[SDL] endian defines
christianbiere at gmx.de
Thu Jan 22 13:59:01 PST 2004
Glenn Maynard wrote:
> Huh? You realize you're nitpicking dummy code, right?
I wasn't especially nit-picking. It's just that I happen to use systems
whith strict alignment rules and I often see software which works
flawlessly on Linux/x86 stumbling over it. And well for the dummy
part - excuse me - but it wasn't me who decided to use certain
C lines instead of just "/* code for little-endian systems */".
> (Programs that really do this usually increment byte_ptr two at a time,
Even worse, he didn't increase the pointer at all! Just kidding...
> so it remains
> even, but since this is only an example, that code doesn't exist.)
Yes, it *remains* even if the base address was even. Often it's not.
buf isn't necessarily aligned on any useful boundary. That's a real
world example and under Solaris the concerned program crashed sometimes
i.e., everytime buf (on the stack) wasn't aligned on a 4 byte boundary
because the code used a blatant (u_int32_t *) cast on it.
There are neat compiler dependend alignment directives but you can do
something like this to enforce a certain alignment:
u_int64_t buf64[4096 / sizeof(u_int64_t)];
char *buf = (char *)&buf64
Of course, if a function requires a certain alignment for its parameters
it should use a correct prototype i.e., not just (char *).
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