Re: Numeric constants as strings

From: Mark Wooding <mdw@distorted.org.uk>
Date: Feb 19, 2007, 10:04 UTC
Message-ID: <slrnetitgs.sbe.mdw@metalzone.distorted.org.uk>
In-Reply-To: <200702190916.35813.andyparkins@gmail.com>

Andy Parkins <andyparkins@gmail.com> wrote:

Show 6 quoted lines

> I'm working on bringing my hash width literals patch up to date now
> that 1.5.0 has passed.  It's all been trivial apart from one line:
>
> #define HASH_WIDTH_ASCII 40
> -               printf("%-40s %s%s (%d subtrees)\n",
> +               printf("%-" HASH_WIDTH_ASCII "s %s%s (%d subtrees)\n",

The standard two-step goes

#define STRINGIFY(foo) STRINGIFY_REALLY(foo) #define STRINGIFY_REALLY(foo) #foo

The purpose of STRINGIFY_REALLY is to macro-expand the argument foo. If you just invoked STRINGIFY_REALLY

  printf("%-" STRINGIFY_REALLY(HASH_WIDTH_ASCII) "s %s%s (%d subtrees)\n",

you'd get

  printf("%-HASH_WIDTH_ASCIIs %s%s (%d subtrees)\n", ...

which is not what you wanted.  However,

  printf("%-" STRINGIFY(HASH_WIDTH_ASCII) "s %s%s (%d subtrees)\n",

will do the right thing.

-- [mdw]