#include <iostream> /* Basic design concept is that WorldObject implements remote method call functionality using the "curiously recurring template pattern" to enable forwarding calls from the generic base class that implements the transport layer to the derived class.
The specific failure was in forwarding calls to items in a container. This is emulated here by wrapping a single item. In the main program there are two forms of the call. In the last (uncommented) form the member function pointer is for clarity assigned to a variable (itemfunptr) before making the call. With 4.3.0 and 4.3.1 this code compiles incorrectly with -O1 or greater to produce this warning reproduce.cc: In function int main(): reproduce.cc:26: warning: itemfunptr.void (Container::*)(void (Item::*)(int), int)::__pfn is used uninitialized in this function reproduce.cc:47: note: itemfunptr.void (Container::*)(void (Item::*)(int), int)::__pfn was declared here and the resulting executable segvs. It works correctly with -O0. With 4.2.3 and earlier it works correctly with optimization. In the first (commented out) form of the call in the main program we directly refer to desired member function. This compiles and executes correctly with all tested versions. */ template <class Derived> struct WorldObject { template <typename memfunT, typename arg1T, typename arg2T> void forward(memfunT memfun, arg1T arg1, arg2T arg2) { Derived* obj = static_cast<Derived*>(this); (obj->*memfun)(arg1, arg2); } }; struct Item { void fred(int a) { std::cout << "a=" << a << std::endl; } }; struct Container : public WorldObject<Container> { Item item; template <typename itemfunT, typename arg1T> void itemfun(itemfunT itemfun, int a) { (item.*itemfun)(a); } }; int main() { typedef void (Item::*itemfun)(int); Container t; // This call compiles and executes correctly with all versions tested //t.forward(&Container::itemfun<itemfun,int>, &Item::fred, 1); // This call compiles with a warning and segvs on execution if using // -O1 or greater with 4.3.*. 4.2.* is correct. void (Container::*itemfunptr)(itemfun, int) = &Container::itemfun<itemfun,int>; t.forward(itemfunptr, &Item::fred, 1); return 0; } -- Summary: member function pointer failure with optimization Product: gcc Version: 4.3.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: rjharrison at gmail dot com GCC build triplet: x86_64-unknown-linux-gnu GCC host triplet: x86_64-unknown-linux-gnu GCC target triplet: x86_64-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37016