posix_memalign() and FreeBSD

[Giorgos Keramidas]

Hi Stefan and all,

I suspected that the fact that posix_memalign() use has to be
manually disabled (or removed through autoconf) for FreeBSD, was
caused by allocating memory with posix_memalign() but later
freeing it with Emacs' own malloc()/free() implementation.

This results in random crashes during "make bootstrap" for the
HEAD of the CVS tree -- which usually happens pretty fast,
i.e. when building the autoload list of some module.

Disabling posix_memalign() when SYSTEM_MALLOC is not used, with
the following patch fixes bootstrapping on FreeBSD/amd64 here.

Since the internal GNU malloc() of Emacs doesn't support
posix_memalign(), do you think this is a reasonable change, or
should I revert it in my local tree and see if I can track down
where memory is allocated with posix_memalign() and released with
GNU malloc's free()?

%%% begin emacs-posix-memalign.patch
Index: alloc.c
===================================================================
*** alloc.c     (revision 88)
--- alloc.c     (working copy)
***************
*** 948,954 ****
  #define ABLOCKS_BUSY(abase) ((abase)->blocks[0].abase)
  
  /* Pointer to the (not necessarily aligned) malloc block.  */
! #ifdef HAVE_POSIX_MEMALIGN
  #define ABLOCKS_BASE(abase) (abase)
  #else
  #define ABLOCKS_BASE(abase) \
--- 948,954 ----
  #define ABLOCKS_BUSY(abase) ((abase)->blocks[0].abase)
  
  /* Pointer to the (not necessarily aligned) malloc block.  */
! #if SYSTEM_MALLOC && HAVE_POSIX_MEMALIGN
  #define ABLOCKS_BASE(abase) (abase)
  #else
  #define ABLOCKS_BASE(abase) \
***************
*** 989,995 ****
        mallopt (M_MMAP_MAX, 0);
  #endif
  
! #ifdef HAVE_POSIX_MEMALIGN
        {
        int err = posix_memalign (&base, BLOCK_ALIGN, ABLOCKS_BYTES);
        if (err)
--- 989,995 ----
        mallopt (M_MMAP_MAX, 0);
  #endif
  
! #if SYSTEM_MALLOC && HAVE_POSIX_MEMALIGN
        {
        int err = posix_memalign (&base, BLOCK_ALIGN, ABLOCKS_BYTES);
        if (err)
***************
*** 1105,1111 ****
        }
        eassert ((aligned & 1) == aligned);
        eassert (i == (aligned ? ABLOCKS_SIZE : ABLOCKS_SIZE - 1));
! #ifdef HAVE_POSIX_MEMALIGN
        eassert ((unsigned long)ABLOCKS_BASE (abase) % BLOCK_ALIGN == 0);
  #endif
        free (ABLOCKS_BASE (abase));
--- 1105,1111 ----
        }
        eassert ((aligned & 1) == aligned);
        eassert (i == (aligned ? ABLOCKS_SIZE : ABLOCKS_SIZE - 1));
! #if SYSTEM_MALLOC && HAVE_POSIX_MEMALIGN
        eassert ((unsigned long)ABLOCKS_BASE (abase) % BLOCK_ALIGN == 0);
  #endif
        free (ABLOCKS_BASE (abase));
%%% end emacs-posix-memalign.patch

- Giorgos