Minor improvement in gsub() memory management.

2 files changed, 16 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index ebb1f1f2..05aaacd0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2014-08-13         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* builtin.c (do_sub): Move initial allocation of the replacement
+	string down towards code to do the replacement, with a (we hope)
+	better guesstimate of how much to initially allocate. The idea
+	is to avoid unnecessary realloc() calls by making a better guess
+	at how much to allocate.  This came up in an email discussion
+	with Tom Dickey about mawk's gsub().
+
 2014-08-12         Arnold D. Robbins     <arnold@skeeve.com>
 
 	OFS being set should rebuild $0 using previous OFS if $0
diff --git a/builtin.c b/builtin.c
index 077575fa..0995fdf7 100644
--- a/builtin.c
+++ b/builtin.c
@@ -2786,16 +2786,11 @@ set_how_many:
 
 	text = t->stptr;
 	textlen = t->stlen;
-	buflen = textlen + 2;
 
 	repl = s->stptr;
 	replend = repl + s->stlen;
 	repllen = replend - repl;
 
-	emalloc(buf, char *, buflen + 2, "do_sub");
-	buf[buflen] = '\0';
-	buf[buflen + 1] = '\0';
-
 	ampersands = 0;
 
 	/*
@@ -2854,6 +2849,13 @@ set_how_many:
 	}
 
 	lastmatchnonzero = false;
+
+	/* guesstimate how much room to allocate; +2 forces > 0 */
+	buflen = textlen + (ampersands + 1) * repllen + 2;
+	emalloc(buf, char *, buflen + 2, "do_sub");
+	buf[buflen] = '\0';
+	buf[buflen + 1] = '\0';
+
 	bp = buf;
 	for (current = 1;; current++) {
 		matches++;