1 // PR c++/37016
2 // { dg-do run }
3 // { dg-options "-O2 -Wall" }
4
5 /*
6 Basic design concept is that WorldObject implements remote method call
7 functionality using the "curiously recurring template pattern" to enable
8 forwarding calls from the generic base class that implements the transport
9 layer to the derived class.
10
11 The specific failure was in forwarding calls to items in a container.
12 This is emulated here by wrapping a single item.
13
14 In the main program there are two forms of the call. In the last
15 (uncommented) form the member function pointer is for clarity
16 assigned to a variable (itemfunptr) before making the call.
17 With 4.3.0 and 4.3.1 this code compiles incorrectly with -O1 or greater
18 to produce this warning
19
20 reproduce.cc: In function ‘int main()’:
21 reproduce.cc:26: warning: ‘itemfunptr.void (Container::*)(void
22 (Item::*)(int), int)::__pfn’ is used uninitialized in this function
23 reproduce.cc:47: note: ‘itemfunptr.void (Container::*)(void (Item::*)(int),
24 int)::__pfn’ was declared here
25
26 and the resulting executable segvs. It works correctly with -O0.
27
28 With 4.2.3 and earlier it works correctly with optimization.
29
30 In the first (commented out) form of the call in the main program
31 we directly refer to desired member function. This compiles
32 and executes correctly with all tested versions.
33 */
34
35 extern "C" int printf (const char *, ...);
36
37 template <class Derived>
38 struct WorldObject {
39 template <typename memfunT, typename arg1T, typename arg2T>
forwardWorldObject40 void forward(memfunT memfun, arg1T arg1, arg2T arg2) {
41 Derived* obj = static_cast<Derived*>(this);
42 (obj->*memfun)(arg1, arg2);
43 }
44 };
45
46 struct Item {
fredItem47 void fred(int a) {
48 printf ("a=%d\n", a);
49 }
50 };
51
52 struct Container : public WorldObject<Container> {
53 Item item;
54 template <typename itemfunT, typename arg1T>
itemfunContainer55 void itemfun(itemfunT itemfun, int a) {
56 (item.*itemfun)(a);
57 }
58 };
59
main()60 int main() {
61 typedef void (Item::*itemfun)(int);
62
63 Container t;
64
65 // This call compiles and executes correctly with all versions tested
66 //t.forward(&Container::itemfun<itemfun,int>, &Item::fred, 1);
67
68 // This call compiles with a warning and segvs on execution if using
69 // -O1 or greater with 4.3.*. 4.2.* is correct.
70 void (Container::*itemfunptr)(itemfun, int) =
71 &Container::itemfun<itemfun,int>;
72 t.forward(itemfunptr, &Item::fred, 1);
73
74 return 0;
75 }
76
77