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Allow using noexcept methods with event tables macros

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Explicitly remove noexcept before static-casting the member function
pointer to the base class pointer type to avoid compilation error with
C++17.

Add a test checking that this does work now.

Closes #18721.
This commit is contained in:
Vadim Zeitlin 2020-04-09 19:48:59 +02:00
parent f4f70102ea
commit c3810da549
2 changed files with 42 additions and 1 deletions
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36
include/wx/event.h
View File

@ -144,9 +144,43 @@ inline wxEventFunction wxEventFunctionCast(void (wxEvtHandler::*func)(T&))
wxGCC_WARNING_RESTORE_CAST_FUNCTION_TYPE()
}
// Special hack to remove "noexcept" from the function type when using C++17 or
// later: static_cast<> below would fail to cast a member function pointer to a
// member of a derived class to the base class if noexcept is specified for the
// former, so remove it first if necessary.
#if __cplusplus >= 201703L
namespace wxPrivate
{
// Generic template version, doing nothing.
template <typename T>
struct RemoveNoexceptEventHandler
{
using type = T;
};
// Specialization removing noexcept when it's specified.
//
// Note that this doesn't pretend to be generally suitable, this is just enough
// to work in our particular case.
template <typename R, typename C, typename E>
struct RemoveNoexceptEventHandler<R (C::*)(E&) noexcept>
{
using type = R (C::*)(E&);
};
} // namespace wxPrivate
#define wxREMOVE_NOEXCEPT_EVENT_HANDLER(pmf) \
static_cast<wxPrivate::RemoveNoexceptEventHandler<decltype(pmf)>::type>(pmf)
#else
#define wxREMOVE_NOEXCEPT_EVENT_HANDLER(pmf) pmf
#endif
// Try to cast the given event handler to the correct handler type:
#define wxEVENT_HANDLER_CAST( functype, func ) \
wxEventFunctionCast(static_cast<functype>(&func))
wxEventFunctionCast(static_cast<functype>(wxREMOVE_NOEXCEPT_EVENT_HANDLER(&func)))
// The tag is a type associated to the event type (which is an integer itself,

7
tests/events/evthandler.cpp
View File

@ -122,6 +122,9 @@ public:
void OnEvent(wxEvent&) { g_called.method = true; }
void OnAnotherEvent(AnotherEvent&);
void OnIdle(wxIdleEvent&) { g_called.method = true; }
#ifdef wxHAS_NOEXCEPT
void OnIdleNoExcept(wxIdleEvent&) noexcept { }
#endif
private:
wxDECLARE_EVENT_TABLE();
@ -138,6 +141,10 @@ wxBEGIN_EVENT_TABLE(MyClassWithEventTable, wxEvtHandler)
EVT_MYEVENT(MyClassWithEventTable::OnMyEvent)
EVT_MYEVENT(MyClassWithEventTable::OnEvent)
#ifdef wxHAS_NOEXCEPT
EVT_IDLE(MyClassWithEventTable::OnIdleNoExcept)
#endif
// this shouldn't compile:
//EVT_MYEVENT(MyClassWithEventTable::OnIdle)
//EVT_IDLE(MyClassWithEventTable::OnAnotherEvent)