[Bug c/70665] New: Seemingly incorrect warning for being const correct with function pointers

[psusi at ubuntu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70665

Bug ID: 70665
   Summary: Seemingly incorrect warning for being const correct
with function pointers
   Product: gcc
   Version: 4.8.2
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c
  Assignee: unassigned at gcc dot gnu.org
  Reporter: psusi at ubuntu dot com
  Target Milestone: ---

void foo( const char *p );
void bar( char *p ) { foo( p ); }

This is perfectly acceptable and const correct since foo does not want write
access, but being given write access anyway is fine.  I have run into a
seemingly incorrect warning though when calling such functions via pointer:

void foo( const char *p );
void bar( void (*fn)(char *p) );

bar( foo );

^^ generates warning about pointers not being compatible.

Apparently gcc thinks that when called via a pointer, it is not correct to pass
a writable pointer where only a read only one is needed.

[Bug c/70665] Seemingly incorrect warning for being const correct with function pointers

[psusi at ubuntu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70665

--- Comment #2 from Phillipi Susi  ---
Yes, so why is there an implicit conversion that does not cause a warning when
called directly, but not when called via pointer?