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From: gah4 <gah4@u.washington.edu>
Newsgroups: comp.compilers
Subject: Re: what is defined, was for or against equality
Date: Mon, 10 Jan 2022 16:58:55 -0800 (PST)
Organization: Compilers Central
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On Saturday, January 8, 2022 at 10:11:55 AM UTC-8, Thomas Koenig wrote:

(snip)

> I see C conflating two separate concepts: Programm errors and
> behavior that is outside the standard. "Undefined behavior is
> always a programming error" does not work; that would make

> #include <unistd.h>
> #include <string.h>
> int main()
> {
> char a[] = "Hello, world!\n";
> write (1, a, strlen(a));
> return 0;
> }

Without the:

#include <unistd.h>

I agree that this would be undefined behavior.  But with the include file,
you are agreeing to use whatever standard the include file belongs to.

The include file defines the arguments to write(), but even more indicates
that you either supply (in another file), or use an otherwise supplied library
defining write().