configure: error: C++ compiler missing or inoperational about spack

[adamjstewart]

I think the cause of the problem is that either Spack was broken when you first checked it out and it has been fixed since then, or you didn't have a C++ compiler when you first checked Spack out and have installed one since then. Spack isn't yet smart enough to look for missing compilers after the fact.

[weijianwen]

Thank you, @adamjstewart . Readding compiler via spack compiler find after removing ~/.spack/compilers.yaml and ~/.spack/<OS>/compilers.yaml works for me!

# rm -rf ~/.spack/compilers.yaml; rm -rf ~/.spack/linux/compilers.yaml; bin/spack compiler find
==> Added 1 new compiler to /root/.spack/linux/compilers.yaml
    [email protected]

# bin/spack compiler info [email protected]
[email protected]:
        paths:
                cc = /usr/bin/gcc
                cxx = /usr/bin/g++
                f77 = /usr/bin/gfortran
                fc = /usr/bin/gfortran
        modules  = []
        operating system  = centos7

[tgamblin]

The links point at cc because that's the compiler wrapper that inserts RPATHs:
http://scalability-llnl.github.io/spack/packaging_guide.html#the-install-environment

lib/spack/env is put first in your path during a build to control the environment, but the error messages aren't that great, and I have not tested much on ubuntu (though apparently I should -- maybe travis is a good place to do this).

Have you looked at ~/.spackconfig to see whether your compilers are set up correctly? By default Spack will use the latest gcc to build, so if that is not set properly (e.g. if it has "None" for cc or c++) things will break.

[chvillanuevap]

I have the following in my .spackconfig file:

[compiler "[email protected]"]
    cc = /usr/bin/gcc
    cxx = None
    f77 = /usr/bin/gfortran
    fc = /usr/bin/gfortran

It seems Ubuntu sets the variables g++, c++, and cpp, but not cxx.

[tgamblin]

Is there a /usr/bin/g++? If so can you send the output of gcc -dumpversion AND g++ -dumpversion?

The autodetection in Spack is done via per-compiler classes. Look at lib/spack/spack/compilers/.py, each of which extends Compiler in lib/spack/spack/compiler.py. Compiler detection is done by searching your PATH in parallel and locating all the executables with names like gcc, g++*. It then detects the version of each and groups them by version -- it looks like there was something wrong when it ran g++, OR it didn't match the others.

[chvillanuevap]

Yes, there is:

ls /usr/bin/g++
lrwxrwxrwx 1 root root 7 Apr  7  2014 /usr/bin/g++ -> g++-4.8

Both gcc -dumpversion and g++ -dumpversion return 4.8. cc, gfortran, cpp, and c++ also return 4.8.

[tgamblin]

I'll have to find an ubuntu machine to test on sometime soon. In the meantime, if you add back /usr/bin/g++ for cxx, then things should work better for you. Spack should really warn if it doesn't find some of the compilers.

[chvillanuevap]

In lib/spack/spack/compilers/__init__.py, in line 181, there is a check:

        if not all(n in items for n in _required_instance_vars):
            raise InvalidCompilerConfigurationError(cspec)

Even though cxx is set to None, this check does not raise an exception because items does have cxx as a key. _required_instance_vars is a list with ['cc','cxx','f77','fc'], while items is a dictionary.

[tgamblin]

Does that fix it for you? If so can you send a PR? I can put the change in as well but I cannot verify it right now.

[chvillanuevap]

My first fix was to create a symbolic link /usr/bin/cxx -> /usr/bin/cpp in the command line. It seems Ubuntu does not have a cxx symbolic link by default.

My second fix (and the more generic one) was to modify _required_instance_vars (in lib/spack/spack/compilers/__init__.py) to include cpp rather than cxx, and to change the Compiler attribute self.cxx to self.cpp to match the variable in _required_instance_vars.

I do not know if you wish to change the cxx variable to cpp, but if you do, I can send a PR.

[adamjstewart]

Does this bug still occur? Specifically, the part about Spack not picking up g++ on Ubuntu. It seems like all of the other bugs mentioned in this issue stem from that fact.

[tgamblin]

I added some compiler checks to the Travis CI output, and indeed at least on the Travis Ubuntu distro, cxx is found properly. Closing for now -- please reopen if this happens again.

[weijianwen]

Hi. This happens agin on Cent OS 7. spack fails to identify g++ shipped with the OS, which leads to configuration failure during [email protected] installation.

bin/spack compiler info [email protected]
[email protected]:
        paths:
                cc = /usr/bin/gcc
                cxx = None
                f77 = /usr/bin/gfortran
                fc = /usr/bin/gfortran
        modules  = []
        operating system  = centos7

ls /usr/bin/g++
/usr/bin/g++

[adamjstewart]

@weijianwen Do you have a /usr/bin/g++? If you delete ~/.spack/compilers.yaml and/or ~/.spack/<OS>/compilers.yaml and run spack compiler find, does it pick it up the second time?