# 3.3. Compiler Notes

- PMIx requires a C99-capable compiler to build.

- PMIx requires a compiler that either supports C11 atomics or the GCC `__atomic` atomics (e.g., GCC >= v4.8.x).

- 32-bit platforms are not currently supported.

- In general, the latest versions of compilers of a given vendor’s series have the least bugs. We have seen cases where Vendor XYZ’s compiler version A.B fails to compile PMIx, but version A.C (where C>B) works just fine. If you run into a compile failure, you might want to double check that you have the latest bug fixes and patches for your compiler.

- PMIx does not support the PGI compiler suite on OS X or MacOS. See issues below for more details:

  - https://github.com/open-mpi/ompi/issues/2604

  - https://github.com/open-mpi/ompi/issues/2605

- At least some versions of the Intel 8.1 compiler seg fault while compiling certain PMIx source code files. As such, it is not supported.

- It has been reported that the Intel 9.1 and 10.0 compilers fail to compile PMIx on IA64 platforms. As of 12 Sep 2012, there is very little (if any) testing performed on IA64 platforms (with any compiler). Support is “best effort” for these platforms, but it is doubtful that any effort will be expended to fix the Intel 9.1 / 10.0 compiler issuers on this platform.

- Early versions of the Intel 12.1 Linux compiler suite on x86_64 seem to have a bug that prevents PMIx from working. Symptoms including immediate segv of the wrapper compiler (`pmixcc`) and PMIx-based applications. If you upgrade to the latest version of the Intel 12.1 Linux compiler suite, the problem will go away.

- The Portland Group compilers prior to version 7.0 require the `-Msignextend` compiler flag to extend the sign bit when converting from a shorter to longer integer. This is different than other compilers (such as GNU). When compiling PMIx with the Portland compiler suite, the following flags should be passed to PMIx’s `configure` script:

      shell$ ./configure CFLAGS=-Msignextend \
             --with-wrapper-cflags=-Msignextend ...

  This will both compile PMIx with the proper compile flags and also automatically add `-Msignextend` when the C wrapper compiler is used to compile user PMIx-based applications.

- It has been reported that Pathscale 5.0.5 and 6.0.527 compilers give an internal compiler error when trying to build PMIx.

- As of July 2017, the Pathscale compiler suite apparently has no further commercial support, and it does not look like there will be further releases. Any issues discovered regarding building / running PMIx with the Pathscale compiler suite therefore may not be able to be resolved.