Adding upstream version 6.8.upstream/6.8upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 64 insertions, 0 deletions

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+.\" Copyright (C) 2022 Alejandro Colomar <alx@kernel.org>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.TH _Generic 3 2024-05-02 "Linux man-pages (unreleased)"
+.SH NAME
+_Generic \- type-generic selection
+.SH SYNOPSIS
+.nf
+.BR _Generic( \fIexpression\fP ", type1: " e1 ", " "... /*" \
+", default: " "e */" );
+.fi
+.SH DESCRIPTION
+.BR _Generic ()
+evaluates the path of code under the type selector
+that is compatible with the type of the controlling
+.IR expression ,
+or
+.B default:
+if no type is compatible.
+.P
+.I expression
+is not evaluated.
+.P
+This is especially useful for writing type-generic macros,
+that will behave differently depending on the type of the argument.
+.SH STANDARDS
+C11.
+.SH HISTORY
+C11.
+.SH EXAMPLES
+The following program demonstrates how to write
+a replacement for the standard
+.BR imaxabs (3)
+function, which being a function can't really provide what it promises:
+seamlessly upgrading to the widest available type.
+.IP
+.\" SRC BEGIN (_Generic.c)
+.EX
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+\&
+#define my_imaxabs  _Generic(INTMAX_C(0),  \e
+    long:           labs,                  \e
+    long long:      llabs                  \e
+/*  long long long: lllabs */              \e
+)
+\&
+int
+main(void)
+{
+    off_t  a;
+\&
+    a = \-42;
+    printf("imaxabs(%jd) == %jd\en", (intmax_t) a, my_imaxabs(a));
+    printf("&imaxabs == %p\en", &my_imaxabs);
+    printf("&labs    == %p\en", &labs);
+    printf("&llabs   == %p\en", &llabs);
+\&
+    exit(EXIT_SUCCESS);
+}
+.EE
+.\" SRC END