new module 'aligned-malloc'

[Bruno Haible]

In new gnulib code, I need to allocate memory blocks through malloc() but with
a 16-bytes alignment.

The posix_memalign and memalign functions only help on those platforms where
they exist. It's not possible to emulate posix_memalign or memalign when they
are not present, because when malloc() returned p, we can call free (p)
but not free (p+4) or free (p+8) or similar.

Gnulib has a module 'pagealign_alloc' but it produces a getpagesize() alignment
- not useful (very wasteful) for a 16-bytes alignment.

So here is a module that provides aligned_malloc() and aligned_free().

The alignment is given at compile-time, so that when the desired alignment is
<= the alignment guaranteed by malloc(), there is no overhead. (With an
alignment given at runtime, the aligned_free() function would have to fetch
a back-pointer in all cases, and that means wasting sizeof (void *) bytes
in the case where the desired alignment is small.)


2020-07-21  Bruno Haible  <bruno@clisp.org>

        aligned-malloc: Add tests.
        * tests/test-aligned-malloc.c: New file.
        * modules/aligned-malloc-tests: New file.

        aligned-malloc: New module.
        * lib/aligned-malloc.h: New file.
        * m4/malloc-align.m4: New file.
        * modules/aligned-malloc: New file.
        * doc/posix-functions/posix_memalign.texi: Mention the new module.
        * doc/glibc-functions/memalign.texi: Likewise.

0001-aligned-malloc-New-module.patch
Description: Text Data

0002-aligned-malloc-Add-tests.patch
Description: Text Data