Ubuntu 22.04 + UE4.26, can't make launch because of issues with math modules of C compiler

[eleuven111]

Hi,

I'm currently building CARLA (latest version from GitHub) on Ubuntu 22.04 using Clang 10 and libc++ as required by UE4.26. Compilation is done through the usual make launch process.

Everything builds fine up to the point where LibCarla is compiled, but I keep getting errors from the math.h header (specifically libc++'s version under ThirdParty/Linux/LibCxx/include/c++/v1). For example:

error: no member named 'ceilf' in the global namespace
error: no member named 'cosf' in the global namespace

These errors happen inside math.h itself, at lines like:

inline _LIBCPP_INLINE_VISIBILITY float cos(float x) _NOEXCEPT { return ::cosf(x); }

which fails because apparently ::cosf isn’t found.

The compile command clearly shows that -stdlib=libc++ and the correct -isystem path are set multiple times, and everything is going through /opt/llvm-10/bin/clang++. No trace of g++ anywhere.

Additionally, is already properly included in all the relevant .cpp files that use math functions like cos, ceil, pow, atan2, etc.

At this point I don’t know if:

• libc++ is missing symbols on this setup
• something is off in how UE or CARLA overrides toolchains
• or this is some weird interaction with the math headers

Any idea what's missing or misconfigured here?

Thanks.

[RobinSchmid7]

You can try to edit the toolchain:

Change the CarlaUE5/CMake/Toolchain.cmake and replace lines 89-94 with:

add_compile_options (
	-fms-extensions
	-fno-math-errno
	-fdiagnostics-absolute-paths
	-D_GNU_SOURCE
	$<$<COMPILE_LANGUAGE:CXX>:-stdlib=libc++>
)

then also change line 96:

add_link_options (-stdlib=libc++ -L${UE_LIBS} -lm)

or use another math library?

[eleuven111]

Hello, thanks so much for your hint.

I just realized that if I use the command make setup, everything compiles properly. It fails if I use make launch.

When I use make setup, my clang10 compiler is used, but with make launch, it seems that the lighter version of UE4.26 is used and that one lacks basic libraries.

Any idea to force the use of clang10 under make launch?

Thanks again.