Fix for Coverity CID 1357152.

Or at least that was the origin of the issue. It turns out
we were freeing the wrong buffer (but as it only happen in the
case of an error we never noticed).

ompi/mca/coll/base/coll_base_alltoall.c

@@ -45,7 +45,7 @@ mca_coll_base_alltoall_intra_basic_inplace(const void *rbuf, int rcount,
     int i, j, size, rank, err = MPI_SUCCESS, line;
     OPAL_PTRDIFF_TYPE ext, gap;
     ompi_request_t **preq, **reqs;
-    char *tmp_buffer;
+    char *allocated_buffer = NULL, *tmp_buffer;
     size_t max_size;
 
     /* Initialize. */
@@ -67,9 +67,9 @@ mca_coll_base_alltoall_intra_basic_inplace(const void *rbuf, int rcount,
     if( NULL == reqs ) { err = OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto error_hndl; }
 
     /* Allocate a temporary buffer */
-    tmp_buffer = calloc (max_size, 1);
-    if (NULL == tmp_buffer) { return OMPI_ERR_OUT_OF_RESOURCE; }
-    tmp_buffer -= gap;
+    allocated_buffer = calloc (max_size, 1);
+    if( NULL == allocated_buffer) { err = OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto error_hndl; }
+    tmp_buffer = allocated_buffer - gap;
     max_size = ext * rcount;
 
     /* in-place alltoall slow algorithm (but works) */
@@ -119,7 +119,8 @@ mca_coll_base_alltoall_intra_basic_inplace(const void *rbuf, int rcount,
 
  error_hndl:
     /* Free the temporary buffer */
-    free (tmp_buffer);
+    if( NULL != allocated_buffer )
+        free (allocated_buffer);
 
     if( MPI_SUCCESS != err ) {
         OPAL_OUTPUT((ompi_coll_base_framework.framework_output,