Request: consider splitting out time_generator functionality / adding a cmake option?

[13steinj]

uuid/CMakeLists.txt

Lines 25 to 29 in e7fcbc1

	if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
	target_link_libraries(boost_uuid INTERFACE atomic)
	endif()

It's unclear if the above lines are correct (considering I needed to manually change the tests on Clang to link against libatomic; but this may be an artifact of my organization's eccentric toolchain); however, by forcing all downstream consumers to link against libatomic on GCC; even those that don't use the time_generator functionality, this makes the library unsuitable for some high-performance environments (in our case; we intentionally don't link against libatomic since we want to use the intrinsics at all times or fail, and we do not supply libatomic on production machines for the same reason).

I was originally going to suggest relying on autolinking, but then found out that apparently GCC doesn't support it.

For what it's worth, I've gone the cmake-option route in our (fork? fork feels like the wrong term but I guess it's accurate?).

It's also possible that simply using Boost.Atomic instead of STL atomics would suffice as well (I'm unfamiliar with what Boost.Atomic does in such an environment / if it in some way also relies on libatomic).

[pdimov]

I agree that a CMake option seems the best way to approach this.

Clang under Linux using libstdc++ very likely needs -latomic as well, I'm not sure about Clang/Linux using libc++. I don't see a simple way to detect the stdlib. One can always do a configure check, I suppose.

My CMake CI only uses the system compiler, so testing for GCC was enough to make it pass.

[pdimov]

Looks like -latomic is required on Linux even when using libc++: https://godbolt.org/z/hKv1z89aE

[13steinj]

I'm not sure about Clang/Linux using libc++.

For reference on our eccentric toolchain; we use GCC + libstdc++ or Clang + libc++ (no "cross"), for historical (and, despite issues, quirky) reasons. So yeah, needed under clang + libc++ (bad timing between my response and you looking into it).

[pdimov]

CMake option added to develop.

[pdimov]

Merged to master.