Finally FINALLY!

template<class F>
struct finally_helper
{
    F f;
    finally_helper(F &_f) : f(_f) {}
    ~finally_helper() { f(); }
};

#define CONCAT2(X,Y) X##Y
#define CONCAT(X,Y) CONCAT2(X,Y)

// gcc-4.5 chokes on this:
// #define FINALLY2(BODY,F,V) finally_helper<decltype( [&]()BODY )> V( [&]()BODY )
#define FINALLY2(BODY,F,V) auto F=[&]()BODY; finally_helper<decltype(F)> V(F)
#define FINALLY(BODY) FINALLY2(BODY,CONCAT(finally_fn,__LINE__),CONCAT(finally_var,__LINE__))

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int main(int argc,char **argv)
{

    void *b=malloc(1000);
    if (b) {
        FINALLY({
            printf("freeing b\n");
            free(b);
            b=0;
        });
        printf("working with b\n");
    }
    assert(b==0);
}