https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100462
--- Comment #6 from Marco Trevisan <mail at 3v1n0 dot net> --- (In reply to Jakub Jelinek from comment #5) > As documented - see > https://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html - PCH is only > tried if no C token is seen before the #include directive (comments and > preprocessor directives like #if/#ifdef/#define/#undef are fine, but e.g. > #pragma is not). > So, is #include "gjs_pch.hh" the first thing in your sources? Well it's not because I instead was following the approach of > This also works with -include. So yet another way to use precompiled headers, > good for projects not designed with precompiled header files in mind, is to > simply take most of the header files used by a project, include them from > another header file, precompile that header file, and -include the > precompiled header. If the header files have guards against multiple > inclusion, they are skipped because they’ve already been included (in the > precompiled header). Thus, `-include` is ignored here it seems... Because it comes after another include... As per this I think the minimal reproducer is actually easy to have: // main.c int main(int argc, char**argv) { std::string s = "Hi"; return 0; } // header.h #include <string> ---- mkdir _build g++ -c header.h -o _build/gjs_pch.h.gch # Works g++ -I _build main.c -o main -include string -include gjs_pch.h # Fails g++ -I _build main.c -o main -include string -include gjs_pch.h cc1plus: fatal error: gjs_pch.h: No such file or directory So, in this case I'm not sure that the pch should be ignored...
