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I've been doing a bit more C programming lately, and have come across a few features which surprised me.

Contents 1 Syntax 2 Types 2.1 char vs. unsigned char 2.2 size_t: int or long? 3 Standard Libraries 3.1 qsort 4 General ponderings 4.1 #include in what order? 5 Links/See also 5.1 Reading complicated C declarations

Syntax

Types

char vs. unsigned char

Don't forget that chars are signed, so anything bigger than 0x7F will appear negative unless it's typed as unsigned char

size_t: int or long?

On ia32, size_t is a 32bit unsigned int, on amd64, size_t is a 64bit unsigned int. Due to typedefery, this leads to (otherwise) perfectly good printf()s generating warnings when compiling on amd64 because "%i" doesn't apply size_t on amd64. Using "%li" for size_t should be fine.

Standard Libraries

qsort

qsort obviously will write to the data structure. This can lead to segfaults if a consted array is passed in (at least when using gcc 4.1.3 with the C99 standard).

General ponderings

#include in what order?

Should system includes come before or after local includes?

I.e., which is "better",

#include <stdio.h>
#include "mytool.h"

or

#include "mytool.h"
#include <stdio.h>

?

Links/See also

Reading complicated C declarations

• How To Read C Declarations