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Type problem with template functions and inheritance ?
- From: Simon MARTIN <simartin at users dot sourceforge dot net>
- To: gcc at gcc dot gnu dot org
- Date: Wed, 8 Sep 2004 22:11:28 +0200
- Subject: Type problem with template functions and inheritance ?
Hello.
I played a little with templates and template functions, and I encountered a
problem with GCC while doing so. The code at the end of this message builds
with Microsoft's Visual C++ Toolkit 2003, but fails with GCC. Since the code
is quite "weird", I wonder whether there's a problem in GCC or Visual is too
laxist.
What is strange is:
- the "<unknown type>" in the error message
- the fact that if I "help" GCC a little (before the first static_cast),
then things work fine.
Thanks in advance for your help / explanation.
Regards,
Simon
[simon@texel gcc_test]$ g++ -v
Reading specs from /usr/lib/gcc-lib/i586-mandrake-linux-gnu/3.3.2/specs
Configured with: ../configure --prefix=/usr --libdir=/usr/lib
--with-slibdir=/lib --mandir=/usr/share/man --infodir=/usr/share/info
--enable-shared --enable-threads=posix --disable-checking --enable-long-long
--enable-__cxa_atexit --enable-clocale=gnu
--enable-languages=c,c++,ada,f77,objc,java,pascal
--host=i586-mandrake-linux-gnu --with-system-zlib
Thread model: posix
gcc version 3.3.2 (Mandrake Linux 10.0 3.3.2-6mdk)
[simon@texel gcc_test]$ g++ -Wall -o test test.cpp
test.cpp: In function `int main(int, char**)':
test.cpp:18: error: invalid static_cast from type `<unknown type>' to type
`bool (Base::*)(const char*)'
==== test.cpp
class Base {};
struct MyClass : public Base
{
template<int key> bool Method(const char *value) { return true; }
};
int main(int argc, char *argv[])
{
typedef bool (Base::*BaseMethodPtr)(const char*);
typedef bool (MyClass::*MethodPtr)(const char*);
MyClass aClass;
MethodPtr mp = &MyClass::Method<1>;
BaseMethodPtr p1 = static_cast<BaseMethodPtr>(mp);
(aClass.*p1)("One");
BaseMethodPtr p2 = static_cast<BaseMethodPtr>(&MyClass::Method<1>);
(aClass.*p2)("OneAgain");
return 0;
}
==== end of test.cpp
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