https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102166
--- Comment #3 from Thiago Macieira <thiago at kde dot org> --- There appears to be some preprocessor magic behind the scenes because the preprocessed output can't be compiled either: $ gcc -no-integrated-cpp -Werror=implicit-function-declaration -c -xc test.cpp test.cpp: In function ‘amx’: test.cpp:10:5: error: implicit declaration of function ‘_tile_loadd’ [-Werror=implicit-function-declaration] 10 | _tile_loadd(0, 0, 0); | ^~~~~~~~~~~ test.cpp:11:5: error: implicit declaration of function ‘_tile_release’ [-Werror=implicit-function-declaration] 11 | _tile_release(); | ^~~~~~~~~~~~~ cc1: some warnings being treated as errors