Set Trilinos_USE_GNUINSTALLDIRS=ON for Trilinos 15.0

[bartlettroscoe]

CC: @sebrowne, @ccober6

Description

TriBITS has had the ability to use that paths selected by the standard CMake module GNUInstallDirs.cmake for a long time (see Setting the install prefix). But it is turned off in TriBITS by default (for the sake of backward compatibility) and it was never turned on in Trilinos by default (also to maintain backward compatibility).

Therefore, in the goal to move Trilinos and TriBITS to modern CMake ( see TriBITSPub/TriBITS#411), we should hard set the non-cache variable Trilinos_USE_GNUINSTALLDIRS=ON in the base Trilinos CMakeLists.txt file. This will force every Trilinos user to absorb this change in Trilinos 15.0 (but most customers should never even notice).

Once Trilinos 15.0 comes out, then we can refactor TriBITS to just directly use the standard variables that come from the standard CMake module include(GNUInstallDirs).

Easy as pie (at least for Trilinos and TriBITS).

[bartlettroscoe]

FYI: There may be a defect in CMake that may be problematic to customers, at least for CMake 3.23.1 (see https://gitlab.kitware.com/cmake/cmake/-/issues/25157).

[sebrowne]

Yes, that could be obnoxious. I think it mostly affects SUSE IIRC. Still, probably good to merge this after 14.4. A step in the right direction.

[sebrowne]

@bartlettroscoe would you like me to do this now that 14.4 is out?

[bartlettroscoe]

@bartlettroscoe would you like me to do this now that 14.4 is out?

Yes. But we need to make sure and write a release note for this and this may break people's existing configurations (because it will install libs in <prefix>/libs64/ instead of in <prefix>/libs/ and that is likely to break some things). For example, see https://gitlab.kitware.com/cmake/cmake/-/issues/25157. So they may need to change their configure arguments like I had to do in:

• https://github.com/TriBITSPub/TriBITS/pull/591/files

See:

https://github.com/TriBITSPub/TriBITS/blob/04b19accca4db76aa767bd916349fc9afbb18619/test/core/ExamplesUnitTests/TribitsExampleProject2_Tests.cmake#L684-L696

[bartlettroscoe]

because it will install libs in <prefix>/libs64/ instead of in <prefix>/libs/ and that is likely to break some things

As predicted:

• Failing Albany configures due to incorrect Trilinos version sandialabs/Albany#982

[bartlettroscoe]

With the merging of #12258 (and the follow-ups dealing with customers and broken configurations), this is complete.