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Re: gcc-4.3 optimizer bugs?



Neal Becker wrote:
Horst H. von Brand wrote:

Neal Becker <ndbecker2 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


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