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Groups > comp.lang.c > #397244
| From | Tim Rentsch <tr.17687@z991.linuxsc.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: gcc and 'include' |
| Date | 2026-03-28 00:30 -0700 |
| Organization | A noiseless patient Spider |
| Message-ID | <86fr5k2yyg.fsf@linuxsc.com> (permalink) |
| References | <10q4ceb$38i2d$1@dont-email.me> <10q7pgg$bju3$1@dont-email.me> |
Andrey Tarasevich <noone@noone.net> writes:
> On Thu 3/26/2026 3:36 PM, Bart wrote:
>
>> 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?
>
> Yes.
>
> C is very different from C++ when it comes to inline functions with
> external linkage. The language stoically sticks to "manual ODR"
> philosophy and refuses to employ the "common section" approach used by
> C++. C will not automatically emit an out-of-line definition for an
> external-linkage inline function. It is your responsibility to provide
> one (and choose the site for one) by making an `extern inline`
> declaration.
>
> If the compiler decides not to inline the call, it will seek an
> out-of-line "body" for your function. If there's no out-of-line
> "body", you will get a linker error. Which is exactly what happened in
> your case.
>
> So, you have to choose a site for the out-of-line definition - one and
> only one translation unit, in which you have to declare your function
> as `extern inline`. This translation unit will host the out-of-line
> "body" for the function. Since in your case you have only one
> translation unit, you can do it as
>
> inline int F(){return rand();}
> extern inline int F(); /* <- emits an out-of-line definition */
Note that both 'extern' and 'inline' here can be dispensed with
on the declaration. Rather than 'extern inline int F();' it
suffices to say
int F();
to force the compiler to produce a real function body with
a linker-visible symbol. And doing that doesn't interfere
with the function being an inline function.
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar
gcc and 'include' Bart <bc@freeuk.com> - 2026-03-26 22:36 +0000
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-26 16:12 -0700
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 10:55 +0000
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 13:49 +0100
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-27 10:51 -0700
Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-27 21:27 +0000
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 22:05 +0000
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-27 17:03 -0700
Re: gcc and 'include' Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-03-28 05:10 +0100
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-28 20:37 +0300
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-28 18:33 +0000
Re: gcc and 'include' antispam@fricas.org (Waldek Hebisch) - 2026-03-29 00:53 +0000
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-29 22:37 +0100
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 05:33 -0700
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 14:42 +0100
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-30 16:53 +0300
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 18:11 +0100
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 08:27 -0700
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-30 11:54 -0700
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 21:54 +0100
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-30 18:07 -0700
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-31 11:39 +0100
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-31 13:56 -0700
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-06 20:56 -0700
Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-04-06 23:12 -0700
Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-30 21:06 -0400
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-29 11:24 +0200
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-29 12:44 +0100
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-31 15:57 +0200
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 07:20 -0700
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 05:07 -0700
Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-27 00:25 +0000
Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 07:13 +0000
Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-30 07:54 -0700
Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-31 01:46 +0000
Re: gcc and 'include' antispam@fricas.org (Waldek Hebisch) - 2026-03-31 05:28 +0000
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-27 04:10 +0300
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-26 19:08 -0700
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-27 16:47 +0300
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 16:43 +0100
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-27 09:03 -0700
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 11:46 +0300
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 08:19 -0700
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-30 20:08 +0300
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-31 00:26 -0700
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-31 11:27 +0300
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-07 09:45 -0700
Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-28 10:25 -0700
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 10:37 +0300
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-29 11:30 +0200
Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-29 07:22 -0700
Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-29 13:56 -0400
Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 21:39 +0300
Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-29 20:08 -0400
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 01:58 +0100
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 07:59 -0700
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-26 19:06 -0700
Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 16:20 +0000
Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 18:07 +0100
Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-28 18:48 -0400
Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-27 22:38 -0700
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-28 00:30 -0700
Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-29 16:15 -0700
Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 00:41 -0700
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