[petsc-users] Still reachable memory in valgrind

[Pierre Seize]

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