[compiler-rt] Fix building on OpenBSD/amd64

[brad0]

OpenBSD/amd64 does not use multi-lib. Enabling the CET support on amd64
exposed that CMake was using a multi-lib build on amd64.

OpenBSD 64-bit platforms do not support multi-lib.

[brad0]

@vitalybuka Ping.

[ojhunt]

I'm not sure about this.

If the pointer size conditions really are necessary, then adding the OPENBSD definition seems like a better approach, although perhaps a better solution would be to work out why test_target_arch is not working on OBSD, and fixing that test macro.

If the problem with the test macro are resolvable, then it might be ok to retain the (NOT STREQUAL) version, but I would be perfectly ok with adding an OPENBSD definition and using that, though open to dissent from others :D

[ojhunt]

Is this OpenBSD specific, or BSD in general and simply hasn't been hit on them yet?

If is OpenBSD specific is there a central config file that is included in all the cmake scripts where you could add something like

# I'm blindly assuming `DEFINED` is an operator and not a special form # of `if`, if the latter this would become if () else() ...set ... endif() if (NOT (DEFINED OPENBSD)) # I also do not know if CMake allows this, because I'm unsure what # things are special forms vs operators, because I'm not a cmake person  set(OPENBSD ("${CMAKE_SYSTEM_NAME}" STREQUAL "OpenBSD")) endif()

Then OPENBSD and NOT OPENBSD become available and the script would read better.

Or maybe OPEN_BSD if that seems more appropriate.

I have the existence check because it seems possible that cmake might add a builtin like this in the future?

[brad0]

Is this OpenBSD specific, or BSD in general and simply hasn't been hit on them yet?

OpenBSD specific. FreeBSD / NetBSD support multi-lib.

If is OpenBSD specific is there a central config file that is included in all the cmake scripts where you could add something like

# I'm blindly assuming `DEFINED` is an operator and not a special form # of `if`, if the latter this would become if () else() ...set ... endif() if (NOT (DEFINED OPENBSD)) # I also do not know if CMake allows this, because I'm unsure what # things are special forms vs operators, because I'm not a cmake person  set(OPENBSD ("${CMAKE_SYSTEM_NAME}" STREQUAL "OpenBSD")) endif()

Then OPENBSD and NOT OPENBSD become available and the script would read better.

Or maybe OPEN_BSD if that seems more appropriate.

I have the existence check because it seems possible that cmake might add a builtin like this in the future?

That seems pretty gross. We don't even use LINUX essentially anywhere and it actually does exist from CMake.

[ojhunt]

Why are these needed, my assumption is that test_target_arch should be handling this automatically?

[ojhunt]

(edit: I had misremembered the x86 path when I wrote the original comment)

[ojhunt]

ditto

[vitalybuka]

Leaving for @ojhunt

[brad0]

If the pointer size conditions really are necessary, then adding the OPENBSD definition seems like a better approach, although perhaps a better solution would be to work out why test_target_arch is not working on OBSD, and fixing that test macro.

There is no variable OPENBSD. The variables such as MSVC comes from CMake. I'm not sure what you mean by why test_target_arch is not working on OBSD. It's doing what it should be.

If the problem with the test macro are resolvable, then it might be ok to retain the (NOT STREQUAL) version, but I would be perfectly ok with adding an OPENBSD definition and using that, though open to dissent from others :D

The variables like this come from CMake. This is the same way things are done elsewhere in compiler-rt and the rest of the LLVM codebase.