gistfile1.txt

$ echo "++HEADER";cat test.h; echo "++IMPL"; cat test.cpp;(CXXFLAGS=--std=c++11 make test && ./test)
++HEADER
#ifndef _TEST_H_
#define _TEST_H_
class foo {
public: foo(int a=1);
};
#endif
++IMPL
#include "test.h"
#include <iostream>

foo::foo(int a/*=1*/) {
	std::cout << a << std::endl;
}


int main(int argc, char** argv) {
	foo();
	foo(2);
	return 0;
}
g++ --std=c++11    test.cpp   -o test
1
2