Re: [Valgrind-users] Application runs correctly in Valgrind but segfaults otherwise

[Christoffer H. <Chr...@nu...>]

Dynamic memory, it points to an array inside a struct allocated with
normal calloc()

tis 2010-08-10 klockan 09:14 +0200 skrev Bart Van Assche:
> On Mon, Aug 9, 2010 at 4:01 PM, Christoffer Haglund
> <Chr...@nu...> wrote:
> 
>         That's interesting. This what Memcheck tells me about the
>         application that crashes:
>         
>         $ valgrind --leak-check=full --show-reachable=yes
>         --track-origins=yes ./unittest_t9write -r api -o api.xml
>         ==19513== Memcheck, a memory error detector
>         ==19513== Copyright (C) 2002-2009, and GNU GPL'd, by Julian
>         Seward et al.
>         ==19513== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun
>         with -h for copyright info
>         ==19513== Command: ./unittest_t9write -r api -o api.xml
>         ==19513== 
>         
>         This is t9write unit test runner, compiled with: -Wall -Wextra
>         -ansi -pedantic -O3 
>         
>         No errors.
>         
>         ==19513== 
>         ==19513== HEAP SUMMARY:
>         ==19513==     in use at exit: 0 bytes in 0 blocks
>         ==19513==   total heap usage: 1,050,205 allocs, 1,050,205
>         frees, 268,688,656 bytes allocated
>         ==19513== 
>         ==19513== All heap blocks were freed -- no leaks are possible
>         ==19513== 
>         ==19513== For counts of detected and suppressed errors, rerun
>         with: -v
>         ==19513== ERROR SUMMARY: 0 errors from 0 contexts (suppressed:
>         4 from 4)
>         
>         
>         So Memcheck does not find any overwrites, but that's likely
>         the problem anyway; using GDB I can see that the segfault
>         occurs inside a loop that's basically a memset:
>         
>             for ( ; n > 0; n-- )
>                 *intPtr++ = value;
>         
>         Now, I haven't checked out exactly what instructions are
>         generated, and I probably won't unless anyone finds this
>         interesting or think it looks like a Memcheck bug :-)
>         
> 
> 
> Does intPtr point to an array or to dynamically allocated memory ?
> 
> Bart.


  // Christoffer
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CHRISTOFFER HAGLUND
Software Developer, Decuma

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