warning: implicit declaration of function ‘malloc’

This is a discussion on warning: implicit declaration of function ‘malloc’ within the C Programming forums, part of the General Programming Boards category; What do these warnings mean? Code: 12.8.c: In function ‘insert’: 12.8.c:29: warning: implicit declaration of function ‘malloc’ 12.8.c:29: warning: incompatible ...

  1. #1
    Registered User
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    warning: implicit declaration of function ‘malloc’

    What do these warnings mean?

    Code:
    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’
    Code:
    #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" );
    	}
    }

  2. #2
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    Code:
    #include <stdlib.h>

  3. #3
    Registered User
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    thanks

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    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.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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