Where are
MINandMAXdefined in C, if at all?
They aren't.
What is the best way to implement these, as generically and type safe as possible (compiler extensions/builtins for mainstream compilers preferred).
As functions. I wouldn't use macros like #define MIN(X, Y) (((X) < (Y)) ? (X) : (Y)), especially if you plan to deploy your code. Either write your own, use something like standard fmax or fmin, or fix the macro using GCC's typeof (you get typesafety bonus too) in a GCC statement expression:
#define max(a,b) \
({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a > _b ? _a : _b; })
Everyone says "oh I know about double evaluation, it's no problem" and a few months down the road, you'll be debugging the silliest problems for hours on end.
Note the use of __typeof__ instead of typeof:
Answer from David Titarenco on Stack OverflowIf you are writing a header file that must work when included in ISO C programs, write
__typeof__instead oftypeof.
Where are
MINandMAXdefined in C, if at all?
They aren't.
What is the best way to implement these, as generically and type safe as possible (compiler extensions/builtins for mainstream compilers preferred).
As functions. I wouldn't use macros like #define MIN(X, Y) (((X) < (Y)) ? (X) : (Y)), especially if you plan to deploy your code. Either write your own, use something like standard fmax or fmin, or fix the macro using GCC's typeof (you get typesafety bonus too) in a GCC statement expression:
#define max(a,b) \
({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a > _b ? _a : _b; })
Everyone says "oh I know about double evaluation, it's no problem" and a few months down the road, you'll be debugging the silliest problems for hours on end.
Note the use of __typeof__ instead of typeof:
If you are writing a header file that must work when included in ISO C programs, write
__typeof__instead oftypeof.
It's also provided in the GNU libc (Linux) and FreeBSD versions of sys/param.h, and has the definition provided by dreamlax.
On Debian:
$ uname -sr
Linux 2.6.11
$ cat /etc/debian_version
5.0.2
$ egrep 'MIN\(|MAX\(' /usr/include/sys/param.h
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
$ head -n 2 /usr/include/sys/param.h | grep GNU
This file is part of the GNU C Library.
On FreeBSD:
$ uname -sr
FreeBSD 5.5-STABLE
$ egrep 'MIN\(|MAX\(' /usr/include/sys/param.h
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
The source repositories are here:
- GNU C Library
- FreeBSD
Videos
Sorry for the newbie question, I'm looking for a way to find the maximum between two values in C and I stumbled upon this, which make it sound like max() is a macro defined in stdlib.h, however when I look up the file I can't find it, and when I try to compile the example I get an 'implicit declaration' warning then an 'undefined reference' at execution.
That stackoverflow discussion seems to go that way and suggests that one uses fmax from the math library, or write the max() themselves.
I don't know if I'm just bad at reading documentation or if there's actually something special about that I should know about. Either way if someone can help me figuring this out, i'd be grateful.
(PS : it's for a school project where I won't have any issues with double evaluation so a dirty solution will do)