clone() function implicit declaration

Question

I am using the function clone() to create threads. The problem is that I am having this error during compilation:

implicit declaration of function ‘clone’ [-Wimplicit-function-declaration]

I included <linux/sched.h>. What can be the problem?

`man clone` - what does it tell you to include? – Mat May 10 '14 at 09:28 — Mat, May 10 '14 at 09:28

score 3 · Accepted Answer · edited May 23 '17 at 12:14

3

Add the following lines at the top of you source file

#define _GNU_SOURCE  
#include <linux/sched.h>        /* or #include <sched.h> */

_GNU_SOURCE is a Feature test macro.

Feature test macros allow the programmer to control the definitions that are exposed by system header files when a program is compiled. In order to be effective, a feature test macro must be defined before including any header files. This can be done either in the compilation command (cc -DMACRO=value) or by #define-ing the macro within the source code before #include-ing any headers.

edited May 23 '17 at 12:14

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answered May 10 '14 at 09:34

TheCodeArtist

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I suppose the **`_GNU_SOURCE`** macro still needs to be defined. – TheCodeArtist May 10 '14 at 09:52
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Yes, unless you're using a `-std` mode that already sets it (the gnuXXX modes do AFAIR) – Mat May 10 '14 at 09:54

clone() function implicit declaration

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