Detect system endianness in one line?

Question

Possible Duplicate:
Detecting endianness programmatically in a C++ program
C Macro definition to determine big endian or little endian machine?

Currently, I have the following function to detect the system endianness :

inline bool detectSystemEndianness()
{
    int i = 1;
    char *c = reinterpret_cast<char*>(&i);
    return (c[0] != i);
}

It returns false if little endian, true if big endian. First question : is this function ok ?

Second question : Instead of this function, I would like to initialize a static variable :

static bool _systemEndianness = /* SOMETHING */

How to do that ? (it has to be done at execution-time and not at compile-time ... at least I think so)

But not with the function. If I can avoid this function it's better. — Vincent, Sep 25 '12 at 21:42
@Vincent, why do you want to avoid the call? It will be done during initialization before the rest of your code has a chance to run. — Mark Ransom, Sep 25 '12 at 21:51
@Vincent : The function doesn't have to be documented, it's an implementation detail; only `_systemEndianness` would need documentation. — ildjarn, Sep 25 '12 at 22:11

cppguy · Accepted Answer · 2013-09-10T00:21:38.440

2 ways

1) Have a preprocessor you define for various platforms so you can act on various endianness at compile time instead of runtime (significantly faster but harder to implement without knowing all platforms

2) similar to your function:

inline bool isLittleEndian()
{
    static const int i = 1;
    static const char* const c = reinterpret_cast<const char* const>(&i);
    return (*c == 1);
}
...
static const bool _systemEndianness = isLittleEndian ();

Detect system endianness in one line?

1 Answers1