[Bug c++/71024] New: Missing warning for contradictory attributes

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71024

            Bug ID: 71024
           Summary: Missing warning for contradictory attributes
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

Observe that on 

void __attribute ((always_inline)) foo (void);
void __attribute ((noinline)) foo (void);

$ ./cc1 -quiet q.cc 
q.cc:2:31: warning: declaration of ‘foo’ with attribute ‘noinline’ follows
declaration with attribute ‘always_inline’ [-Wattributes]
 void __attribute ((noinline)) foo (void);
                               ^~~
q.cc:1:36: note: previous declaration of ‘foo’ was here
 void __attribute ((always_inline)) foo (void);
                                    ^~~
but cc1plus is silent.  I think we need to factor out some code out of
diagnose_mismatched_decls.