about including header files

[Andrew Haley]

yacson wrote:
> Hi everybody.
> what happens if a "header include" is missing? because I unexpectedly notice
> that  this code:
> main()
> {printf("hello");}
> 
> works in linux(at least on my (mandriva spring 2007 )box) while it does not
> in windows(turbo C++).
> so finally, can I say :  #include <stdio.h> is not always necessary!

Strictly speaking, I think this is undefined behaviour.  So, while it
might work, it's not correct code, and it may break at any time.

> another question is : where does the compiler (or the linker) find the
> actual code of printf (whether or not one has written its prototype)

It's in the C library.  The C library is not part of gcc.

Andrew.