[fpc-pascal] ansistrings, exceptions, pascal call stack and access violations

[David Emerson]

Compiling sysutils with -gl gave the call stack seen below... insightful, I suppose, but not necessarily useful ;)

It definitely points to what Peter said about the ansistring finalize writing to the same place in the stack. Examining the stack, it seems that dump_stack calls get_caller_addr, and then I assume the access violation is about the address being unfindable since it's been overwritten.

1.9.5 (today's w32 binary) didn't work any better

re: Peter's last comment: so I guess the finalization of that temp ansistring is done at the end of play_with_strings, rather than being done within play_with_strings just after completion of the call to do_nothing_with_an_ansistring ... but it still irks me that the temp ansistring is created even if the function requiring it is not called. Oh well.

Has this been filed as a bug? (Is it considered a bug? I should hope so) ... for now, I guess I'm condemned to always be recompiling with a directive to either handle exceptions or see a call stack. I can live with that (as if I have a choice!)


Thanks, guys... keep up the good work, I'm sure this problem will be solved eventually :-)

~David.



Here's the stack with the debug version of sysutils (1.9.4):

An unhandled exception occurred at 0x004275D8 :
EDivByZero : Division by zero
  $004275D8  TEST_DIVISION_BY_ZERO,  line 13 of t.pas
  $702E7420 line 1 of windows.pp
An unhandled exception occurred at 0x00415B8F :
EAccessViolation : Access violation
  $00415B8F  GET_CALLER_ADDR,  line 1207 of e:/c/194/src/rtl/i386/i386.inc
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FDA0 line 1 of windows.pp
  $702E7420 line 1 of windows.pp
An unhandled exception occurred at 0x00415B8F :
EAccessViolation : Access violation
  $00415B8F  GET_CALLER_ADDR,  line 1207 of e:/c/194/src/rtl/i386/i386.inc
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FB2C line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FDA0 line 1 of windows.pp
  $702E7420 line 1 of windows.pp
An unhandled exception occurred at 0x00415B8F :
EAccessViolation : Access violation
  $00415B8F  GET_CALLER_ADDR,  line 1207 of e:/c/194/src/rtl/i386/i386.inc
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066F8B8 line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FB2C line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FDA0 line 1 of windows.pp
  $702E7420 line 1 of windows.pp
An unhandled exception occurred at 0x00415B8F :
EAccessViolation : Access violation
  $00415B8F  GET_CALLER_ADDR,  line 1207 of e:/c/194/src/rtl/i386/i386.inc
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066F644 line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066F8B8 line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FB2C line 1 of windows.pp
  $00420B58  DUMP_STACK,  line 779 of e:/c/194/src/rtl/inc/system.inc
  $0066FDA0 line 1 of windows.pp
  $702E7420 line 1 of windows.pp