[Bug middle-end/63220] error: inlining failed in call to always_inline

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63220

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
First of all you should mark the functions 'inline' as well.  Then the issue
is that 'eq' is called indirectly which isn't allowed for always_inline
functions:

t.C:81:66: error: inlining failed in call to always_inline 'static constexpr
bool std::__1::char_traits<char>::eq(std::__1::char_traits<char>::char_type,
std::__1::char_traits<char>::char_type)': indirect function call with a yet
undetermined callee
       __attribute__ (( __always_inline__)) static constexpr bool eq(char_type
__c1, char_type __c2)  {
                                                                  ^
t.C:75:37: error: called from here
             if (!__pred(*__m1, *__m2)) { } 
                                     ^

which means this is a missed-optimization only.  The error is your fault.

Note that getting the error is unreliable so -O0 simply doesn't discover the
failed inlining.