https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104023
--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> --- Oh no. We usually use .cpp/.cc extension as an additional file that is intentionally skipped by a glob pattern: $ head g++.target/i386/mv12.C ... // { dg-additional-sources "mv12-aux.cc" } or: gcc/testsuite/g++.dg/asan/asan_test.C:#include "asan_str_test.cc"