[Bug c/126702] undefined reference to inline function

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126702

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #7 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
> Therefore there is no choice; the compiler must use the only definition provided. Thus, the code above is valid C; it does not contain unspecified behavior, much less undefined behavior.

???

Annex J clearly states it's unspecified "whether a call to an inline function
uses the inline definition or the external definition
of the function (6.7.4)."

And the choice is valid for optimization: if the compiler is compiling a cold
code path it's a perfectly sensible choice to optimize it for size instead of
speed, so calling the function would be better than inlining a copy.  Here main
can be considered a cold path because in C main can only execute once (calling
main is undefined behavior).