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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: gcc and 'include'
Date: Thu, 26 Mar 2026 16:12:47 -0700
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Bart <bc@freeuk.com> writes:
> Take this program:
>
>   #include <stdlib.h>
>
>   inline int F(){return rand();}
>
>   int main(void) {
>       return F();
>   }
>
> This compiles fine with gcc using -O1 -O2 -O3.
>
> But compile without optimising, and it fails to link as it can't find
> a function 'F'.
>
> Is it supposed to behave like that? I assume no discrete function F is
> being generated because of the 'inline' attribute, but you'd think it
> would ignore that if inlining wasn't enabled.
>
> It compiles fine with or without 'inline' using tcc and bcc (my product).
>
> Clang fails too, but clearly only because it has to duplicate gcc's
> behaviour for drop-in compatability, even if it is crass.
>
> (This is the actual program:
> https://web.archive.org/web/20010127204000/http://www.bagley.org/~doug/shootout/bench/lists/lists.gcc)

I don't have an answer to your question, but defining F as
"static inline" makes the program work.  You can also do this:

    inline int F();
    int F(){return rand();}

(Unless you're using a C23 compiler, I suggest "int F(void)" rather
than "int F()".)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */