[ILUG] round and drand48

[David Malone]

I want to use both the c99 function round() and the drand48() function
in a single C program. To get the round() function on a recent
version of Ubuntu I need to give gcc the "--std=c99" flag, otherwise
I get the warnings:

	warning: incompatible implicit declaration of built-in function â

when I first use round.  This is bad, because round returns a double,
but the compiler will assume it returns an int.

If I do give this flag it then macros that tell glibc that I don't
want anything that isn't a C99 standard function, so then I get the
warning:

	warning: implicit declaration of function â

which is bad, because drand48 returns an double and the compiler
will think it returns an int.

I can think of two ways around this. First, I can explicitly give
my own declaration for drand48:

	extern double drand48(void);

but this is ugly 'cos I probably don't want to declare every function
that I might use. Slightly less ugly is that I can mess with glibc's
internal macros before including stdlib.h:

	#define __USE_XOPEN
	#include <stdlib.h>

This works, but I can't say I'm that happy with it. Does anyone
know what the blessed way of doing this on recent Linux/glibc/gcc
boxes is?

	David.