Re: Issues in manpage memalign

[Alejandro Colomar <alx.manpages@gmail.com>]

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Hi Paul,

On 3/7/23 23:24, Floyd, Paul wrote:
> Hi
> 
> Quick bit of background. I'm a Valgrind maintainer and recently I've 
> been working on getting Valgrind to work more like the underlying OS / 
> libc implementations of memalign, posix_memalign and aligned_alloc.
> 
> There are several issues with the manpage for memalign and aligned alloc.
> 
> quote:
> 
>         The  obsolete  function  memalign()  allocates size bytes and 
> returns a
>         pointer to the allocated memory.  The memory address will be a 
> multiple
>         of alignment, which must be a power of two.
> 
> endquote:
> 
> The power if two requirement is false for glibc which silently bumps up 
> the alignment to the next power of two.
> 
> quote:
> 
>         The  function aligned_alloc() is the same as memalign(), except 
> for the
>         added restriction that size should be a multiple of alignment.
> 
> endquote:
> 
> This is also false for glibc. In the glibc implementation weak aliases 
> are used so memalign and aligned_alloc call the same function.
> 
> quote:
> 
> ERRORS
>         EINVAL The alignment argument was not a power of two, or was not 
> a mul-
>                tiple of sizeof(void *).
> 
> endquote:
> 
> Both of the above only apply to posix_memalign and not to either 
> memalign or aligned_alloc.
> 
> There is a missing EINVAL description. If the alignment is so large that 
> the allocation will not be possible to satisfy then the call will fail 
> and set errno to EINVAL.

I've CCd glibc, in case someone there can confirm in which direction they
would like the manual page to go.

For now, I'll add a [[deprecated]] attribute in the Synopsis for the
obsolete functions.

Cheers,

Alex

> 
> 
> Regards
> 
> Paul
> 
> 

-- 
<http://www.alejandro-colomar.es/>
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