How to resolve compiler warning 'implicit declaration of function memset'

Question

My c code uses \'memset\' and \'close\'. And I have added:

#include 
#include 
#include 

But I sti

Answer 1

Old question but I had similar issue and I solved it by adding

extern void* memset(void*, int, size_t);

or just

extern void* memset();

at the top of translation unit ( *.c file ).

Answer 2

Try to add next define at start of your .c file:

#define _GNU_SOURCE

It helped me with pipe2 function.

Answer 3

A good way to findout what header file you are missing:

 man <section> <function call>

To find out the section use:

apropos <function call>

Example:

 man 3 memset
 man 2 send

Edit in response to James Morris:

• Section | Description
• 1 General commands
• 2 System calls
• 3 C library functions
• 4 Special files (usually devices, those found in /dev) and drivers
• 5 File formats and conventions
• 6 Games and screensavers
• 7 Miscellanea
• 8 System administration commands and daemons

Source: Wikipedia Man Page

Answer 4

You need:

#include <string.h> /* memset */
#include <unistd.h> /* close */

in your code.

References: POSIX for close, the C standard for memset.

Answer 5

memset requires you to import the header string.h file. So just add the following header

#include <string.h>
...