gcc-4.3 optimizer bugs?

[Neal Becker]

William Cohen wrote:

> Neal Becker wrote:
>> Horst H. von Brand wrote:
>> 
>>> Neal Becker <ndbecker2 at gmail.com> wrote:
>>>> We are trying to track down a numerical problem with unuran that occurs
>>>> on
>>>> gcc-4.3.  I know that gcc now has a very extensive test suite, and bugs
>>>> are
>>>> not common.  I'm just wondering, are others finding similar problems
>>>> with gcc-4.3?
>>>> We are working on preparing a bug report.  The symptoms are:
>>>> 1) Problem disappears if -O0
>>>> 2) Problem disappears if a printf is added
>>> That probably means there is a problem with the memory layout (something
>>> stomping on your variables?).
>> 
>> Even if valgrind is silent?
>> 
>> (BTW, this is not my code)
>> 
> 
> Valgrind is instrumenting the code at a very low level. As a result,
> valgrind doesn't have knowledge where one structure or array ends and
> another starts. Valgrind will catch access to uninitialized location in
> memory but is unlikely to catch array out of bound references.
> 
> Would it be possible to compile the code with the mudflap option in gcc.
> Mudflap is in the compiler and has a better understanding of the data
> structures:
> 
> http://gcc.gnu.org/wiki/Mudflap_Pointer_Debugging
> http://gcc.gnu.org/onlinedocs/gcc-4.2.3/gcc/Optimize-Options.html#index-fmudflap-502
> 
> 
> -Will
> 
Thanks for the tip about mudflap.

I tried:
MUDFLAP_OPTIONS=-viol-segv ./t_cstd

No segv.  Anything else I should try?