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From: "felix.von.s at posteo dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106940] New: Feature request: -Wsuggest-noexcept and
 -Wsuggest-explicit
Date: Wed, 14 Sep 2022 08:56:14 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106940

            Bug ID: 106940
           Summary: Feature request: -Wsuggest-noexcept and
                    -Wsuggest-explicit
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: felix.von.s at posteo dot de
  Target Milestone: ---

When writing classes, I routinely tend to forget that constructors can be u=
sed
for implicit conversions, unless marked explicit.

I also tend to forget about noexcept specifiers, which can lead to performa=
nce
pitfalls, especially with move constructors and move assignment operators.

So I would like a compiler warning that could remind me to consider such
concerns.  In case of noexcept, I don=E2=80=99t particularly need full sema=
ntic
analysis of the body; a pure syntax check whether the specifier is present
should suffice.  And in case of explicit, no other kind of check is possibl=
e,
obviously.

I imagine -Wsuggest-explicit could be suppressed for copy and move construc=
tors
from the same type.  I am undecided whether it should apply to conversion
operators, but leaning towards yes.

The warnings would be silenced by adding explicit specifiers: explicit(fals=
e)
and noexcept(false).  Each warning should probably require the earliest
language version where the respective silencing is possible (C++20 and C++1=
1,
respectively).=