Which, if any, C++ compilers do tail-recursion optimization?

Question

It seems to me that it would work perfectly well to do tail-recursion optimization in both C and C++, yet while debugging I never seem to see a frame stack that indicates th

Answer 1

All current mainstream compilers perform tail call optimisation fairly well (and have done for more than a decade), even for mutually recursive calls such as:

int bar(int, int);

int foo(int n, int acc) {
    return (n == 0) ? acc : bar(n - 1, acc + 2);
}

int bar(int n, int acc) {
    return (n == 0) ? acc : foo(n - 1, acc + 1);
}

Letting the compiler do the optimisation is straightforward: Just switch on optimisation for speed:

• For MSVC, use /O2 or /Ox.
• For GCC, Clang and ICC, use -O3

An easy way to check if the compiler did the optimisation is to perform a call that would otherwise result in a stack overflow — or looking at the assembly output.

As an interesting historical note, tail call optimisation for C was added to the GCC in the course of a diploma thesis by Mark Probst. The thesis describes some interesting caveats in the implementation. It's worth reading.