C warning implicit declaration of function 'exit'

Question

This is my warning.

implicit declaration of function 'exit'

How i can remove it.

i am using linux & gcc compiler.

`man 3 exit` will show you the header to include. – Mar 09 '10 at 07:01 — , Mar 09 '10 at 07:01

score 137 · Accepted Answer · answered Mar 09 '10 at 06:05

137

Add:

#include <stdlib.h>

to the top of your program.

answered Mar 09 '10 at 06:05

Greg Hewgill

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@Greg Hewgill: In my program, I have not used `#include ` and I am getting this warning only when I use `-Wall` option. Otherwise the program compiles fine and executable runs properly. This means that gcc is somehow able to link to the file without my including it. How is that happening? – Lazer May 06 '10 at 16:13
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@eSKay: Implicit declarations are *permitted* in C unless you use the `-Wmissing-protypes` warning switch (which is turned on by `-Wall`). – Greg Hewgill May 06 '10 at 19:17

score 12 · Answer 2 · answered Mar 09 '10 at 06:06

12

Do you have this preprocessor? If not, add it.

#include <stdlib.h>

answered Mar 09 '10 at 06:06

shinkou

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score 2 · Answer 3 · answered Dec 01 '14 at 10:24

exit() is a library function, the respecive prototypes are present in the stdlib.h header file, inoder to call the process to specified code for exit function, you need to attach the as #include stdlib.h header in your program. that is the reason we should add the stdlib.h header. eventhough you can run the program, but it shows the warning message like below:

warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default]

but, this kind of program not recommended, we need to take care of what we are given in the program,be cautious. warning may leads runtime error.

C warning implicit declaration of function 'exit'

3 Answers3