[petsc-users] Still reachable memory in valgrind

[Matthew Knepley]

On Tue, Oct 12, 2021 at 10:16 AM Pierre Seize <pierre.seize at onera.fr> wrote:

> Sorry, I should have tried this before:
>
> I checked out to v3.14, and now both malloc and PetscMalloc1 are
> reported as definitely lost, so I would say it's a bug.
>

I am not sure what would be the bug. This is correctly reporting that you
did not free the memory.

  Thanks,

    Matt


> Pierre
>
>
> On 12/10/21 15:58, Pierre Seize wrote:
> > Hello petsc-users
> >
> > I am using Valgrind with my PETSc application, and I noticed something:
> >
> >  1 #include <petscsys.h>
> >  2
> >  3 int main(int argc, char **argv){
> >  4   PetscErrorCode ierr = 0;
> >  5
> >  6   ierr = PetscInitialize(&argc, &argv, NULL, ""); if (ierr) return
> > ierr;
> >  7   PetscReal *foo;
> >  8   malloc(sizeof(PetscReal));
> >  9   ierr = PetscMalloc1(1, &foo); CHKERRQ(ierr);
> > 10   ierr = PetscFinalize();
> > 11   return ierr;
> > 12 }
> >
> > With this example, with today's release branch, I've got this Valgrind
> > result (--leak-check=full --show-leak-kinds=all):
> >
> > ==2036== Memcheck, a memory error detector
> > ==2036== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
> > ==2036== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright
> > info
> > ==2036== Command: ./build/bin/yanss data/box.yaml
> > ==2036==
> > ==2036==
> > ==2036== HEAP SUMMARY:
> > ==2036==     in use at exit: 1,746 bytes in 4 blocks
> > ==2036==   total heap usage: 2,172 allocs, 2,168 frees, 9,624,690
> > bytes allocated
> > ==2036==
> > ==2036== 8 bytes in 1 blocks are definitely lost in loss record 1 of 4
> > ==2036==    at 0x4C29BE3: malloc (vg_replace_malloc.c:299)
> > ==2036==    by 0x41A4FD: main (main.c:8)
> > ==2036==
> > ==2036== 32 bytes in 1 blocks are still reachable in loss record 2 of 4
> > ==2036==    at 0x4C2B975: calloc (vg_replace_malloc.c:711)
> > ==2036==    by 0xACF461F: _dlerror_run (in /usr/lib64/libdl-2.17.so)
> > ==2036==    by 0xACF4127: dlsym (in /usr/lib64/libdl-2.17.so)
> > ==2036==    by 0x56ECBB5: PetscInitialize_Common (pinit.c:785)
> > ==2036==    by 0x56EF325: PetscInitialize (pinit.c:1203)
> > ==2036==    by 0x41A4E2: main (main.c:6)
> > ==2036==
> > ==2036== 70 bytes in 1 blocks are still reachable in loss record 3 of 4
> > ==2036==    at 0x4C29BE3: malloc (vg_replace_malloc.c:299)
> > ==2036==    by 0x400F0D0: _dl_signal_error (in /usr/lib64/ld-2.17.so)
> > ==2036==    by 0x400F26D: _dl_signal_cerror (in /usr/lib64/ld-2.17.so)
> > ==2036==    by 0x400A4BC: _dl_lookup_symbol_x (in /usr/lib64/ld-2.17.so)
> > ==2036==    by 0x83B9F02: do_sym (in /usr/lib64/libc-2.17.so)
> > ==2036==    by 0xACF40D3: dlsym_doit (in /usr/lib64/libdl-2.17.so)
> > ==2036==    by 0x400F2D3: _dl_catch_error (in /usr/lib64/ld-2.17.so)
> > ==2036==    by 0xACF45BC: _dlerror_run (in /usr/lib64/libdl-2.17.so)
> > ==2036==    by 0xACF4127: dlsym (in /usr/lib64/libdl-2.17.so)
> > ==2036==    by 0x56ECBB5: PetscInitialize_Common (pinit.c:785)
> > ==2036==    by 0x56EF325: PetscInitialize (pinit.c:1203)
> > ==2036==    by 0x41A4E2: main (main.c:6)
> > ==2036==
> > ==2036== 1,636 bytes in 1 blocks are still reachable in loss record 4
> > of 4
> > ==2036==    at 0x4C2BE2D: memalign (vg_replace_malloc.c:858)
> > ==2036==    by 0x54AC0CB: PetscMallocAlign (mal.c:54)
> > ==2036==    by 0x54AFBA9: PetscTrMallocDefault (mtr.c:183)
> > ==2036==    by 0x54ADDD2: PetscMallocA (mal.c:423)
> > ==2036==    by 0x41A52F: main (main.c:9)
> > ==2036==
> > ==2036== LEAK SUMMARY:
> > ==2036==    definitely lost: 8 bytes in 1 blocks
> > ==2036==    indirectly lost: 0 bytes in 0 blocks
> > ==2036==      possibly lost: 0 bytes in 0 blocks
> > ==2036==    still reachable: 1,738 bytes in 3 blocks
> > ==2036==         suppressed: 0 bytes in 0 blocks
> > ==2036==
> > ==2036== For counts of detected and suppressed errors, rerun with: -v
> > ==2036== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
> >
> >
> > The first report is the malloc on line 8, fine.
> > The second and the third correspond to still reachable memory from
> > PetscInitialize on line 6, I often got these so I usually discard it.
> > The fourth and last is the one that worries me : the memory from
> > PetscMalloc1 on line 9 is reported as "still reachable", but I don't
> > think it should.
> > Is there something I do not understand, or is this a bug ?
> >
> > Thanks in advance,
> >
> > Pierre
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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