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10.46.5 aligned_alloc ¶

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

POSIX specification:
https://pubs.opengroup.org/onlinepubs/9799919799/functions/aligned_alloc.html

Documentation:
man aligned_alloc

Gnulib module: aligned_alloc

Portability problems fixed by Gnulib:

• This function fails if the alignment argument is smaller than sizeof (void *) on some platforms: macOS 14, AIX 7.3.1.
• This function returns a null pointer if the requested size is not a multiple of the alignment: Solaris 11.4.
• This function returns a null pointer if the size argument is zero: macOS 15, AIX 7.3, Solaris 11.4.
• On some platforms, aligned_alloc crashes if the requested size is not a multiple of the alignment: AddressSanitizer (gcc 11.2 or clang 13).

Portability problems not fixed by Gnulib:

• 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.
• If the alignment and size are absurdly large, this function crashes: glibc 2.40.

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

• The Gnulib module alignalloc provides a portable function alignalloc that is a near-substitute for glibc aligned_alloc, except that the result must be freed with alignfree rather than plain free.
• The Gnulib module aligned-malloc provides functions for allocating and freeing blocks of suitably aligned memory.
• The Gnulib module pagealign_alloc provides a similar API for allocating and freeing blocks of memory aligned on a system page boundary.