Re: [patch #6569] Allow grep to work in small stack environment

[Jim Meyering]

Paolo Bonzini wrote:
> Update of patch #6569 (project grep):
>                   Status:                    None => Ready For Test
>
> Reply to this item at:
>
>   <http://savannah.gnu.org/patch/?6569>

Here's an adjusted patch:
  - use xnmalloc, not malloc+test+return, so we don't ignore malloc failure.
  - use sizeof *VAR, not "sizeof TYPE" -- the former is more maintainable.
  - adjust indentation to retain declaration alignment

>From ced405b364654f13cb1926d7622be167436a8e36 Mon Sep 17 00:00:00 2001
From: Patrick Boyd <address@hidden>
Date: Fri, 27 Aug 2010 10:31:37 +0200
Subject: [PATCH] dfa: reduce stack usage

* src/dfa.c (dfaanalyze): Allocate GRPS and LABELS arrays from heap,
not on the stack.
---
 src/dfa.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/dfa.c b/src/dfa.c
index 5da59d8..0563d8f 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -2290,8 +2290,8 @@ dfaanalyze (struct dfa *d, int searchflag)
 void
 dfastate (int s, struct dfa *d, int trans[])
 {
-  position_set grps[NOTCHAR];  /* As many as will ever be needed. */
-  charclass labels[NOTCHAR];   /* Labels corresponding to the groups. */
+  position_set *grps;          /* As many as will ever be needed. */
+  charclass *labels;           /* Labels corresponding to the groups. */
   int ngrps = 0;               /* Number of groups actually used. */
   position pos;                        /* Current position being considered. */
   charclass matches;           /* Set of matching characters. */
@@ -2315,6 +2315,9 @@ dfastate (int s, struct dfa *d, int trans[])
 #endif
   int i, j, k;

+  grps = xnmalloc (NOTCHAR, sizeof *grps);
+  labels = xnmalloc (NOTCHAR, sizeof *labels);
+
   /* Initialize the set of letters, if necessary. */
   if (! initialized)
     {
@@ -2577,6 +2580,8 @@ dfastate (int s, struct dfa *d, int trans[])
     free(grps[i].elems);
   free(follows.elems);
   free(tmp.elems);
+  free(grps);
+  free(labels);
 }

 /* Some routines for manipulating a compiled dfa's transition tables.
--
1.7.2.2.510.g7180a