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Guest
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 Posted: Tue Sep 12, 2006 11:24 pm Post subject: Question on template argument deduction. |
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Hello. The both code snippets below compile fine on GCC but the second
one fails on Comeau Compiler.
// #1
template <typename T> void g(T) {}
template <typename T> void f(T, void (*)(T)) { }
int main()
{
f<int>(1, g);
}
------------------------------------------------
// #2
template <typename T> void g(T) {}
template <typename T> void f(T, void (*)(T)) {}
int main()
{
f(1, g);
}
Which compiler is right and why?
Thanks in advance.
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Greg Herlihy
Guest
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| Posted: Wed Sep 13, 2006 8:50 am Post subject: Re: Question on template argument deduction. |
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kiryazev (AT) gmail (DOT) com wrote:
| Quote: | Hello. The both code snippets below compile fine on GCC but the second
one fails on Comeau Compiler.
// #1
template <typename T> void g(T) {}
template <typename T> void f(T, void (*)(T)) { }
int main()
{
f<int>(1, g);
}
------------------------------------------------
// #2
template <typename T> void g(T) {}
template <typename T> void f(T, void (*)(T)) {}
int main()
{
f(1, g);
}
Which compiler is right and why?
|
I would say that the Comeau compiler is correct and that the parameter
types of the function call f() cannot be deduced according to the rules
of C++.
The simple explanation is that each parameter's type in the call to f()
must first be deduced independently of the others. There is therefore
simply no way to deduce the type of function pointer g represents
because g is itself a function template which could be instantiated
with any type.
Greg
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