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Re: Avoid clang warnings regarding [[__nodiscard__]]
From: |
Bruno Haible |
Subject: |
Re: Avoid clang warnings regarding [[__nodiscard__]] |
Date: |
Sat, 28 Jan 2023 20:22:33 +0100 |
Paul Eggert wrote:
> > + /* With clang up to 15.0.6 (at least), in C++ mode, [[__nodiscard__]]
> > produces
> > + a warning. */
> > +# if __clang_major__ >= 1000
>
> I found this a little hard to follow
Indeed, I wondered whether I should add a comment. Guess I should have :)
> How about something like the attached, to simplify this for Clang non-experts?
I wanted the code to be prepared for the day when clang++ actually adds
support for this syntax [[__nodiscard__]]. The code you are proposing
optimizes the current needs, but not the future needs.
I'm adding this comment instead. I hope that's clear enough.
2023-01-28 Bruno Haible <bruno@clisp.org>
Clarify _GL_ATTRIBUTE_NODISCARD code.
Reported by Paul Eggert.
* m4/gnulib-common.m4 (gl_COMMON_BODY): Add comment regarding
_GL_ATTRIBUTE_NODISCARD definition.
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index d632819864..c0181abdc5 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -381,7 +381,10 @@ AC_DEFUN([gl_COMMON_BODY], [
#ifndef _GL_ATTRIBUTE_NODISCARD
# if defined __clang__ && defined __cplusplus
/* With clang up to 15.0.6 (at least), in C++ mode, [[__nodiscard__]]
produces
- a warning. */
+ a warning.
+ The 1000 below means a yet unknown threshold. When clang++ version X
+ starts supporting [[__nodiscard__]] without warning about it, you can
+ replace the 1000 with X. */
# if __clang_major__ >= 1000
# define _GL_ATTRIBUTE_NODISCARD [[__nodiscard__]]
# endif