warning: implicit declaration of function ‘malloc’

[yougene]

What do these warnings mean?

12.8.c: In function ‘insert’:
12.8.c:29: warning: implicit declaration of function ‘malloc’
12.8.c:29: warning: incompatible implicit declaration of built-in function ‘malloc’

#include <stdio.h>

struct listnode {
	int num;
	struct listnode *nextPtr;
};

typedef struct listnode ListNode;

void insert( ListNode **sPtr, int number );




int main()
{
//	printf( "Hello, world\n" );
	
	return 0;
}




void insert( ListNode **sPtr, int number )
{
	ListNode *newPtr;

	newPtr = malloc( sizeof( ListNode ) );

	if ( newPtr != NULL ) {
		printf( "hello" );
	}
}

[cyberfish]

#include <stdlib.h>

[yougene]

thanks

[Elysia]

It means you failed to include the proper header for the function you are trying to call. Don't let yourself be mislead by the compiler saying it's a warning; it's actually a very serious error.