[Bug c++/62282] [4.8/4.9/5 Regression] Undefined reference with __inline __attribute(__gnu_inline__) with -O0

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62282

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
      Known to work|                            |4.2.4
         Resolution|INVALID                     |---
   Target Milestone|---                         |4.8.4
            Summary|Undefined reference with    |[4.8/4.9/5 Regression]
                   |__inline                    |Undefined reference with
                   |__attribute(__gnu_inline__) |__inline
                   |with -O0                    |__attribute(__gnu_inline__)
                   |                            |with -O0
      Known to fail|                            |4.3.6

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> Except it is not vague in general, the idea is that there is another
> definition somewhere of test and not just in this translation unit. Since we
> are at -O0, we decide not to inline it and it does not get emitted.

So with C++ 'inline __attribute__((__gnu_inline__))' is equivalent to
'extern inline __attribute__((__gnu_inline__))'?  What's the reason for
that?

It seems it is at least inconsistent with pre-c99 inline semantic?

G++ 4.1 links the test just fine (G++ 4.3 already shows the bad behavior),
but G++ 4.1 also links 'extern inline' fine (but it doesn't inline).

At least it's very old behavior it seeems, but a regression from G++ 4.2
which knows the attribute but correctly preserves the function(?).

Note that the C frontend happily links the testcase as well, preserving
the function.  That's an inconvenient difference between behavior of
C and C++ for an attribute that was introduced to provide backward
compatibility with pre-C99 inline semantics.