C++ template class inheritance and name looking up
1 #include <stdio.h>
2
3 template <int N>
4 struct Base {
5 int base[N];
6 Base() {
7 for (int i=0; i<N; ++i)
8 base[i] = i;
9 }
10 };
11
12 int base[1024];
13
14 template <int N>
15 struct Foo : public Base<N> {
16 void dump () {
17 for (int i=0; i<N; ++i)
18 printf ("%d ", base[i]);
19 printf ("\n");
20 }
21 };
22
23 int main (int argc, char **argv) {
24 Foo<10> foo;
25 foo.dump ();
26 }
The test CPP program gives different with SunStudio CC and g++.
g++: 0 0 0 0 0 0 0 0 0 0
sunstudio CC: 0 1 2 3 4 5 6 7 8 9
And, if we comment out line #12, i.e., the definition of ::base[], g++ would complain:
test.cpp: In member function `void Foo<N>::dump()':
test.cpp:18: error: `base' undeclared (first use this function)
It's a bug of g++? Actually, no, it's the correct behavior. Refer to the release note of gcc 3.4.
> In a template definition, unqualified names will no longer
find
> members of a dependent base (as specified by [temp.dep]/3
in
> the C++ standard).
