When building with clang and changing a file that is part of the precompiled header, you can get:

fatal error: file '/Users/staffan/mercurial/jdk9-hs-rt/hotspot/src/share/vm/runtime/thread.hpp' has been modified since the precompiled header was built

clang behaves differently than gcc here.


Example with clang:

$ ls
test.h
$ cat test.h
#include <stdio.h>
$ clang -x c-header -include test.h test.h -o test.h.pch
$ touch test.h
$ clang -x c-header -include test.h test.h -o test.h.pch
fatal error: file '/Users/staffan/tmp/pch/test.h' has been modified since the precompiled header was built
1 error generated.

Same with gcc:

$ ls
test.h
$ cat test.h
#include <stdio.h>
$ gcc -x c-header -include test.h test.h -o test.h.pch
$ touch test.h
$ gcc -x c-header -include test.h test.h -o test.h.pch