* gcc-2.95 OK, gcc-{3,4}.X not OK
@ 2010-01-01 5:44 Andris Kalnozols
2010-01-01 11:48 ` Andrew Haley
0 siblings, 1 reply; 2+ messages in thread
From: Andris Kalnozols @ 2010-01-01 5:44 UTC (permalink / raw)
To: gcc
I've got a bit of a quandry here and would like the advice
of people who are more experienced than I am at C programming
and debugging.
We've got a legacy application that compiles and runs fine
using the following compilers/platforms:
HP-UX 11.23 (PA-RISC) ANSI-C and aC++ C.11.23.04
HP-UX 11.31 (ia64) HP C/aC++ B3910B A.06.23 [May 18, 2009]
Debian "squeeze" i686 gcc-2.95
Here is some debugging output during a runtime parse
of the application's custom scripting language after
compiling with gcc-2.95:
'encountered _endif_; leaving gen_if()
'*cmd->cmd' is '134523664'
' cmd->op' is '200'
' flags' is '0'
' pc' is '200'
'tokenbuf' is 'endif'
' pcptr ' is '155572084'
'*pcptr ' is '0'
' pcptr->code' is '155572068'
'*pcptr->code' is '200'
' pc' is '155572068'
'*pc' is '200'
' pcptr->code->op' is '200'
calling '[while]parse_cmd' in parse_body
in parse_cmd():
'tokenbuf [before tokenize()]' is 'end'
'tokenbuf [after tokenize()]' is 'end'
Database ready 20:53:08
The problem is that gcc-3.X and gcc-4.X compilers generate
code (no matter the optimization level) that fails at
runtime like this:
'encountered _endif_; leaving gen_if()
'*cmd->cmd' is '134523035'
' cmd->op' is '200'
' flags' is '0'
' pc' is '200'
'tokenbuf' is 'endif'
' pcptr ' is '160593780'
'*pcptr ' is '0'
' pcptr->code' is '0'
Segmentation fault
If the bug was a basic programming error, one would expect a
runtime failure (dereferencing a NULL pointer) no matter which
compiler was used. The application compiles cleanly with no
warnings using "-Wall". Were there any transition issues with
the newer gcc compilers of which I may not be aware?
Thanks,
Andris
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: gcc-2.95 OK, gcc-{3,4}.X not OK
2010-01-01 5:44 gcc-2.95 OK, gcc-{3,4}.X not OK Andris Kalnozols
@ 2010-01-01 11:48 ` Andrew Haley
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Haley @ 2010-01-01 11:48 UTC (permalink / raw)
To: Andris Kalnozols; +Cc: gcc
[redir to gcc-help]
On 01/01/2010 05:44 AM, Andris Kalnozols wrote:
> If the bug was a basic programming error, one would expect a
> runtime failure (dereferencing a NULL pointer) no matter which
> compiler was used.
I would not expect that, and I have no idea whay you would. Undefined
behaviour can happen in any way: maybe the program appears to run
correctly, maybe it faults.
> The application compiles cleanly with no warnings using "-Wall".
> Were there any transition issues with the newer gcc compilers of
> which I may not be aware?
No. As you've done the obvious first stage (using -Wall) you now
should run your program under Valgrind, assuming that it is available
on your system.
Andrew.
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