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Re: gcc and 'include'

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Michael S <already5chosen@yahoo.com> writes:

> On Fri, 27 Mar 2026 09:03:23 -0700
> Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:
>
>> Michael S <already5chosen@yahoo.com> writes:
>>
>>> On Thu, 26 Mar 2026 19:08:16 -0700
>>> Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:
>>>
>>>> Michael S <already5chosen@yahoo.com> writes:
>>>>
>>>>> On Thu, 26 Mar 2026 22:36:59 +0000
>>>>> Bart <bc@freeuk.com> 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?  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.
>>>>>>
>>>>>> [...]
>>>>>
>>>>> Sounds like a bug introduced during transition to c99/gnu99
>>>>> front end.
>>>>> With gcc4.x,  which defaults to gnu89 it still works.
>>>>> Also works with the latest gcc -std=gnu89
>>>>> But there is no hope that gcc maintaines will ever admit that it
>>>>> is a bug.
>>>>
>>>> It isn't a bug.  The C standard allows this behavior.
>>>
>>> So, by C standard, there is no situation in which 'inline'
>>> with no addition qualifuers like 'static' or 'extern' can be
>>> used with predictabe outcome?
>>
>> That depends on just how you mean the question.  If we have this
>> source file
>>
>>     inline int
>>     F(){
>>         return 0;
>>     }
>>
>>     int
>>     main(void){
>>         return F();
>>     }
>>
>> then we might get an undefined reference for F().  However if we
>> expand that source file just slightly, to
>>
>>     inline int
>>     F(){
>>         return 0;
>>     }
>>
>>     int
>>     main(void){
>>         return F();
>>     }
>>
>>     int F();
>>
>> then the program has well-defined behavior.  This result obtains
>> because the function F() now has a declaration that is (implicitly)
>> external, and without specifying 'inline', in addition to the
>> original inline definition.
>
> It is indeed well-defined.  But well-defined behavior does not
> match the most probable intention of programmer, which is to
> create a body of F() in case that it was not actually inlined and
> to *not* create it otherwise.

I simply disagree.  The behavior you describe is what people expect
for static inline functions.  It doesn't make sense that they would
expect the same thing for non-static inline functions, if they had
taken some time to think about it.

> For something like MSVC it does not matter, because by default it
> does not link unused functions into executive.  But something like
> gcc by default links everything in.

That depends on what you mean by "by default".  gcc does not
produce an actual function body for any optimization level
above -O0.  Surely the most common practice these days is to
enable some optimization level above -O0.

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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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