Ensure macro to check preconditions

ensure.cpp

#include <iostream>

#define ENSURE(x) do { \
    if (not (x)) {std::cerr << __FILE__ << " " << __PRETTY_FUNCTION__ << ":" << __LINE__ << " " << #x << " assert failed!\n";} \
} while(false)

void f(int x)
{
    ENSURE(x > 0);
}

int main()
{
    f(10);
    f(-1); // print "ensure.cpp void f(int):9 x > 0 assert failed"
}