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posix_memalign() bug in glibc-2.2.5?

From: Alceste Scalas
Subject: posix_memalign() bug in glibc-2.2.5?
Date: Sun, 9 Jun 2002 12:31:59 +0200
User-agent: Mutt/1.4i


I  think that  there is  something  strange in  the glibc-2.2.5  (at
least)  implementation of  posix_memalign().  The  glibc  info pages

    | - Function: int posix_memalign (void **MEMPTR, size_t ALIGNMENT,
    |      size_t SIZE)
    | The `posix_memalign' function is similar to the `memalign'
    | function in that it returns a buffer of SIZE bytes aligned to
    | a multiple of ALIGNMENT.  But it adds one requirement to the
    | parameter ALIGNMENT: the value must be a power of two multiple
    | of `sizeof (void *)'.

It is in accordance with the POSIX standard requirements. 

However, the function implementation is quite different:

    | int
    | __posix_memalign (void **memptr, size_t alignment, size_t size)
    | {
    |   void *mem;
    |   /* Test whether the SIZE argument is valid.  It must be a power of
    |      two multiple of sizeof (void *).  */
    |   if (size % sizeof (void *) != 0 || (size & (size - 1)) != 0)
    |     return EINVAL;
    |   mem = __libc_memalign (alignment, size);
    |   if (mem != NULL)
    |     {
    |       *memptr = mem;
    |       return 0;
    |     }
    |   return ENOMEM;
    | }
    | weak_alias (__posix_memalign, posix_memalign)

The dimension check  is performed on the "size"  parameter, while it
should be done on "alignment". 

It  both  violates the  POSIX  standard,  and  creates a  number  of
problems (allocated memory must be a multiple of sizeof(void*) and a
power of 2, with obvious memory wasting issues).

Am I wrong?  ?:-\

Regards, and keep up the good work,

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