Trouble building xxhash for musl, musl-g++ not found

[makoConstruct]

Following instructions for building with musl here https://blog.rust-lang.org/2016/05/13/rustup.html

cargo build --target=x86_64-unknown-linux-musl

--- stderr
CMake Error at CMakeLists.txt:4 (project):
  The CMAKE_CXX_COMPILER:

    musl-g++

  is not a full path and was not found in the PATH.

  Tell CMake where to find the compiler by setting either the environment
  variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
  to the compiler, or to the compiler name if it is in the PATH.

This may just be a case of me not knowing where to find musl-g++. I've apt-get install musl-tools'd (which was not in the instructions, maybe it should be added? Before doing this, I was getting a musl-gcc not found error as well), which gave me musl-gcc, but no musl-g++. Searching debian's packages, I'm beginning to wonder if it really exists. Where is musl-g++ supposed to come from?

[alexcrichton]

I'm not actually sure of any official packaged way to get a C++ compiler targeting musl. For us at least we've always compiled our own compilers in this case...

[alexcrichton]

Oh I meant to close this at the time as in any case this isn't a Cargo bug, but likely with local configuration.

[estin]

@alexcrichton why musl-g++ needed for xxHash?

--- stdout                                                                                                                                  
running: "cmake" "/home/user/.cargo/registry/src/github.com-1ecc6299db9ec823/xxhash-sys-0.1.0/xxHash/cmake_unofficial" "-DCMAKE_INSTALL_PREF
IX=/home/user/prj/travels-task/target/x86_64-unknown-linux-musl/release/build/xxhash-sys-fbacfcd004ac9011/out" "-DCMAKE_C_FLAGS= -DXXH_NAMESPACE=__rust_xxhash_sys_ -ffunction-sections -fdata-sections -fPIC -m64 -static" "-DCMAKE_C_COMPILER=/usr/bin/musl-gcc" "-DCMAKE_CXX_FLAGS= $ffunction-sections -fdata-sections -fPIC -m64 -static" "-DCMAKE_CXX_COMPILER=musl-g++" "-DCMAKE_BUILD_TYPE=Release"                         
-- The CXX compiler identification is unknown                         
-- Configuring incomplete, errors occurred!                           
See also "/home/user/prj/travels-task/target/x86_64-unknown-linux-musl/release/build/xxhash-sys-fbacfcd004ac9011/out/build/CMakeFiles/CMake$utput.log".                        
See also "/home/user/prj/travels-task/target/x86_64-unknown-linux-musl/release/build/xxhash-sys-fbacfcd004ac9011/out/build/CMakeFiles/CMake$rror.log".                         

--- stderr                         
CMake Error at CMakeLists.txt:4 (project):                            
  The CMAKE_CXX_COMPILER:          

    musl-g++                       

  is not a full path and was not found in the PATH.                   

  Tell CMake where to find the compiler by setting either the environment                                                                   
  variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path                                                               
  to the compiler, or to the compiler name if it is in the PATH.

Ugly fix for me was (add musl-g++ to the PATH) - mock musl-g++ by any executable

$ sudo ln -s /bin/g++ /bin/musl-g++

And build was without any errors

$ ldd target/x86_64-unknown-linux-musl/release/travels-task
        not a dynamic executable

Not needed args are:

• "-DCMAKE_CXX_FLAGS= $ffunction-sections"
• "-DCMAKE_CXX_COMPILER=musl-g++"

It is cmake crate bug?
Or cargo bug?

Sorry about my poor English.

[alexcrichton]

It's probably just a bug in the xxhash build system that cmake requires a C++ compiler, the fix would probably go upstream to that project