@node aligned_alloc
@subsection @code{aligned_alloc}
@findex aligned_alloc

ISO C23 specification:@* @url{https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf} section 7.24.3.1.

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/aligned_alloc.html}

Documentation:@* @uref{https://www.kernel.org/doc/man-pages/online/pages/man3/aligned_alloc.3.html,,man aligned_alloc}

Gnulib module: aligned_alloc
@mindex aligned_alloc

Portability problems fixed by Gnulib:
@itemize
@item
This function fails if the alignment argument is smaller than
@code{sizeof (void *)} on some platforms:
macOS 14, AIX 7.3.1.

@item
This function returns a null pointer if the requested size is
not a multiple of the alignment:
Solaris 11.4.

@item
This function returns a null pointer if the size argument is zero:
macOS 15, AIX 7.3, Solaris 11.4.

@item
On some platforms, @code{aligned_alloc} crashes if the requested size is
not a multiple of the alignment:
AddressSanitizer (gcc 11.2 or clang 13).
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
This function is missing on many older platforms:
glibc 2.15, macOS 10.14, FreeBSD 6.4, NetBSD 7.1, OpenBSD 6.0, Minix 3.1.8, AIX 7.1, HP-UX 11.31, Solaris 11.3, Cygwin 1.7.x, mingw, MSVC 14, Android 8.1.

@item
If the alignment and size are absurdly large, this function crashes:
@c https://sourceware.org/PR32301
glibc 2.42.
@end itemize

Gnulib has partial substitutes for @code{aligned_alloc}
that do not crash even if the AddressSanitizer bug is present:

@itemize
@item
@mindex alignalloc
The Gnulib module @code{alignalloc} provides a portable function
@code{alignalloc} that is a near-substitute for glibc
@code{aligned_alloc}, except that the result must be freed
with @code{alignfree} rather than plain @code{free}.

@item
@mindex aligned-malloc
The Gnulib module @code{aligned-malloc} provides functions for
allocating and freeing blocks of suitably aligned memory.

@item
@mindex pagealign_alloc
The Gnulib module @code{pagealign_alloc} provides a similar API for
allocating and freeing blocks of memory aligned on a system page boundary.
@end itemize