1 /DEFINE:SIXSTF:0
SIXENB SIXENF -1 /DEFINE:SIXENF:0
SIXNPL SIXPOL 0 /DEFINE:SIXPOL:-1
SIXLSF -1 /DEFINE:SIXLSF:0
The values which have runtime locations assigned may also be set at
execution time using DDT or SIX12 itself; for example, SIXSTA
(STARTFLG) may be defined false (/DEFINE:SIXSTF:0) but set true before
execution begins by using DDT. Such redefinition will cause the
linker to issue a "multiply defined symbol" warning when the
definition in the SIX12 module is encountered, but this message should
be ignored.
The symbol SIXLSF determines if SIX12 will delete its local symbols at
startup. Ordinarily, SIX12 deletes all of its local symbols except
STARTFLG (SIXSTA), ENABFLG (SIXENB) and NOPOLLFLG (SIXNPL). Setting
SIXLSF to 0 at link time will suppress this automatic deletion, and is
normally only done when a SIX12 maintainer is working on SIX12. If
the SIX12 local symbols are left in, they frequently cause "Ambiguous
symbol" errors because they conflict with user-defined symbols. When
the symbols are deleted, the SIX12 symbol table is compacted.
Although this saves no space (the space saved is not reclaimed or
reused in any way), it saves time because symbol table search is
linear, and SIX12 defines nearly 600 deletable symbols.
17.3 TOPS-10 USAGE
The easy way to load SIX12 is with the monitor DEBUG command:
.DEBUG your program files,REL:SIXB12
If you prefer to use LINK directly, you can issue
.R LINK
*/DEBUG your program files,REL:SIXB12
*/GO
If space is at a premium, you can save about 1200 words by loading
SIX12 without its local symbols, as in
.DEBUG your program files,REL:SIXB12%"NOLOCALS"
(All global symbols in SIX12 begin with the letters S I X.) SIX12
- 52 -
USING SIX12 Page 17-3
normally purges all of the SIX12 local symbols from the symbol table
(except for STARTFLG, ENABFLG and NOPOLLFLG). This saves time and
prevents "Ambiguous symbol" error messages.
17.4 SIX12 AND OVERLAYS
SIX12 does not work particularly well with overlay systems based on
the overlay handler supported by LINK. However, there are some
modifications which have been made to allow those programs which have
user-built overlay systems using either the GETSEG UUO on TOPS-10 or
the GET JSYS on TOPS-20 to interact more gracefully with SIX12. The
/SEGMENT switch to the Linker can be used to force the code into the
correct segment.
In order to simplify some of the discussion below, the term "low
segment" when applied to TOPS-20 will refer to the resident pages, and
"high segment" to the set of pages which are swapped in for each
overlay. If the addresses of the overlay segments are not greater
than the addresses of the resident segment, SIX12 will probably not
work correctly.
In order to work at all with an overlay system, SIX12 must be loaded
in the low segment so that it is always at the same address. Each
overlaid high segment must have its own symbol table, and they all
must overlay with the same offset (e.g., if one segment is loaded at
location 600000 , all the segments must be loaded at 600000 ). The
symbol table for the common code must be in the low segment (this
symbol table can contain symbols for one of the overlaid high segments
as well); the symbol tables for each of the overlaid high segments
must be in the respective high segments (except for one which is
typically the first segment used, which may be shared with the symbol
table for the resident segment). The Linker /SYMSEG switch can be
used to force the symbol table into the correct segment.
The high segment symbol table is found (typically) by looking at the
location .JBHSM relative to the high segment offset .JBHGH. However,
in TOPS-20 systems, if the high segment is relocated with the /SET
switch the value of .JBHGH is not changed (this happens correctly in
TOPS-10 systems), and the value .HIGH. must be used. Consequently,
there is a complex rule for searching symbol tables.
- If the symbol .HIGH. is defined, and is different from
.JBHGH, it is used as the start of the high segment;
otherwise .JBHGH is used.
- If the value stored in .JBHSM from the start of the high
segment is the same as the value stored in .JBSYM, there is
only one symbol table and it is searched.
- If the value stored in .JBHSM from the start of the high
segment is different from the value stored in .JBSYM, there
are two symbol tables. In this case:
- 53 -
USING SIX12 Page 17-4
* The high segment symbol table is searched first.
* If the symbol is not found in the high segment table, the
low segment symbol table is searched. Note that this may
occasionally produce strange results if the low segment
table contains symbols from the initial segment.
* Ambiguous symbols whose ambiguity arises because they are
defined uniquely in the high segment symbol table but
have a duplicate (and different) definition in the low
segment table will not be treated as ambiguous; the high
segment definition is considered the correct one. If the
ambiguity arises exclusively in the high segment symbol
table, the symbols are treated as ambiguous.
The address of the high segment symbol table is recomputed after each
entry into SIX12 and after each call to a user routine or invocation
of a user-defined operator, since any of these conditions could change
the high segment symbol table. If the high segment disappears, SIX12
will continue to work correctly providing the common symbol table
defined in .JBSYM is in the low segment.
These rules appear complex, but seem to provide reasonable behavior
when overlay systems are used. The correct rules may actually be more
complex.
17.5 SIX12 AND USER UUO HANDLERS
The debugging linkages generated by the DEBUG switch use the 037
(octal) user UUO. If your program does not use user UUOs (opcodes 001
(octal)-037 (octal)), you can skip the following. If you do use UUOs,
you must
- Not use opcode 037 (octal),
- Arrange for your UUO handler to link to SIX12 properly. This
is merely a matter of getting the proper jump address for
SIX12's UUO entry point. This is available as the global
symbol SIXUUO.You may also retrieve the jump address from
location .JB41 before loading it with a branch to your own
handler. (SIX12 loads .JB41 with a PUSHJ to itself
immediately after stack initialization.) Your UUO
initialization code would look something like:
Global
UUOROUTS : VECTOR[ %O'40' ];
External Routine
UUOSwitch
External
%Name('.JB41');
.
- 54 -
USING SIX12 Page 17-5
.
UUOROUTS[%O'037'] = .%Name(.JB41)<0,18>;
! Put PUSHJ SREG,UUOSWITCH into loc. 41
!
%Name('.JB41') = %O'260'^27 or 15<0,0>^23 or UUOSwitch<0,0>;
where the routine UUOSwitch
Machop JRST = %O'254';
Global Routine UUOswitch =
JRST(0,UUOROUTS[ %Name('.JB41') ],0,1);
must be in a module which is compiled without DEBUG switches.
- 55 -
CHAPTER 18
DEFINING YOUR OWN OPERATORS
CAVEAT Programmer
This code was not thoroughly tested,
after it was converted to Bliss-36.
As previously advertised, SIX12 is capable of easy extension. The
method for this is normally to define new operators or revise standard
ones to suit your needs. (Please review what we said about operators
under 'SIX12 expressions', if it is not fresh in your mind.)
18.1 WHAT DEFINES AN OPERATOR
The syntax (print name, priority, possible parses) of an operator is
defined by an entry in a syntax analyzer table. Its semantics are
defined by a routine which the table entry points to. To evaluate the
operator, the analyzer calls this routine using a standard linkage
convention. The content of this section is a description of 1) the
linkage convention and 2) the proper method for making entries in the
syntax table.
Linkage: Since operands and values can be vectors, it is not possible
to transfer them by standard Bliss linkage. Instead, variables are
set to point to an operand and give its length. The variables are:
SIXLP Contains a pointer to the first word of the left
operand. (Undefined if no left operand.)
SIXLC Contains the number of words in the left operand.
(Zero if no left operand.)
SIXRP Like SIXLP, except points to corresponding values for
the right operand.
SIXRC Contains the number of words in the right operand.
- 56 -
DEFINING YOUR OWN OPERATORS Page 18-2
(Zero if no right operand).
These variables are set at the routine call; the routine may destroy
them if it wishes. (The contents of the operands may also be
destroyed.) To return a value, the routine should set these two
variables before returning:
SIXVP Must contain the address of the first word of the
value. (The left half of SIXVP is ignored.)
SIXVC Must contain the number of words in the value.
If no value is to be returned these can be left unmodified. (The
criterion for finding a value is that SIXVC be positive; it is set to
zero before calling the routine.) Note that operands and values are
always vectors of fullwords.
An evaluating routine may need to determine what parse it has been
called under. The parse in use can always be determined by examining
SIXLC and SIXRC, but a more convenient way is provided. Evaluating
routines are called with a single parameter (standard Bliss linkage),
which has the value
0 for null parse (no operands)
1 for prefix parse (a right operand only)
2 for postfix parse (a left operand only)
3 for infix parse (both operands);
thus bit 0 denotes the presence of a right operand and bit 1 that of a
left operand. We suggest examining the source of SIX12 to see the
best ways to code operators. The macro Apply and the routines XBASE
and LPAREN are particularly good objects of study.
For each operator symbol, the table of operators contains the symbol
itself (print name), and information on each of the four possible
parses for the symbol. This information consists of the priority of
operation and the address of the evaluating routine for that parse.
(If both are zero, the parse does not apply.) Priorities are in
increasing sequence, that is an operator of priority 15 is evaluated
before one of priority 14. If the user is making a permanent
modification to SIX12, he should modify the table in the source
program; this is explained by notes in the source. Otherwise, in
order to avoid recompiling SIX12, the user can create his new routines
separately, compile them, link them together with SIX12 and the
program to be debugged, and modify the operator table at run-time. To
facilitate this approach, the linkage variables explained above are
all global names, and both an operator and a global routine are
provided for modifying the table at run-time.
- 57 -
DEFINING YOUR OWN OPERATORS Page 18-3
18.1.1 Important Restriction
The routine which is called to execute the operator, and any routines
it calls to do its work, must not have debug linkages!!! This is very
important! If any routine is called during the processing of a SIX12
operator which itself contains debug linkages, the contents of
locations SIXLP, SIXLC, SIXRP and SIXRC will be destroyed. In cases
where it is not possible to call service routines which have not been
compiled with debug linkages, or the possibility of debug linkages is
suspected, then the parameters must be copied to local storage and
never again referred to via the locations in SIX12. The routine
actually called to execute the operator must never be compiled with
debug linkages, since the debug call will destroy SIXLP, SIXLC, SIXRP
and SIXRC before the operator routine even gets to see them!
18.2 DEFINING OPERATORS FROM SIX12
The DEFINE command allows you to add new operators at SIX12
command-prompt level. These definitions would typically be kept as
commands in an ascii file and incorporated using a RECALL command.
DEFINE name,parse = priority,routine
DEFINE "char",parse = priority,routine
sets the parse information as requested. "Parse" can
be one of keywords
NULL PREFIX POSTFIX INFIX
or a literal in the range 0..3. Note that only the
specified parse is affected; the others remain set as
before. (If a new operator symbol is being defined,
the other 3 are initialized to zero, i.e. "parse not
applicable".) For example,
DEFINE SIXBIT,PREFIX = 100,CONVRT
where CONVRT names a routine to translate ASCII inputs
to SIXBIT outputs, could be used to implement the
SIXBIT stringtype. Once this has been entered, the
user could issue
& FILNAM = SIXBIT 'ABCDEF'
Again,
DEFINE "?",0 = 10,DISPLAY
would make it possible to call the routine DISPLAY by
typing a question mark. (If no value were required
from "?" and DISPLAY expected no arguments, this could
be done even if DISPLAY had not been written
explicitly as a SIX12 operator...) Thus
- 58 -
DEFINING YOUR OWN OPERATORS Page 18-4
& ?
(output from DISPLAY)
&
The PRINT OPER operation can be used to verify the
effects of DEFINE. Remember that priorities are
printed in decimal by PRINT OPER.
Certain characters are illegal as single-character
user-defined operators; see page 9.
18.3 DEFINING OPERATORS FROM A USER PROGRAM
Many applications programs would like to have SIX12 operators defined,
but do not wish to require users to always define them at the SIX12
command level (even using the RECALL command). Therefore, the global
entry point is available to user programs. The user program may call
SIXOP during initialization to enter new operators in the table. The
general form of the SIXOP call is:
SIXOP(name,parse,priority,routine)
where
name is either a SIXBIT name for the operator, left
justified in a word, or a single ASCII 7-bit character
in the left halfword. (e.g., (%C'~'^18) in Bliss-36,
to define the operator ~).
parse is 0, 1, 2 or 3 for null, prefix, postfix or infix
parse, as described in section 18.
priority is the priority of the operator; see the SIX12 source
for determining the exact priority (however, most
prefix commands like BREAK have priority 20 and most
nullary commands have priority 50).
routine is the address of a routine to call for the operator.
An example is to define a command BP which prints its arguments out as
byte pointers:
SIXOP(%sixbit 'BP',1,50,outbp);
- 59 -
DEFINING YOUR OWN OPERATORS Page 18-5
where routine "outbp" is defined as
Global Routine OutBP(ptype):NoValue=
begin
! Implements the BP n,n,n,... command
! The parse type code (ptype) is ignored,
! since only prefix parse is recognized
! this routine will fail if "outoct" or "write" contain debug
! linkages or call any routines with debug linkages
external SIXRP: ref vector;
external SIXRC;
incr i from 0 to .SIXRC-1 do
begin
outoct(.SIXRP[.i]<0,18>);
write("<");
outdec(.SIXRP[.i]<30,6>);
write(",");
outdec(.SIXRP[.i]<24,6>);
write(">");
end;
end;
An example of a routine which returns a value is given below. It is
important to note that the user is responsible for finding space to
store the result pointed to by SIXVP. There are many ways of doing
this, but the simplest is to allocate an own variable and put its
address into SIXVP. The extent of the variable must be greater than
that of the routine stack frame so a local variable will not work.
For simple values, a single word can be allocated; for vector values,
a multiple word value must be allocated. The Bliss-36 routine below
allocates a 20-word vector, and assumes that no call will pass in more
characters than will fit; if necessary, a bounds check could be put
in, but that would unnecessarily complicate this example. In any
case, SIX12 will copy the result out before it calls any other
routine. Thus the variable is both serially reusable and
"re-entrant".
This routine implements the SIXBIT operator described above. The
"cvsix" call converts a single character from ASCII to SIXBIT.
- 60 -
DEFINING YOUR OWN OPERATORS Page 18-6
global routine CONVRT:NoValue=
begin
! converts ASCII value to SIXBIT
! SIXRC is the count of the number of words in the ASCII string
! SIXRP points to the words
! SIXVC will contain the number of words of SIXBIT
! SIXVP will contain the addresses of each of the words
!
! we cannot convert a SIXBIT operand longer than 20
! words (100 characters)
own SIXBITVALUE: Vector[20];
local OutPtr, InPtr, InCnt;
external SIXRC;
external SIXRP: ref VECTOR;
InCnt = .SIXRC * 5; ! 5 chars/word
OutPtr = ch$ptr(SIXBITVALUE);
InPtr = ch$ptr(SIXRP[0]);
decr i from .InCnt to 0 do
ch$wchar_a(cvsix(ch$rchar_a(InPtr)),OutPtr);
SIXVC = ch$allocation(ch$diff(OutPtr,ch$ptr(SIXBITVALUE)));
SIXVP = SIXBITVALUE
end;
- 61 -
APPENDIX A
GLOBAL ENTRY POINTS, VALUES AND DATA AREAS
Symbol Description
SIX10 Initialization entry used for Bliss-10.
SIX12 User callable entry point to explicitly invoke SIX12;
called with one parameter.
SIX36C Initialization entry used for Bliss-36.
SIX36 Initialization entry used for Bliss-36 with extended
addressing PDP-10s; currently unused.
SIXDDT Jump address to start SIX12 from DDT using SIXDDT$G.
A valid stack pointer (register SIXSP) must be set up
first, if necessary. If SIX12 has not been
initialized, then use PUSHJ SIXSP,SIXxxx$X instead,
where SIXxxx is SIX10, SIX36 or SIX36C. GO from
SIX12 will return to DDT.
SIXDPY A routine of one parameter; when called, it prints
out the name+offset of the address passed as the
parameter. This is useful when the user wishes to
write other routines (such as APR trap routines)
which would like to be able to print out a symbolic
address.
SIXENB Global symbol for ENABFLG, which controls console
polling.
SIXENF Initial value of SIXENB (ENABFLG). May be redefined
using LINK.
SIXHDR Normally 0, can be set to the address of a user
routine which is a handler for printing out the
parameters to a routine. Thus, non-standard linkages
or formatted printout can be done.
SIXNPL Global name of NOPOLLFLG, which permanently disables
console polling.
SIXOCH Routine entry point to print a single character on
the selected output devices (e.g., LPT when LPTON
mode is selected, LPT and TTY when LPTDUP mode is
selected). Takes a single parameter, the character
to be printed.
SIXOSA Routine entry point to print an ASCIZ string on the
terminal using the SIX12 internal routine for this
purpose. Called with one parameter, the address of
the beginning of the string. If the address is not
- 62 -
GLOBAL ENTRY POINTS, VALUES AND DATA AREAS Page A-2
valid, nothing is printed and the value of this
routine is 0; if the address is valid, the value is
1.
SIXOP User-callable entry point for defining new SIX12
operators.
SIXPAT Twenty word patch area. BIND may be used to
establish symbolic names for variables the user sets
in this area, e.g.
&BIND CHECKIT = SIXPAT[4]
&if |.CHECKIT| BREAK someroutine
&CHECKIT = 1
SIXPOL Initial value of SIXNPL (NOPOLLFLG). May be
redefined using LINK.
SIXRET Instruction to return to SIX12 using SIXRET$X. This
is equivalent to JRST @.JBOPC$X or $P.
SIXSP Stack register name (suppressed for typeout).
SIXSTA Global name for STARTFLG. Controls automatic entry
to SIX12 at startup.
SIXSTF Initial value of SIXSTA(STARTFLG). May be redefined
using LINK.
SIXSTK Contains the value of the stack pointer register when
SIX12 is initialized.
SIXUNW The low-order 18 bits are used as the value of the
unwind signal for the BACKTO command.The user must
write code so that only the low-order 18 bits are
examined when comparing this value. The user must
never do a SETUNWIND() call and then resignal this
signal, or SIX12 will become terriblly confused.
This value is currently 7170 (octal). It is
recognized that this could conflict with some signal
value established by the user. Thus, the Linker can
be used as described in section 17.2 to change the
value of this signal:
/DEFINE:SIXUNW:12345
would change the value to 12345. Of course, this
will cause a multiply-defined-symbol warning from the
linker.
SIXUUO Address of SIX12 handler for DEBUG. UUO.
SIXXEQ A routine of one parameter, a pointer to a string
terminated with a DEL code (177 (octal)). The string
is evaluated as a SIX12 command, and the value
returned, if any, becomes the value of SIXXEQ. If
there is any error, if the string pointer is not a
valid address, or if the string pointer is 0, the
value returned is 0.
- 63 -
APPENDIX B
BUILDING A SIX12
This chapter tells how to compile a version of SIX12 from source files
(such as a release tape).
The file SIX12.B36 should be compiled as follows to obtain particular
variations:
Variation Command Line to Build
--------- ---------------------
TOPS-10, B10 Linkages BLISS SIX12/VARIANT:10/TOPS10
TOPS-10, B36 Linkages BLISS SIX12/TOPS10
TOPS-20, B36 Linkages BLISS SIX12/TOPS20
The module SIX36 must then be replaced in the appropriate OTS file
using MAKLIB. The differences between the OTS files are discribed in
the following table.
OTS File Usage
--------- ----------------------------
B361AB.REL Tops-10, KA-10, B36 Linkages
B361AT.REL Tops-10, KA-10, B10 Linkages
B361LB.REL Tops-10, KL-10, B36 Linkages
B361LT.REL Tops-10, KL-10, B10 Linkages
B362LB.REL Tops-20, KL-10, B36 Linkages
B362PB.REL Tops-20, KL-10, B36 Linkages, Extended Addressing
Restriction
The Bliss10 linkage conventions will not
work correctly in a JSYS environment.
- 64 -
BUILDING A SIX12 Page B-2
B.1 UNUSUAL REGISTER ALLOCATIONS
It is sometimes the case that in order to interface to an existing
system, a Bliss-36 system must adopt conventions other than the
standard conventions. Usually this affects the stack pointer and
value return register allocations, but other effects are possible.
SIX12 provides much of this configuration ability. In addition to
selecting which features of the running system are selected (for
example, TOPS-10 or TOPS-20 I/O), the register set, basic linking
conventions, and other information about the execution environment may
be tailored by use of these files.
Examine the source for SIX12.B36 to see how the LINKAGE_REGS are
established. Great care must be taken to prevent SIX12 from
"trashing" your program. In particular, look at the routines UUOH and
CALLEM.
- 65 -
APPENDIX C
ERROR MESSAGES
Unknown symbol
Description: The name could not be found in the DDT symbol
table or the SIX12 operator-table (when qualified
with %0).
User Action: Either the symbol is misspelled or symbols aren't
loaded.
Illegal character
Description: The indicated character is not a valid constituent
for any command or symbol.
User Action: Correct the command line.
Syntax error
Description: An invalid command or non-numeric characters in a
digit string or a malformed symbol-name.
User Action: Correct the command line.
Incorrect number of arguments
Description: A field-reference was not of the form "base<p,s>";
or a structure reference was made with other than
1 (for a VECTOR) or 3 (for a BLOCK) parameter(s);
or the DEFINE command has an incorrect number of
operands; or the PRINT command has the wrong
number of operands.
User Action: Correct the command line.
Unmatched brace
Description: A mismatch in the number (or placement) of "( )"
or "< >" pairs.
- 66 -
ERROR MESSAGES Page C-2
User Action: Correct the expression.
Base must be from 2 to 10 decimal
Description: The BASE operator only supports radix 2 thru radix
10.
User Action: Use a valid radix value in the BASE command
<name>: No debug linkage found for this routine
Description: A DEBUG. UUO ( opcode 037 octal ) was not found
for the mentioned routine.
User Action: Recompile the module with /DEBUG.
Invalid equals
Description: The "=" operator has been misused.
User Action: Correct the command line.
ACTION type must be one of: BREAK, ABREAK, OPAQ, OPAQAF, TRACE,
TRACEA or ALL
Description: A PRINT ACTION command has not indicated which
action(s) should be displayed.
User Action: Correct the command.
Improper file-spec
Description: The quoted-string provided as a file-spec could
not be parsed according to the host operating
system rules.
User Action: Correct the file-spec.
Open failure
Description: A file could not be opened. On TOPS-20, this is
followed by the text for the last JSYS error.
User Action: Determine why the file couldn't be opened.
Transmission error
Description: An i/o error has occurred in writing some file
produced by the SAVE or STORE command. On
TOPS-10, the output file is deleted. Or, an i/o
error occurred in reading some file with the LOAD
or RECALL command.
User Action: Determine why the file couldn't be accessed.
- 67 -
ERROR MESSAGES Page C-3
No space for macro text
Description: There is no more room for defining macros.
User Action: See the discussion of LOAD and SAVE in Chapter 12.
If the message persists after compressing
macro-text, you can recompile SIX12 after
increasing the value of the literal NMACROS.
No space for macro name definition
Description: The file used to LOAD from contains too many macro
definitions.
User Action: Use the FORGET command to remove macros from
SIX12. If this fails, recompile SIX12 after
increasing the value of the literal NMACROS.
Name already defined
Description: The macro you are declaring already exists.
User Action: Change the name or use FORGET to delete the old
definition.
No space for symbol definition
Description: Either there is no patch-space (module "PAT.."
isn't in the DDT symbol table) or the patch space
is full.
User Action: Make more patch-space available.
Digit invalid for base
Description: The value being processed contained digits which
are invalid in the current radix.
User Action: Enter the number in the current radix, or change
the radix.
Actual/Local index out of range
Description: The index of a non-existant local or
actual-parameter was specified.
User Action: An LCALLS command will display the actuals and
locals to show what the valid range for the index
is.
:<field-ref>: invalid field reference (byte pointer)
Description: The specified byte-pointer for a fetch, store,
WATCH or MONITOR command had a non-zero indirect
or index field, or a bad value for position or
- 68 -
ERROR MESSAGES Page C-4
size.
User Action: Correct the expression.
Line printer file not open
Description: The LPTON or LPTDUP command was issued without
issuing a LPTOPEN.
User Action: Issue a LPTOPEN command.
Line printer file still open
Description: A RESET command is illegal when the LPT file is
still open.
User Action: Issue a LPTCLOSE command to close the output file.
DDT not loaded
Description: This message will occur when the DDT command is
given to SIX12 and DDT is not present. On
TOPS-10, this usually means that .JBDDT does not
point to the DDT entrypoint.
User Action: On TOPS-10, relink with DDT. On TOPS-20, ^C and
enter DDT with the DDT command.
Multiple definitions in DDT symbol table for <name>
Description: SIX12 is unable to resolve which of several
symbols should be used.
User Action: Use the PRS command to determine which symbol you
are interested in. Then use %-qualification or
module-qualification to access the symbol.
OK works only at routine entry
Description: The OK command can only be issued from a
BREAK-point (routine-entry). It is meaningless at
an ABREAK-point (routine-exit).
User Action: Type GO instead.
Ambiguous command name
Description: Not enough characters were supplied to determine
which SIX12 operator is being referenced.
User Action: Type more characters of the operator.
Valid only when in signal handler routine
Description: UNWIND, RESUME or RESIGNAL commands cannot be
- 69 -
ERROR MESSAGES Page C-5
issued unless you are presently inside a condition
handler.
User Action: Don't do these commands when you aren't at a BREAK
or ABREAK for the handler.
<address>: Ill Mem Ref
Description: The specified address is non-existant. (TOPS-10)
User Action: Correct the expression.
<address>: Refers to non-existent page
Description: The specified address is non-existant. (TOPS-20)
User Action: Correct the expression.
Already at top SIX12 level
Description: Attempt to do a POP or BACKTO command when already
at the outermost invocation of SIX12.
User Action: None.
You are already above level <number>
Description: A BACKTO <number> command was given when SIX12 was
already above the level specified.
User Action: Correct the command.
Which Parse?
Description: The DEFINE command didn't correctly specify which
parse (NULL, PREFIX, POSTFIX or INFIX) was being
defined.
User Action: Correct the command.
<address>: Memory Write Protected
Description: An assignment expression failed because of memory
protection.
User Action: Correct the assignment expression destination.
<address>: Memory Read Protected
Description: The specified address cannot be accessed.
(Execute only).
User Action: Correct the expression being used to access
memory.
- 70 -
ERROR MESSAGES Page C-6
Warning: You are in NODEBUG mode
Description: A reminder that if you were to enter a "GO"
command that SIX12 will not gain control at any
SIX12-breakpoints.
User Action: If you want to re-enter "DEBUG" mode, issue the
DEBUG command.
Operation makes no sense in NODEBUG mode
Description: The command just issued won't have any effect as
long as NODEBUG is active.
User Action: Issue the DEBUG command to re-enter debug-mode and
re-issue the command which caused this message.
Module is in different high segment
Description: The specified module qualification refers to a
module name which is inaccessible; or, the
nullary QUALIFY command couldn't print out the
name of the default qualification module.
User Action: Correct the expression.
Could not find SS$UNW in symbol table
Description: The BACKTO and POP commands cannot be used unless
this symbol is defined, indicating that
condition-handling support is linked in. This
should never occur unless the DDT symbol table has
been corrupted or has not been loaded in the
image.
User Action: Something is wrong with the DDT symbol-table.
Determine the problem and correct it.
- 71 -
Page Index-1
INDEX
#
change input radix . . . . . . . 3-2
%
%0 six12 symbol-table . . . . . 4-5
%a . . . . . . . . . . . . . . . 4-4
%l . . . . . . . . . . . . . . . 4-4
%n . . . . . . . . . . . . . . . 4-5
actual parameters, accessing . . 4-4
disambiguate identifiers . . . . 4-5
local variables, accessing . . . 4-4
( )
compound expression . . . . . . 4-1
routine call . . . . . . . . . . 4-1
() . . . . . . . . . . . . . . . . 4-1
(halt at user pc)
tops-10 . . . . . . . . . . . . 2-1
(illegal instruction)
tops-20 . . . . . . . . . . . . 2-1
* . . . . . . . . . . . . . . . . 4-1
+ . . . . . . . . . . . . . . . . 4-1
- . . . . . . . . . . . . . . . . 4-1
.
fetch operator . . . . . . . . . 4-2
/
DDT examine . . . . . . . . . . 4-1, 5-1
infix divide . . . . . . . . . . 4-1
<line-feed> . . . . . . . . . . . 7-3
<p,s>
byte pointers . . . . . . . . . 4-2
= . . . . . . . . . . . . . . . . 4-2
?
escape convention . . . . . . . 4-4
[ ] . . . . . . . . . . . . . . . 4-2
^ . . . . . . . . . . . . . . . . 4-1
|
conditional text delimiter . . . 6-4
macro text delimiter . . . . . . 11-1
ABREAK
stop after execution . . . . . . 6-2
AND . . . . . . . . . . . . . . . 4-1
APR trap recovery . . . . . . . . 15-1
ATRACE . . . . . . . . . . . . . . 6-3
BACKTO . . . . . . . . . . . . . . 14-2
BASE . . . . . . . . . . . . . . . 3-2, 16-1
BIND . . . . . . . . . . . . . . . 11-1
BLOCK structure . . . . . . . . . 4-3
BLOCKVECTOR structure . . . . . . 4-3
BREAK
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Page Index-2
at routine-entry . . . . . . . . 6-2
CALLS . . . . . . . . . . . . . . 13-1
CLRTRACE . . . . . . . . . . . . . 16-1
COPAQUE . . . . . . . . . . . . . 6-3
DABREAK
delete after-breaks . . . . . . 6-2
DBREAK
delete entry breaks . . . . . . 6-2
DEBUG . . . . . . . . . . . . . . 16-2
DEFINE . . . . . . . . . . . . . . 18-3
DISABLE
suppress input monitoring . . . 9-1
DMONITOR . . . . . . . . . . . . . 10-1
DOPAQUE . . . . . . . . . . . . . 6-3
DOPAQUE AFTER . . . . . . . . . . 6-3
DTRACE . . . . . . . . . . . . . . 6-3
DTRACE AFTER . . . . . . . . . . . 6-3
DTRACE FROM . . . . . . . . . . . 6-3
DWATCH . . . . . . . . . . . . . . 10-1
EQL . . . . . . . . . . . . . . . 4-1
FORGET . . . . . . . . . . . . . . 11-1
GEQ . . . . . . . . . . . . . . . 4-1
GO . . . . . . . . . . . . . . . . 7-2
GOCLR . . . . . . . . . . . . . . 7-2
GOTRACE . . . . . . . . . . . . . 7-2
GTR . . . . . . . . . . . . . . . 4-1
HELP . . . . . . . . . . . . . . . 13-3
IDENT . . . . . . . . . . . . . . 16-2
Ill mem ref
re-entering SIX12 . . . . . . . 15-1
Illegal operators . . . . . . . . 3-4
LCALLS . . . . . . . . . . . . . . 13-1
LEQ . . . . . . . . . . . . . . . 4-1
Linker options . . . . . . . . . . 17-2
LOAD . . . . . . . . . . . . . . . 12-2
LPTCLOSE . . . . . . . . . . . . . 12-2
LPTDUP . . . . . . . . . . . . . . 12-1
LPTOFF . . . . . . . . . . . . . . 12-1
LPTON . . . . . . . . . . . . . . 12-1
LPTOPEN . . . . . . . . . . . . . 12-1
LSS . . . . . . . . . . . . . . . 4-1
MACRO . . . . . . . . . . . . . . 11-1
Macro
recovering memory . . . . . . . 12-2
MONITOR . . . . . . . . . . . . . 10-1
Monitoring
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Page Index-3
input . . . . . . . . . . . . . 9-1
variables . . . . . . . . . . . 10-1
Name qualification . . . . . . . . 4-6
Names, syntax . . . . . . . . . . 4-4
NEQ . . . . . . . . . . . . . . . 4-1
NOCOPAQUE . . . . . . . . . . . . 6-4
NODEBUG . . . . . . . . . . . . . 16-2
NOT . . . . . . . . . . . . . . . 4-1
OK . . . . . . . . . . . . . . . . 7-3
OPAQUE . . . . . . . . . . . . . . 6-3
OPAQUE AFTER . . . . . . . . . . . 6-3
Operator, illegal . . . . . . . . 3-4
OR . . . . . . . . . . . . . . . . 4-1
POLLOFF
terminate input monitoring . . . 9-1
POLLON
restore input monitoring . . . . 9-1
POP . . . . . . . . . . . . . . . 14-2
PRINT ACTION . . . . . . . . . . . 13-4
PRINT MACRO . . . . . . . . . . . 13-4
PRINT MONITOR . . . . . . . . . . 13-4
PRINT OPER . . . . . . . . . . . . 13-3
PRINT WATCH . . . . . . . . . . . 13-4
PRM
print modules . . . . . . . . . 13-2
PRS
print symbols . . . . . . . . . 13-2
QUALIFY
name qualification . . . . . . . 16-1
Quoted strings . . . . . . . . . . 3-2
Radix of numbers . . . . . . . . . 3-2
RECALL . . . . . . . . . . . . . . 12-3
REF-structure . . . . . . . . . . 4-3
RESET . . . . . . . . . . . . . . 16-2
RESIGNAL . . . . . . . . . . . . . 14-2
RESUME . . . . . . . . . . . . . . 14-2
RETURN . . . . . . . . . . . . . . 7-2
Routine calls . . . . . . . . . . 4-1
SAVE . . . . . . . . . . . . . . . 12-2
SEARCH . . . . . . . . . . . . . . 13-3
SETTRACE . . . . . . . . . . . . . 16-1
Shift . . . . . . . . . . . . . . 4-1
SIGNAL . . . . . . . . . . . . . . 14-1
SIXREF . . . . . . . . . . . . . . 4-3
STEP . . . . . . . . . . . . . . . 7-3
STORE . . . . . . . . . . . . . . 12-3
Structure access . . . . . . . . . 4-3
Structure BLOCK . . . . . . . . . 4-3
Structure VECTOR . . . . . . . . . 4-3
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Page Index-4
Structure, REF- . . . . . . . . . 4-3
TRACE . . . . . . . . . . . . . . 6-2
TRACE FROM . . . . . . . . . . . . 6-3
UNWIND . . . . . . . . . . . . . . 14-2
User-enhancement
defining operators . . . . . . . 18-1
SIXDPY . . . . . . . . . . . . . 13-6
SIXOCH . . . . . . . . . . . . . 13-6
SIXXEQ . . . . . . . . . . . . . 13-6
User-enhancements
parameter display . . . . . . . 13-5
return-value display . . . . . . 13-5
VECTOR structure . . . . . . . . . 4-3
Vector structure . . . . . . . . . 4-3
WATCH . . . . . . . . . . . . . . 10-1
Watching variables
see monitoring
WBASE . . . . . . . . . . . . . . 16-1
WHERE . . . . . . . . . . . . . . 13-3
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