CLONE_VM undeclared (first use in this function)

Question

I am using the clone feature in linux c.

However, I encountered the error CLONE_VM undeclared (first use in this function) when I tried to compile my code.

I went to google for solutions and one of the site mentioned that #include <sched.h> must be included inside the code. I have already included #include <sched.h> in my code but the compilation error still persists.

Any help? :)

int c = clone(child,p+STACKSIZE-1,CLONE_VM|SIGCHLD,NULL) ;

Don't use `clone`. Use the standard pthread library. The `clone` syscall is mostly for implementors of Posix threads. — Basile Starynkevitch, Mar 17 '14 at 09:10

Lee Duhem · Accepted Answer · 2014-03-17T08:17:37.623

12

Add the following lines to the beginning of your code

   #define _GNU_SOURCE             /* See feature_test_macros(7) */
   #include <sched.h>

You could find out which header files and/or macros are needed by

man 2 syscall_name
man 3 library_function_name

By the way, the implication of _GNU_SOURCE and more could be find out by man 7 feature_test_macros.

edited Mar 17 '14 at 08:17

answered Mar 17 '14 at 08:09

Lee Duhem

14,695
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Thanks! It worked! May I know what does the _GNU_SOURCE does? – Lawrence Wong Mar 17 '14 at 08:12
Nevermind. I found my answer here. http://stackoverflow.com/questions/5582211/what-does-define-gnu-source-imply – Lawrence Wong Mar 17 '14 at 08:13
@LawrenceWong You could find it out by `man 7 feature_test_macros` – Lee Duhem Mar 17 '14 at 08:16

score 1 · Answer 2 · answered May 29 '19 at 11:00

1

sometime including #include <sched.h> will not work, so point sched.h file from linux. i.e. #include <linux/sched.h>

answered May 29 '19 at 11:00

Sushil Kumar

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For me it worked when I put "#define _GNU_SOURCE" then "#include " on *top* of the source code (above all other #includes). – ZeZNiQ Oct 04 '19 at 16:39

CLONE_VM undeclared (first use in this function)

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