id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
9134	"Code that uses BOOST_THROW_EXCEPTION produces a lot of ""result may be used uninitialized (...)"" warnings in certain conditions"	Adam Romanek <romanek.adam@…>	Emil Dotchevski	"The problem appears when using g++ with `-Wuninitialized -fno-exceptions -O3` flags.

Given a simple test:
{{{
#include <boost/lexical_cast.hpp>

int main() {
  return boost::lexical_cast<int>("""");
}
}}}

when compiled using g++ v4.6.3 produces the following output:
{{{
$ g++ test.cpp -Iboost -fno-exceptions -Wuninitialized -O3 -c

In file included from test.cpp:1:0:
boost/boost/lexical_cast.hpp: In static member function ‘static Target boost::detail::lexical_cast_do_cast<Target, Source>::lexical_cast_impl(const Source&) [with Target = int, Source = const char*]’:
boost/boost/lexical_cast.hpp:2353:24: warning: ‘result’ may be used uninitialized in this function [-Wuninitialized]
}}}

Please note that this problem appears only when using `-O3` optimization level.

One way of fixing this issue is to add `BOOST_ATTRIBUTE_NORETURN` to `boost::throw_exception()` declaration in `boost/throw_exception.hpp`, as shown in the attached patch.

It should be safe to do so, as the documentation of `boost::throw_exception()` says that:

> (...) Callers of throw_exception are allowed to assume that the function never returns (...)

This solves the issue completely."	Patches	new	To Be Determined	exception	Boost 1.54.0	Problem