https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91187
--- Comment #5 from Albert Astals Cid <aacid at kde dot org> ---
(In reply to Harald van Dijk from comment #3)
> If the header files cannot be modified, the -isystem command-line option
> also causes included files to be treated as system headers where warnings
> are suppressed.
The thing is, this isn't happening. If you compile the attached main-glib.cpp
with
g++ -c -Wzero-as-null-pointer-constant main.cpp -isystem /usr/include/glib-2.0/
-isystem /usr/lib/glib-2.0/include
i still get
main.cpp: In function ‘GType poppler_annot_get_type()’:
main.cpp:17:1: warning: zero as null pointer constant
[-Wzero-as-null-pointer-constant]
17 | G_DEFINE_TYPE (PopplerAnnot, poppler_annot, G_TYPE_OBJECT)
| ^~~~~~~~~~~~~
