[Bug c++/61412] Warnings incorrectly suppressed when compiling previously preprocessed file

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61412

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Matt Godbolt from comment #0)
> --begin example
> # 88 "some/file.cpp" 3 4
> struct Foo { int i, j; Foo() : j(1), i(0) {} };
> --end example

How did you produce that file?  If you compile the exact preprocessor output
you shouldn't have a problem. If you mangle it, fooling the compiler into
thinking it's in a system header, you have a problem.