Re: [boost] [utility]result_of - erroneous result type from a C++11 lambda

Subject: Re: [boost] [utility]result_of - erroneous result type from a C++11 lambda
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2013-04-02 13:35:23

On Tuesday 02 April 2013 19:16:21 Vicente J. Botet Escriba wrote:
> Hi,
> 
> I've started to use C++11 lambda functions with Boost.Thread.
> 
> The following works with clang-3.2
> 
> boost::future<int> f1 = boost::async( []() -> int {return 123;} );
> 
> 
> But it fails with gcc-4.6.2, 4.7.2 and 4.8.0
> 
> ../example/lambda_future.cpp:25:91: erreur: conversion from
> ‘boost::future<void>’ to non-scalar type ‘boost::future<int>’ requested
> boost::future<int> f1 = boost::async( []() -> int {return 123;} );
> 
> The current implementation of boost::async uses boost::result_of to get
> the result type of the callable parameter.
> 
> Is this a know bug on boost::result_of or gcc compiler?

I think this is because result_of is based on decltype for clang and TR1 
protocol for gcc. This is because gcc doesn't support N3276. 4.8.0 release 
notes state that it is supported but I saw someone on the list found some bug 
in it so the support is incomplete for now.