.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH gnu::warning 3attr (date) "Linux man-pages (unreleased)"
.SH NAME
gnu::warning, gnu::error
\-
diagnose function calls not removed by optimizations
.SH SYNOPSIS
.nf
.BI [[gnu::warning( msg )]]
.BI [[gnu::error( msg )]]
.fi
.SH DESCRIPTION
This attribute can be applied to a function.
If the function call is not removed by optimizations,
a diagnostic is emitted.
The diagnostic contains the message
.I msg
and the location of the call in the source code.
.P
.B [[gnu::error()]]
terminates the compilation
after emitting the diagnostic.
.SH VERSIONS
.TP
.BI __attribute__((warning( msg )))
.TQ
.BI __attribute__((error( msg )))
.SH STANDARDS
GNU.
.SH HISTORY
gcc 4.3,
g++ 4.3,
clang 14,
clang++ 14.
.SH CAVEATS
This diagnostic is emitted by the compiler,
so it doesn't take into account linker optimizations.
.SH EXAMPLES
.EX
#include <stdlib.h>
\&
[[gnu::warning("foo")]] void dontcall(void);
\&
int
main(void)
{
	dontcall();  // Warning.
\&
	if (0)
		dontcall();  // No warning.
\&
	exit(EXIT_SUCCESS);
}
.EE