Linux cli command _Generic

➡ A Linux man page (short for manual page) is a form of software documentation found on Linux and Unix-like operating systems. This man-page explains the command _Generic and provides detailed information about the command _Generic, system calls, library functions, and other aspects of the system, including usage, options, and examples of _. You can access this man page by typing man followed by the _Generic.

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NAME 🖥️ _Generic 🖥️

type-generic selection

SYNOPSIS

_Generic(expression, type1: e1, ... /*",default: e*/");

DESCRIPTION

_Generic() evaluates the path of code under the type selector that is compatible with the type of the controlling expression, or default: if no type is compatible.

expression is not evaluated.

This is especially useful for writing type-generic macros, that will behave differently depending on the type of the argument.

STANDARDS

C11.

HISTORY

C11.

EXAMPLES

The following program demonstrates how to write a replacement for the standard imaxabs(3) function, which being a function can’t really provide what it promises: seamlessly upgrading to the widest available type.

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#define my_imaxabs  _Generic(INTMAX_C(0),  \
    long:           labs,                  \
    long long:      llabs                  \
/*  long long long: lllabs */              \
)
int
main(void)
{
    off_t  a;
    a = -42;
    printf("imaxabs(%jd) == %jd

“, (intmax_t) a, my_imaxabs(a)); printf("&imaxabs == %p “, &my_imaxabs); printf("&labs == %p “, &labs); printf("&llabs == %p “, &llabs); exit(EXIT_SUCCESS); }

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