oper@DHAFEU51.BITNET (08/06/87)
Hi netlanders,
sorry, if you have seen this before, but my first posting _seemed_ to
go wrong.
Devoloping a Pascal program, which consists of about 70 modules and which
uses Ingres database and SMG window-management functions, a mysterious error
appears. The program is written with the following system configuration:
VAX\VMS 4.5
Pascal compiler 3.5 using Compiler options: DEBUG/NOOPTIMIZE/LIST
Linker 4.0 using Linker options: MAP/DEBUG/BRIEF
Debugger 4.5.6
The error message looks like:
%SYSTEM-F-ACCVIO, access violation, reason mask=05, virtual address=7EFFFFA0,
PC=0001127C, PSL=03C00000
Improperly handled condition, image exit forced
Signal arguments Stack contents
Number = 00000005 6148000D
Name = 0000000C 70747075
00000005 72676F72
7EFFFFA0 056D6D61
0001127C 04000000
03C00000 6C000000
327FF26D
01000111
C6000000
007FF26C
Register dump
R0 = 00000000 R1 = 0001050D R2 = 00000000 R3 = 7FF26CFC
R4 = 00000000 R5 = 00000000 R6 = 7FF26CFC R7 = 7FFED78A
R8 = 7FFED052 R9 = 7FFED25A R10= 7FFEDDD4 R11= 7FFE33DC
AP = 7FF26CB1 FP = 7FF26C70 SP = 7FF26CED PC = 0001127C
PSL= 03C00000
The situation in the program according to the error is described in the
following figure:
----------------- ------------------------------------
| | | |
| | | |
| | | |
| while .. | | procedure abc; |
| : | | : |
| abc; | | smg$paste_virtual_display (..) |
| : | | : |
| end; (*while*)| | end; (*proc*) |
| end. | | end. |
----------------- ------------------------------------
Module A Module B
Module A calls procedure abc of module B inside a while-loop. During the
first call of procedure abc no error appears and the program works as expected.
During the second call of procedure abc, every statement included in its
body is executed as expected, except one run-time library window-management
procedure, the smg$paste_virtual_display function call. This statement isn't
executed, but the procedure abc can be finished without any error message.
After executing the last statement of procedure abc correctly and before
starting the next statement of module A, the error message shown above
appears.
It's not possible to detect the error using the VMS Debugger, because
setting a breakpoint near the end of procedure abc and stepping ahead lets
the error disappear! No error message is given and the program can be
continued. It needn't be emphasized, that every declaration of the
smg-functions and the use of the Linker is faultless and according to the
conventions.
We would like to know the following:
Who has any experience with errors, perhaps caused by the Linker or the
smg-window-management-functions or something else, which disappear if the
debbuger is used to step over the statements, which are supposed to cause
the error?
Who can give us any hint to the reason of the error?
thanks in advance
OPER@DHAFEU51.bitnet
FernUniversitaet Hagen
-Informatikrechner-"Philip_Young.XSISHQ"@XEROX.COM (08/06/87)
You write that > It's not possible to detect the error using the VMS Debugger, because > setting a breakpoint near the end of procedure abc and stepping > ahead lets the error disappear. I've had similar problems with both Pascal and PL/I related to code optimization. When you run under the debugger you see no problem since you must compile with /NOOPT. The same is true if you compile with /NOOPT/DEBUG and then $RUN/NODEBUG. Is this what is happening here? Phil Young Xerox Corp.