[OMPI devel] memory leak caused by possibly wrong initialization in ompi_ddt_duplicate()

[Andreas Schäfer]

Hi,

one of our projects recently exposed severe memory leakage when using
ROMIO to write a complex derived datatype (a struct made of other
structs) to a file. From our code we distilled the attached short
program to reproduce the leak.

After some Valgrind sessions, it appears as if the memcpy in
ompi_ddt_duplicate() is a bit overhasty, as it does copy the old
type's reference counter, too. 

I don't know if this is the right way to fix it, but if I apply the
patch below to ompi the leak is fixed.

Cheers!
-Andreas


diff -ru openmpi-1.1.1/ompi/datatype/dt_create_dup.c
openmpi-1.1.1-fixed/ompi/datatype/dt_create_dup.c
--- openmpi-1.1.1/ompi/datatype/dt_create_dup.c 2006-06-14
21:56:41.000000000 +0200
+++ openmpi-1.1.1-fixed/ompi/datatype/dt_create_dup.c   2006-11-13
00:35:03.000000000 +0100
@@ -33,6 +33,7 @@
     int32_t old_index = pdt->d_f_to_c_index;

     memcpy( pdt, oldType, sizeof(ompi_datatype_t) );
+    ((opal_object_t *)pdt)->obj_reference_count = 1;
     pdt->desc.desc = temp;
     pdt->flags &= (~DT_FLAG_PREDEFINED);
     /* ompi_ddt_create() creates a new f_to_c index that was saved



#include <mpi.h>

int main(int argc, char* argv[]) {
    MPI::Init();
    MPI::File file;
    char buf[1024];
    file = MPI::File::Open(MPI::COMM_WORLD,
            "/tmp/memleak", MPI_MODE_CREATE | MPI_MODE_WRONLY, MPI::INFO_NULL);

    // create a struct consisting of a derived datatype
    MPI::Aint displacementsAlpha[] = {0};
    MPI::Datatype memberTypesAlpha[] = {MPI::INT};
    int lengthsAlpha[] = {1};
    MPI::Datatype structAlpha = MPI::Datatype::Create_struct(1, lengthsAlpha, 
displacementsAlpha, memberTypesAlpha);
    structAlpha.Commit();

    MPI::Aint displacementsBravo[] = {0};
    MPI::Datatype memberTypesBravo[] = {structAlpha};
    int lengthsBravo[] = {1};
    MPI::Datatype structBravo = MPI::Datatype::Create_struct(1, lengthsBravo, 
displacementsBravo, memberTypesBravo);
    structBravo.Commit();

    // this will leak like hell
    for (;;) 
        file.Write(buf, 1, structBravo);

    file.Close();
    MPI::Finalize();
}

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