GCC #define for alignment

[Andrew Haley]

Duane Ellis wrote:
> Hello,
> 
> I have a problem in a memory allocator that acts like Malloc(),  where I
> need to align the result value in the same form as malloc.
> 
> I can easily hard code something :-( but I'd rather use some "well
> known" perhaps ANSI-C  #define for the alignment value.
> It could be a GCC specific #define :-( but I'd rather it not be.
> 
> Simply put, for portability reasons I'd rather not have a hard coded
> thing like this:
> 
>    // ensure proper machine alignment
>    x = (x + 3) & (~3);
> 
> Suggestions? Sure I could use sizeof(void *) also..

You want the largest possible alignment?  That would be something
like

MAX (__alignof__ (double), __alignof__ (void *))

but you'd have to add a few more types to be sure.

Andrew.