__SHORT_FILE__ Macro

short_file.cpp

#include <stdio.h>

using cstr = const char * const;
static cstr constexpr past_last_slash(cstr str, cstr last_slash)
{
    return
        *str == '\0' ? last_slash :
        *str == '/'  ? past_last_slash(str + 1, str + 1)
                     : past_last_slash(str + 1, last_slash);
}

static cstr constexpr past_last_slash(cstr str) { return past_last_slash(str, str); }

#define __SHORT_FILE__ ({constexpr cstr sf__ {past_last_slash(__FILE__)}; sf__;})

int main()
{
    puts(__SHORT_FILE__);
    return 0;
}

thanks a lot!

btw, I noticed that constexpr functions allow loops as well. so the recursion can be avoided easily:

static constexpr const char* past_last_slash_loop(const char * const str)
{
  const char* last_slash = str;
  for (const char* pos = str; *pos != 0x0; ++pos) {
    if (*pos == '/')
      last_slash = pos + 1;
  }
  return last_slash;
}

this should(tm) speedup compilation in larger projects. or?

Hey @mbehr1, you are right with loops being allowed since C++14 i think, but this piece of code was designed to be run on c++11 compilers also. I don't think that loop vs. recursion (this is easily tail-recursionable) is a speed difference, but i also did not measure it. I guess it remains a matter of taste.

ah. right. that's c++14 only. and yes, more a matter of style