[Bug c++/82594] Please provide better parameter / argument mismatch warnings/notes

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82594

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-10-17
            Version|unknown                     |7.2.0
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So if there are more than one overloads, the C++ front-end produces:
t88.c: In function 'void initialize()':
t88.c:13:35: error: no matching function for call to 'set_delete_thread(void
(&)(S2*))'
   set_delete_thread (delete_thread);
                                   ^
t88.c:5:6: note: candidate: void set_delete_thread(S1*, void (*)(S2*))
 void set_delete_thread (struct S1 *, void (*) (struct S2 *));
      ^~~~~~~~~~~~~~~~~
t88.c:5:6: note:   candidate expects 2 arguments, 1 provided
t88.c:6:6: note: candidate: void set_delete_thread(S1*)
 void set_delete_thread (struct S1 *);
      ^~~~~~~~~~~~~~~~~
t88.c:6:6: note:   no known conversion for argument 1 from 'void(S2*)' to 'S1*'


But with only one overload, GCC produces:
t88.c: In function 'void initialize()':
t88.c:13:35: error: cannot convert 'void (*)(S2*)' to 'S1*' for argument '1' to
'void set_delete_thread(S1*, void (*)(S2*))'
   set_delete_thread (delete_thread);
                                   ^


I do think the C++ front-end's case with one overload set is actually can be
improved.

Note the C front-end produces:
t88.c: In function 'initialize':
t88.c:13:22: warning: passing argument 1 of 'set_delete_thread' from
incompatible pointer type [-Wincompatible-pointer-types]
   set_delete_thread (delete_thread);
                      ^~~~~~~~~~~~~
t88.c:5:6: note: expected 'struct S1 *' but argument is of type 'void
(*)(struct S2 *)'
 void set_delete_thread (struct S1 *, void (*) (struct S2 *));
      ^~~~~~~~~~~~~~~~~
t88.c:13:3: error: too few arguments to function 'set_delete_thread'
   set_delete_thread (delete_thread);
   ^~~~~~~~~~~~~~~~~
t88.c:5:6: note: declared here
 void set_delete_thread (struct S1 *, void (*) (struct S2 *));
      ^~~~~~~~~~~~~~~~~