https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92631
Bug ID: 92631
Summary: Warnings partly caused by system headers are broken
Product: gcc
Version: 9.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: mwoehlke.floss at gmail dot com
Target Milestone: ---
While trying to fix warnings in a code base, we noticed that some are very
strange:
foo.cpp: warning: by ‘virtual ...’ [-Werror=overloaded-virtual]
bar.cpp: warning: but ‘...’ does not throw; perhaps it should be declared
‘noexcept’ [-Wnoexcept]
The commonality is that all of these are the second part of a multi-part
warning. The first part of the warning IS NOT SHOWN. Further testing proved
that the problem isn't on our end (misreading the log or some such); gcc NEVER
printed the first part of the warning. Additionally, the file reference for the
missing first part would be in a "system" header.
Needless to say, this makes for some *very* confusing warnings.
Attempting to compile the following example will reproduce the issue:
==> foo.cpp <==
#pragma GCC diagnostic error "-Woverloaded-virtual"
#include "foo.h"
struct bar : foo
{
void frob(int) override;
}
==> foo.h <==
#pragma GCC system_header
struct foo
{
virtual void frob(int);
virtual void frob(long);
};
(Compile with 'g++ foo.cpp'.)
Adding -Wsystem-headers "reveals" the missing first part of the
warnings/errors.
(Apologies if this is a duplicate and I have overlooked a similar report.)
