https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89160
Bug ID: 89160
Summary: -Wattributes too eager on C++11 attributes
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: glisse at gcc dot gnu.org
Target Milestone: ---
A random testcase to illustrate:
[[hahaha]] int i;
$ g++-snapshot a.c -c -std=gnu++2a
a.c:1:16: warning: 'hahaha' attribute directive ignored [-Wattributes]
1 | [[hahaha]] int i;
| ^
The standard, in [dcl.attr.grammar], says: "Any attribute-token that is not
recognized by the implementation is ignored." I believe the intent is that it
should be **silently** ignored, unless I really ask for it clearly with
something like -Wunknown-c++-attribute (definitely not part of -Wall). There is
a strong requirement that standard attributes have to be safe to ignore. I
believe I should be able to use newer (C++20) attributes without having older
(C++17) compilers complain so noisily. Sadly, clang is just as bad, and ISTR
reading that visual studio was even worse, rejecting programs with C++17
attributes in C++14 mode. As a result, we keep having to write a lot of
preprocessor nonsense :-(
