/// main.cc
template<class T> struct Foo
{
    Foo() __attribute__((always_inline));
};

template<class T> Foo<T>::Foo() {}

void bar()
{
    Foo<int> foo;
}

//////

$ g++ -v
Reading specs from .../gcc/3.4.0/bin/../lib/gcc/i686-pc-linux-gnu/3.4.0/specs
Configured with: ../gcc-3.4.0/configure --prefix=.../gcc/3.4.0
Thread model: posix
gcc version 3.4.0

$ g++ -c -o main.o main.cc
main.cc: In function `void bar()':
main.cc:6: sorry, unimplemented: inlining failed in call to 'Foo<T>::Foo() 
[with T = int]': function body not available
main.cc:10: sorry, unimplemented: called from here

The error message points at the function body (line 6) and says that it is not 
available.

GCC 3.3.3 is able to inline the call.