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I heard that you have to include stdio.h before calling printf. Why?

Q

I heard that you have to include stdio.h before calling printf. Why?

✍: Guest

A

So that a proper prototype for printf will be in scope.
A compiler may use a different calling sequence for functions which accept variable-length argument lists. (It might do so if calls using variable-length argument lists were less efficient than those using fixed-length.) Therefore, a prototype (indicating, using the ellipsis notation ``...'', that the argument list is of variable length) must be in scope whenever a varargs function is called, so that the compiler knows to use the varargs calling mechanism.

2015-06-17, 764👍, 0💬

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