alignment (was Re: lynx-dev lynx2.8.5dev.13)

[Leonid Pauzner]

22-Jan-2003 19:06 Thomas Dickey wrote:
>> > 2003-01-22 (2.8.5dev.13)
>> > * change new memory-allocation in HTString.c and GridText.c to provide 
>> > pointers
>> >   to data aligned to the host's pointer-size, to work on Tru64 where this
>> >   happens to be 8 -TD

> I didn't think of that at first either, but the runtime messages are very
> noticable.

sizeof(double) will be more portable, from alloca.c:


/* alloca.c -- allocate automatically reclaimed memory
   (Mostly) portable public-domain implementation -- D A Gwyn

   This implementation of the PWB library alloca function,
   which is used to allocate space off the run-time stack so
   that it is automatically reclaimed upon procedure exit,
   was inspired by discussions with J. Q. Johnson of Cornell.
   J.Otto Tennant <address@hidden> contributed the Cray support.
[...]

   It is very important that sizeof(header) agree with malloc
   alignment chunk size.  The following default should work okay.  */

#ifndef ALIGN_SIZE
#define ALIGN_SIZE      sizeof(double)
#endif



--- 2_8_5dev.12n        2003-01-21 12:52:34.000000000 +0000
+++ 2_8_5dev.13 2003-01-22 23:42:00.000000000 +0000
@@ -116,7 +117,10 @@
  Changes since Lynx 2.8 release
  
===============================================================================

-+2003-01-20 (2.8.5dev.13)
++2003-01-22 (2.8.5dev.13)
++* change new memory-allocation in HTString.c and GridText.c to provide 
pointers
++  to data aligned to the host's pointer-size, to work on Tru64 where this
++  happens to be 8 -TD

++/*
++ * The HTPool.data[] array has to align the same as malloc() would, to make 
the
++ * ALLOC_POOL scheme portable.  For many platforms, that is the same as the
++ * number of bytes in a pointer.  It may be larger, e.g., on machines which
++ * have more stringent requirements for floating point.  32-bits are plenty 
for
++ * representing styles, but we may need 64-bit or 128-bit alignment.
++ *
++ * The real issue is that performance is degraded if the alignment is not met,
++ * and some platforms such as Tru64 generate lots of warning messages.
++ */
++#define ALIGN_SIZE     8


@@ -1665,12 +1670,13 @@

-+#define EXTRA_LEN size_t      /* type we use for length */
++#define EXTRA_TYPE size_t             /* type we use for length */
++#define EXTRA_SIZE sizeof(void *)     /* alignment >= sizeof(EXTRA_TYPE) */
 +
 +PUBLIC void   HTSAFree_extra ARGS1(
 +      char *,         s)
 +{
-+    free((char *)s - sizeof(EXTRA_LEN));
++    free(s - EXTRA_SIZE);
 +}
 +



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