Does Open MPI v5.0 support RHEL 6 gcc 4.4.7?

[jsquyres]

In doing some random testing over the weekend, I noticed that the gcc 4.4.7 that ships with RHEL 6 does not compile OpenPMIX and also does not compile PRTE on Open MPI master HEAD.

I do note that if I compile PMIX and PRTE independently (with a modern gcc), and then configure Open MPI with --with-pmix=PATH_TO_PMIX --with-prte=PATH_TO_PRTE, Open MPI "compiles" and links.

I put "compiles" in quotes because there are a bunch of warnings about thread functions in nearly every file that is compiled.

Is it time to drop support for gcc 4.4.7 in Open MPI? If so, it should be documented.

[rhc54]

PMIx ad PRRTE build and run just fine with gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), which is as far back as I have gone. If you want it to go back further, then you'll need to provide a patch.

[jsquyres]

I don't want to provide a patch. 😄

Just to be clear: the gcc 4.8.5 that @rhc54 cites is the default compiler in RHEL 7. The gcc 4.4.7 that I cited is the default for RHEL 6.

It may well be ok to say "we don't support gcc 4.4.7". If so, we just need to document it.

[bwbarrett]

RHEL6 is EOL, but still in extended support. From AWS's point of view, we don't have a good way to test it, so supporting it would be difficult.

[awlauria]

Extended support of RHEL6 goes through June 30th, 2024 it looks like.

[jsquyres]

Question from @gpaulsen:

Also don’t we require C11 support for building v5.0?
https://gcc.gnu.org/wiki/C11Status If so, we might want the minimum to be gcc v4.9 ?

(I don't know/remember where that previous discussion ended up, so I'm including the question here)

[jsquyres]

We talked about this on the RM call today, and will bring it up again tomorrow on the community call.

RM reaction is basically: "No, we don't really want to support gcc 4.4.7 any more... unless someone needs it." Meaning: unless someone supplies fixes for PRTE, PMIX, and potentially Open MPI, we're going to not support gcc 4.4.7 in Open MPI 5.0.0.

Specifically, @jsquyres volunteers to make a configure test that will fail if a too-old gcc is used.

@rhc54 notes that we should probably port the configure test to PRTE and PMIX, too.

[jsquyres]

To close this issue, the answer is: no.

#9398 puts in a configure error on master, and #9478 ports that fix to the v5.0.x branch. Fixes also went in on the OpenPMIx and PRTE repos, too.