Mercurial > hg > octave-lojdl > gnulib-hg
diff lib/alloca.c @ 15304:578f64214a48
alloca: port to compilers that can optimize like GCC 4.6.0
* lib/alloca.c (find_stack_direction): New signature, taken from
Autoconf git. This works with GCC 4.6.0. This code should never
be used with GCC 4.6.0 itself, as GCC has alloca, but it might
be used with other compilers that optimize as well as GCC 4.6.0 does.
(alloca): Adjust to new signature.
* m4/alloca.m4 (__AC_LIBOBJ_ALLOCA) [Autoconf version < 2.69]:
New macro, which patches Autoconf in a similar way.
| author | Paul Eggert <eggert@cs.ucla.edu> |
|---|---|
| date | Mon, 20 Jun 2011 15:03:03 -0700 |
| parents | f3a03b79bd9b |
| children | be4eea839ea6 |
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--- a/lib/alloca.c +++ b/lib/alloca.c @@ -93,25 +93,15 @@ static int stack_dir; /* 1 or -1 once known. */ # define STACK_DIR stack_dir -static void -find_stack_direction (char **ptr) +static int +find_stack_direction (int *addr, int depth) { - auto char dummy; /* To get stack address. */ - - if (*ptr == NULL) - { /* Initial entry. */ - *ptr = ADDRESS_FUNCTION (dummy); - - find_stack_direction (ptr); /* Recurse once. */ - } - else - { - /* Second entry. */ - if (ADDRESS_FUNCTION (dummy) > *ptr) - stack_dir = 1; /* Stack grew upward. */ - else - stack_dir = -1; /* Stack grew downward. */ - } + int dir, dummy = 0; + if (! addr) + addr = &dummy; + *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1; + dir = depth ? find_stack_direction (addr, depth - 1) : 0; + return dir + dummy; } # endif /* STACK_DIRECTION == 0 */ @@ -154,10 +144,7 @@ # if STACK_DIRECTION == 0 if (STACK_DIR == 0) /* Unknown growth direction. */ - { - char *addr = NULL; /* Address of first `dummy', once known. */ - find_stack_direction (&addr); - } + STACK_DIR = find_stack_direction (NULL, (size & 1) + 20); # endif /* Reclaim garbage, defined as all alloca'd storage that