[Bug preprocessor/52566] #include with #pragma once and files' contents is the same

[terra at gnome dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

--- Comment #5 from M Welinder <terra at gnome dot org> ---
>From 108101:

Note also:

# gcc -MM c.c
c.o: c.c a.h

No b.h present!

I.e., Makefiles built with this will not pick up changes to the second file.