http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52888
Bug #: 52888
Summary: Unable to inline function pointer call with inexact
signature match
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: rtl-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: msha...@users.sourceforge.net
#include <stdio.h>
struct A {
template <typename T>
static inline __attribute__((always_inline))
void Caller (T* pn, void (T::*pm)(void))
{ (pn->*pm)(); }
void Call (int i) {
if (i == 1) Caller(this, &A::Func1);
else if (i == 2) Caller(this, &A::Func2);
}
inline void Func1 (void) { puts ("Func1"); }
inline void Func2 (void) noexcept { puts ("Func2"); }
};
int main (void) { A a; a.Call(1); a.Call(2); return (0); }
-------------------------------------------------------------
Compiling with: g++ (GCC) 4.7.0 20120324 (prerelease), x86_64
> g++ -O -std=c++11 a.cc
a.cc: In function 'int main()':
a.cc:5:55: error: inlining failed in call to always_inline 'static void
A::Caller(T*, void (T::*)()) [with T = A]': mismatched arguments
a.cc:10:42: error: called from here
a.cc:5:55: error: inlining failed in call to always_inline 'static void
A::Caller(T*, void (T::*)()) [with T = A]': mismatched arguments
a.cc:10:42: error: called from here
-------------------------------------------------------------
I'm using always_inline to force the error; without it Caller is not inlined
errorlessly.
The problem occurs when the function pointer has an inexact signature match to
the pointed function. In the above example, Func2 has a noexcept tacked on to
it. In more complex examples involving pointer to function with arguments,
using a typedef of an object in argument list results in this error, while
using the actual object works (typedef A a_t; void good(A&); void bad(a_t&)).
So the compiler is able to explicitly convert an inexact match like &A::Func2
to void(A::*)(void) when instantiating the template, but the inliner is not
able to make the same match even though it should have the same information.
