[Boost-users] signals2::slot_type & g++ anti-aliasing warning

Subject: [Boost-users] signals2::slot_type & g++ anti-aliasing warning
From: Ákos Maróy (akos_at_[hidden])
Date: 2010-11-08 03:44:41

Hi,

I bumped into an issue, where g++ would give me an anti-aliasing warning
for very basic / straightforward signals2 code. consider the following
sample code:

#include <iostream>

#include <boost/bind.hpp>
#include <boost/signals2.hpp>

typedef boost::signals2::signal<void (void)>  sig_t;

void ff(void) {
    std::cout << "ff" << std::endl;
}

int main(void) {
    sig_t::slot_type ss = boost::bind(&ff);

    return 0;
}

when compiled with the -Wall and -O2 flags, I get the following compiler
warning:

...
sample.cxx:13:   instantiated from here
/home/maroy/src/mxp/usr/include/boost/function/function_base.hpp:321:
warning: dereferencing type-punned pointer will break strict-aliasing rules
/home/maroy/src/mxp/usr/include/boost/function/function_base.hpp:325:
warning: dereferencing type-punned pointer will break strict-aliasing rules

(I can provide the full compiler output if needed)

this is with boost 1.44 on a linux x86_64, g++ version 4.4.3

omitting either the -O2 or the -Wall flags will make the warning go away.

what am I doing wrong?

Akos