Is this N_TIMES loop macro safe for all arguments?

[Alf P. Steinbach]

My original N_TIMES macro, called $n_times, used a range based `for`
loop. But g++ warned about the loop control variable being unused, and I
found no way to shut it up in code (only way was to turn off that
warning in the g++ invocation). So I'm thinking of using this scheme:


#include <iostream>
#include <stddef.h>
using namespace std;

using Size = ptrdiff_t;
using Index = Size;

#define MM_CONCAT__( a, b ) a ## b
#define MM_CONCAT_( a, b ) MM_CONCAT__( a, b )
#define MM_CONCAT( a, b ) MM_CONCAT_( a, b )

#define N_TIMES_AUX( i, n, expr ) Index i = 0, n = expr; i < n; ++i
#define N_TIMES( n ) N_TIMES_AUX( MM_CONCAT( i_, __COUNTER__ ),
MM_CONCAT( i_, __COUNTER__ ), n )

auto main() -> int
{
int const n = 7;
for( N_TIMES( n ) )
{
cout << "! ";
}
cout << endl;
}


Here __COUNTER__ is a language extension supported by Visual C++, g++
and clang, and probably far more compilers. Along with the other
language extensions I use (#pragma once, #pragma push, #pragma pop, $ in
identifiers) it's widely supported but not standard, while all sorts of
never-seen-in-the-wild things are being standardized. Hrmf. Innovating
committee. I aim just for the supporting compilers.

Anyway, even though I just wrote this code, and e.g. applied the
concatenation trick out of some acquired instinct for that, I don't
understand the details of how it avoids the actual macro argument `n`,
given in `main`, being replaced with the value of the formal macro
argument `n` i N_TIMES_AUX. It works but I don't know how...

So, my attempt at breaking it failed, which I'm happy about. Also, that
I identified a big hole in my understanding, that I could ask about. But
is there still some way to break this code?


Cheers!

- Alf

[Mr Flibble]

Why do you insist on obfuscating your C++ code with all these fucktarded
macros? You need to relearn writing C++ code without the use of macros.

/Flibble