LLVM_full_jll does not contain clang++

[tkf]

To use LLVM 10 to build julia, I needed to add a symlink clang++ manually like this JuliaLang/julia#35341 (comment):

tooldir=$HOME/.julia/artifacts/8cd56e3e81e5770720c31304026f3b23f129153e/tools
cd $tooldir
ln -s clang-10 clang++
cd -
... PATH="$tooldir:$PATH" make USECLANG=1 ...

Is it intentional that LLVM_full_jll contains a symlink clang but not clang++? If not, can this be added to the distribution?

[vchuravy]

clang++ vs clang makes no difference in my experience. But we don't do anything different from the upstream project here.

[tkf]

Specifying CXX=$tooldir/clang did work for me but I thought it'd be nice if I can just set PATH="$tooldir:$PATH" as then make would pick up other CLIs like llvm-config and llvm-symbolizer.

So maybe it's better to set CXX to clang when USECLANG? Currently it's CXX := $(CROSS_COMPILE)clang++.

[maleadt]

clang++ vs clang makes no difference in my experience.

It does change the default language selection:

tim@taurus /tmp$ cat test.h                                                                                                                                                                                                                                                   
#ifdef __cplusplus
#error C++
#else
#error C
#endif

tim@taurus /tmp$ clang test.h                                                                                                                                                                                                                                                 
test.h:4:2: error: C
#error C
 ^
1 error generated.

tim@taurus /tmp$ clang++ test.h                                                                                                                                                                                                                                               
clang-9: warning: treating 'c-header' input as 'c++-header' when in C++ mode, this behavior is deprecated [-Wdeprecated]
test.h:2:2: error: C++
#error C++
 ^
1 error generated

But we don't do anything different from the upstream project here.

When building LLVM/Clang with the Julia build system but not using BB we do get a symlink:

$ ls -la ./deps/llvm-6.0.1/build_Release/bin/clang++
lrwxrwxrwx 1 maleadt maleadt 9 Mar 29 16:19 ./deps/llvm-6.0.1/build_Release/bin/clang++ -> clang-6.0

And this seems to be done by upstream: https://github.com/llvm/llvm-project/blob/717a460867633008520713614018f3c37503a5ca/clang/tools/driver/CMakeLists.txt#L65-L71

So for consistency, and to make the LLVM_full tarball as usable as possible as a toolchain outside of Julia, it would be useful if it included these symlinks.

[vchuravy]

Huh, I then wonder why we don't. Didn't change the buildscript in any way. Happy to take PRs