MIN and MAX in C

Where are MIN and MAX defined in C, if at all?

They arent.

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 wouldnt 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 GCCs 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, its no problem and a few months down the road, youll 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 of
typeof.

Its 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:

MIN and MAX in C

Theres a std::min and std::max in C++, but AFAIK, theres no equivalent in the C standard library. You can define them yourself with macros like

#define MAX(x, y) (((x) > (y)) ? (x) : (y))
#define MIN(x, y) (((x) < (y)) ? (x) : (y))

But this causes problems if you write something like MAX(++a, ++b).

MIN and MAX in C

MIN and MAX in C

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