incompatible implicit declaration

[Robert Plantz]

On 12/26/2010 8:30 AM, Jonathan Wakely wrote:
> On 26 December 2010 06:58, ali hagigat wrote:
>> Please look at the following program:
>>
>> main(){
>>         printf("func1= %d\n", func1(10));
>> }
>>
>> /root/tmp3>  gcc -c -o prog1.o prog1.c
>> prog1.c: In function ‘main’:
>> prog1.c:6: warning: incompatible implicit declaration of built-in
>> function ‘printf’
>> -------------------------------------------------------------------
>> Why the declaration of printf is incomplete?
> http://c-faq.com/varargs/protos.html
>
#include-ing header files is always a good idea because the prototype statements ensure that you have called the function properly. That is, they are your friend.