Use of 'cpp' extension for non-C++ (and non-C) files to be processed with cpp causes unnecessary requirement for cc1plus during build, build process exits 0 even if it's missing

Submitted by Adam Williamson

Assigned to Xorg Project Team

Link to original bug (#107368)

Description

Fedora recently removed gcc and gcc-c++ from the default buildroot, meaning packages that need these compilers have to explicitly BuildRequire them. Our xorg-x11-xinit package BuildRequired gcc, but not gcc-c++. Somehow, a build run under these conditions completed, even though it was obviously heavily broken:

https://koji.fedoraproject.org/koji/buildinfo?buildID=1127335
https://kojipkgs.fedoraproject.org//packages/xorg-x11-xinit/1.4.0/2.fc29/data/logs/x86_64/build.log

Note the clear errors in the build.log:

cpp: error trying to exec 'cc1plus': execvp: No such file or directory
cpp: error trying to exec 'cc1plus': execvp: No such file or directory

yet somehow, the 'make -j6' command must have exited 0, or else the package build would have aborted at that point.

The result was a 'successful' package build with a zero-length startx (and probably other weirdness, that's just the only symptom I noticed). Obviously, 'make' should exit with a non-zero exit code in this case.