The following code gives this warning:

62 C:\Dev-Cpp\Projects\gcc-test\main.cpp
[Warning] unused variable 'x'

If you uncomment the constructor, the warning does not appear.

class Test
{
    public:        
    //Test() {}
};

int main(int argc, char *argv[])
{
	Test x;
	
  	return 0;
}

Happened on Windows 2000 SP4 with gcc-3.4.1-20040711-1, mingw-
runtime-3.3 and win32api-2.5.
Compiled with "-Wunused".