On 6/13/06, Gavin Band <[EMAIL PROTECTED]> wrote:
Hello,
I hope this is the right place for this sort of question, which concerns
the behaviour of gcc (versions 3.4.4 and 4.1.1) and template
specialisations.
I have some code split into three files header.hpp, specialisation.cpp,
and main.cpp, given below. A class having a template member function
print() is defined in "header.hpp", and a specialisation of print() for
std::strings is defined in "specialisation.cpp". In "main.cpp" print()
is used to print an integer and then a string.
Without any optimisation turned on (i.e. compiling with the command line
"g++ -o test test.cpp specialisation.cpp")
the program output is
$ ./main
The object of type T was: 256.
The string was: hello.
If I compile with -O3, however, I get
$ ./main
The object of type T was: 256.
The object of type T was: hello.
Let me call the former behaviour "good" and the latter "bad" - here are
the optimisation flags which cause "good" and "bad" behaviour on my
machine:
gcc 3.4.4: good: -O0, -O1 bad: -O2 or greater.
gcc 4.1.1: good: -O0 bad: -O1 or greater
But perhaps it is not gcc but rather my code that is at fault? This is
on a Linux box. The code is below.
#include <iostream>
#include <string>
#include "header.hpp"
int main(int argc, char** argv)
{
std::string s("hello");
int i(256);
A a;
a.print(std::cerr, i);
a.print(std::cerr, s);
return 0;
}
You need to make a specialization declaration visible to main(), otherwise
gcc will inline the not specialized version at -O and above.
Richard.
