[Bug target/102953] Improvements to CET-IBT and ENDBR generation

[andrew.cooper3 at citrix dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102953

--- Comment #8 from Andrew Cooper <andrew.cooper3 at citrix dot com> ---
Actually, there is a (possibly pre-existing) diagnostics issue:

$ cat proto.c
static void __attribute__((cf_check)) foo(void);
static void __attribute__((unused)) foo(void)
{
}
void (*ptr)(void) = foo;

$ gcc -Wall -Os -fcf-protection=branch -mmanual-endbr -fcf-check-attribute=no
-c proto.c -o proto.o
proto.c:2:37: error: conflicting types for 'foo'; have 'void(void)'
    2 | static void __attribute__((unused)) foo(void)
      |                                     ^~~
proto.c:1:39: note: previous declaration of 'foo' with type 'void(void)'
    1 | static void __attribute__((cf_check)) foo(void);
      |                                       ^~~


The diagnostic complaining that the forward declaration doesn't match the
definition gives 'void(void)' as the type in both cases, leaving out the fact
that they differ by cf_check-ness.