Le 20/04/13 18:17, Olaf Peter a écrit :

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Is this intentionally or do I miss something?

Hi,

I see it breaks also code on msvc.

I'm running the regression test on my computer with the attached patch. Could you tell me if it works for you?

yes, it works. Committed revision 83988. Vicente

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namespace {

struct id_string { static boost::once_flag flag; typedef std::map map_type; ...

static void do_init(token_id_string& self) {

Mmh, wrong reduced/generalized even if I checked carefully, should be static void do_init(id_string& self) { insert(/* aka *this */self.m_map)(x, "y")(...) } But I see, you recognized this.

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insert(self.m_map)(x, "y")(...) ; }

std::string const& operator()(id::type id) const { boost::call_once(flag, &id_string::do_init, *this);

map_iterator s = m_map.find(id); ... } };

Hi,

the error /usr/local/include/boost/thread/detail/invoke.hpp:406:65: error: invalid initialization of non-const reference of type '{anonymous}::id_string&' from an rvalue of type '{anonymous}::id_string'

says you that the parameter (const) can not be used where a non-const is expected.

Shouldn't the operator be declared non-const

std::string const& operator()(id::type id) ;

The idea was to create a lazy lookup since this functor is only used on debugging, but compiled/linked at all build targets (I know, project structure ...). Imo making the member const/non-const is a taste of matter; const since it does primary a lookup, non-const due to the lazy initialization. So, I'm not sure.

In addition if you want to pass a reference you would need to use boost::ref().

The following compile well without the patch

struct id_string { static boost::once_flag flag; static void do_init(id_string & ) {} void operator()() { boost::call_once(flag, &id_string::do_init, boost::ref(*this)); } };

Note that the following compiles

struct id_string { static boost::once_flag flag; static void do_init(id_string & ) {} void operator()() { std::bind(&id_string::do_init, std::ref(*this))(); } void operator()(int) const { std::bind(&id_string::do_init, *this)(); } };

I would expect that the preceding fails as *this is a 'id_string const&' and do_init expects an 'id_string &'. This would explain why with the patch it worked as the patch was calling to std::bind.

But if make use of the class

{ id_string id; //id(); id(1); }

I get the following error

gcc.compile.c++ /tmp/bin.v2/boost/bin.v2/libs/thread/test/call_once_p.test/gcc-4.6.1.0x/debug/threading-multi/sync/mutual_exclusion/once/call_once/call_once_pass.o

In file included from /usr/include/c++/4.6/functional:56:0, from ../../../boost/thread/detail/invoke.hpp:34, from ../../../boost/thread/pthread/once_atomic.hpp:17, from ../../../boost/thread/once.hpp:20, from sync/mutual_exclusion/once/call_once/call_once_pass.cpp:26: /usr/include/c++/4.6/tuple: In constructor ‘constexpr std::_Head_base<_Idx, _Head, false>::_Head_base(const _Head&) [with unsigned int _Idx = 0u, _Head = id_string]’: /usr/include/c++/4.6/tuple:162:44: instantiated from ‘constexpr std::_Tuple_impl<_Idx, _Head, _Tail ...>::_Tuple_impl(const _Head&, const _Tail& ...) [with unsigned int _Idx = 0u, _Head = id_string, _Tail = {}]’ /usr/include/c++/4.6/tuple:423:24: instantiated from ‘constexpr std::tuple<_T1>::tuple(const _T1&) [with _T1 = id_string]’ /usr/include/c++/4.6/functional:1186:70: instantiated from ‘std::_Bind<_Functor(_Bound_args ...)>::_Bind(_Functor&&, _Args&& ...) [with _Args = {const id_string&}, _Functor = void (*)(id_string&), _Bound_args = {id_string}]’ /usr/include/c++/4.6/functional:1450:41: instantiated from ‘typename std::_Bind_helper<_Functor, _ArgTypes>::type std::bind(_Functor&&, _ArgTypes&& ...) [with _Functor = void (*)(id_string&), _ArgTypes = {const id_string&}, typename std::_Bind_helper<_Functor, _ArgTypes>::type = std::_Bind]’ sync/mutual_exclusion/once/call_once/call_once_pass.cpp:206:43: instantiated from here /usr/include/c++/4.6/tuple:97:25: erreur: use of deleted function ‘id_string::id_string(const id_string&)’ sync/mutual_exclusion/once/call_once/call_once_pass.cpp:194:8: erreur: ‘id_string::id_string(const id_string&)’ is implicitly deleted because the default definition would be ill-formed: sync/mutual_exclusion/once/call_once/call_once_pass.cpp:194:8: erreur: use of deleted function ‘boost::once_flag::once_flag(const boost::once_flag&)’ ../../../boost/thread/pthread/once_atomic.hpp:59:5: erreur: declared here

Could you tell me if works for you after rolling back the patch and adding the suggested changes on your code?

you mean using boost::ref? I'm not sure if I have std::ref on my old gcc compiler 4.6.3. Anyway, with thread/detail/invoke.hpp from Revision: 83985 std::string const& operator()(id::type id) { boost::call_once(flag, &id_string::do_init, boost::ref(*this)); map_iterator s = m_map.find(id); if (s == m_map.end()) { return m_map[id::invalid]; } else { return s->second; } ... } compiles, but not std::string const& operator()(id::type id) const, neither with ref or cref. Thanks, Olaf