Utility Macros

General useful language macros More...

Macros
#define	__build_assert(cond)    do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)
	Assert a build-time dependency.
#define	__build_assert_or_zero(cond)    (sizeof(char [1 - 2*!(cond)]) - 1)
	Assert a build-time dependency.
#define	__array_size(arr)   (sizeof(arr) / sizeof((arr)[0]) + _array_size_chk(arr))
	Get the number of elements in a visible array.
#define	_array_size_chk(arr)   0

Detailed Description

General useful language macros

This group contains definitions to help give robust solutions to common code patterns.

Macro Definition Documentation

__array_size

#define __array_size

(

arr

)

(sizeof(arr) / sizeof((arr)[0]) + _array_size_chk(arr))

Get the number of elements in a visible array.

This does not work on pointers, or arrays declared as [], or function parameters. With correct compiler support, such usage will cause a build error (

See also

__build_assert).

Parameters

arr	The array whose size you want.

__build_assert

#define __build_assert

(

cond

)

do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)

Assert a build-time dependency.

Your compiler will fail if the condition isn't true, or can't be evaluated by the compiler. This can only be used within a function.

Example:

#include <stddef.h>
...
static char *foo_to_char(struct foo *foo)
{
    // This code needs string to be at start of foo.
    __build_assert(offsetof(struct foo, string) == 0);
    return (char *)foo;
}

Parameters

cond	The compile-time condition which must be true.

See also

__build_assert_or_zero

__build_assert_or_zero

#define __build_assert_or_zero

(

cond

)

(sizeof(char [1 - 2*!(cond)]) - 1)

Assert a build-time dependency.

Your compiler will fail if the condition isn't true, or can't be evaluated by the compiler. This can be used in an expression: its value is "0".

Example:

#define foo_to_char(foo)                \
    ((char *)(foo)                      \
    + __build_assert_or_zero(offsetof(struct foo, string) == 0))

Parameters

cond	The compile-time condition which must be true.

See also

__build_assert

_array_size_chk

#define _array_size_chk

(

arr

)

0