https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57951
--- Comment #2 from Frank Heckenbach <f.heckenb...@fh-soft.de> ---
Another bug that may be related to this one (and certainly depends
on it), originally reported as Debian bug #613551:
Tested with gcc-4.1 (apparently the last version that did allow "-MD -MG"):
When using "-MG", gcc doesn't give an error message, neither exits
with nonzero status when included files don't exist, even if not
only preprocessing ("-M"), but also when actually compiling ("-MD").
This can, in extreme cases, lead to miscompilation (if the included
file e.g. redefines existing macros), usually only to surprising
errors (the results of missing declarations from the include file,
without a leading hint to its absence).
% cat foo.c
#include "non-existing-file"
% gcc -MD -MG -c foo.c
% echo $?
0
