MPI_Type_get_envelope_c is wrong

[lindsayad]

Thank you for taking the time to submit an issue!

Background information

What version of Open MPI are you using? (e.g., v4.1.6, v5.0.1, git branch name and hash, etc.)

331a547

Describe how Open MPI was installed (e.g., from a source/distribution tarball, from a git clone, from an operating system distribution package, etc.)

git clone

If you are building/installing from a git clone, please copy-n-paste the output from git submodule status.

 08e41ed5629b51832f5708181af6d89218c7a74e 3rd-party/openpmix (v1.1.3-4067-g08e41ed5)
 30cadc6746ebddd69ea42ca78b964398f782e4e3 3rd-party/prrte (psrvr-v2.0.0rc1-4839-g30cadc6746)
 6032f68dd9636b48977f59e986acc01a746593a6 3rd-party/pympistandard (remotes/origin/main-23-g6032f68)
 dfff67569fb72dbf8d73a1dcf74d091dad93f71b config/oac (dfff675)

Please describe the system on which you are running

Ubuntu 24.04.2 LTS

Architecture:             x86_64
  CPU op-mode(s):         32-bit, 64-bit
  Address sizes:          52 bits physical, 57 bits virtual
  Byte Order:             Little Endian
CPU(s):                   384
  On-line CPU(s) list:    0-383
Vendor ID:                AuthenticAMD
  Model name:             AMD EPYC 9654 96-Core Processor

---

Details of the problem

The problem is already outlined in the code comment. This code leaves 4 bytes of 8 byte integers uninitialized which leads to valgrind errors and broken code in our PETSc application, MOOSE

ompi/ompi/mpi/c/type_get_envelope_c.c

Lines 64 to 66 in 331a547

	/* TODO:BIGCOUNT: Need to embiggen ompi_datatype_get_args */
	rc = ompi_datatype_get_args( type, 0, (int *)num_integers, NULL, (int *)num_addresses, NULL,
	(int *)num_datatypes, NULL, combiner );

[bosilca]

Try this:

diff --git a/ompi/mpi/c/type_get_envelope_c.c b/ompi/mpi/c/type_get_envelope_c.c
index 24229e327c..999174776a 100644
--- a/ompi/mpi/c/type_get_envelope_c.c
+++ b/ompi/mpi/c/type_get_envelope_c.c
@@ -62,8 +62,13 @@ int MPI_Type_get_envelope_c(MPI_Datatype type,
    }
 
 /* TODO:BIGCOUNT: Need to embiggen ompi_datatype_get_args */
-   rc = ompi_datatype_get_args( type, 0, (int *)num_integers, NULL, (int *)num_addresses, NULL,
-                           (int *)num_datatypes, NULL, combiner );
+   int i_num_integers, i_num_addresses, i_num_datatypes;
+   rc = ompi_datatype_get_args( type, 0, &i_num_integers, NULL, &i_num_addresses, NULL,
+                           &i_num_datatypes, NULL, combiner );
+   *num_integers     = i_num_integers;
+   *num_addresses    = i_num_addresses;
+   *num_large_counts = 0;
+   *num_datatypes    = i_num_datatypes;
    OMPI_ERRHANDLER_NOHANDLE_RETURN( rc, rc, FUNC_NAME );
 }
 

[lindsayad]

Yep, that fixed our application!