Abi tests/Helper macros for char signedness

[matu3ba]

As of now, char, which is de facto used in string.h has no abi tests for the user.

Macros for usage

// MACROS
#define IS_SIGNED(Type) (((Type)-1) < 0)

#include <assert.h>
static_assert(sizeof(U8) == 1, "U8 must have 1 byte size"); // compile-time error

// http://scaryreasoner.wordpress.com/2009/02/28/checking-sizeof-at-compile-time/
#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
usage: BUILD_BUG_ON( sizeof(someThing) != PAGE_SIZE );

The macros themself are also useful for a quick abi tests and providing one header+main.c example (ie under 0BSD) would be nice.

[matu3ba]

Please let me know, what you think would be useful to use as "assumption of this testing framework" and "user-configurations of this testing framework".

#ifndef __cplusplus // disable clang complains
#include <stdint.h> // abi: uint32_t, uint8_t
#include <stdlib.h> // assert: exit
#include <stdio.h>  // assert: fprintf

#ifdef TRUE
#error "TRUE already defined"
#else
#define TRUE (1==1)
#endif

#ifdef FALSE
#error "False already defined"
#else
#define FALSE (!TRUE)
#endif

// existence of typedefs can not be checked within macros
//#define _TYPEDEF_
typedef enum { false = FALSE, true } bool;
//#endif

#ifdef static_assert
#error "static_assert already defined"
#else
#define static_assert _Static_assert // since C11
#endif

// potential necessity: custom printf and exit for the platform
// unfortunately we dont have __COLUMN__ as macro
#define assert(a) if( !( a ) )                            \
{                                                         \
    fprintf( stderr, "%s:%d assertion failure of (%s)\n", \
                             __FILE__, __LINE__, #a );    \
    exit( 1 );                                            \
}                                                         \
static_assert(true, "")

#ifdef IS_SIGNED
#error "IS_SIGNED already defined"
#else
#define IS_SIGNED(Type) (((Type)-1) < 0)
#endif

static_assert(IS_SIGNED(char),   "err: char is unsigned");
static_assert(sizeof(char) == 1, "err: char not 1 byte");
static_assert(sizeof(unsigned char) == 1, "err: char not 1 byte");
static_assert(sizeof(signed char) == 1, "err: char not 1 byte");
static_assert(sizeof(uint8_t) == 1,  "err: uint8_t not 1 byte");
static_assert(sizeof(uint16_t) == 2, "err: uint16_t not 2 byte");
static_assert(sizeof(uint32_t) == 4, "err: uint32_t not 4 byte");
static_assert(sizeof(uint64_t) == 8, "err: uint64_t not 8 byte");
static_assert(sizeof(int8_t) == 1,  "err: int8_t not 1 byte");
static_assert(sizeof(int16_t) == 2, "err: int16_t not 2 byte");
static_assert(sizeof(int32_t) == 4, "err: int32_t not 4 byte");
static_assert(sizeof(int64_t) == 8, "err: int64_t not 8 byte");
//static_assert(sizeof(uint128_t) == 16, "err: uint128_t not 16 byte"); poorly supported
//static_assert(sizeof(int128_t) == 16, "err: int128_t not 16 byte"); poorly supported
#endif // __cplusplus

[jasmcaus]

See this for the static_assert replacement.

Not in favour of the bool enum and the TRUE/FALSE macros -- they're a little clunky.

The IS_SIGNED maybe seems reasonable, but change the IS_SIGNED(Type) (((Type)-1) < 0) to IS_SIGNED(x) (((x)-1) < 0). I can merge that then.