Fix sprintf memory leak by using realloc to shrink buffer to the proper size.

2 files changed, 12 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index c5366227..8e9ef895 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2016-05-03         Andrew J. Schorr     <aschorr@telemetry-investments.com>
+
+	* builtin.c (format_tree): After the string has been rendered, use
+	realloc to shrink the buffer to the needed size. Otherwise, the minimum
+	buffer size of 512 bytes can result in lots of wasted memory if many
+	sprintf results are stored in an array.
+
 2016-05-02         Andrew J. Schorr     <aschorr@telemetry-investments.com>
 
 	* gawkapi.h (gawk_api_major_version, gawk_api_minor_version): Add
diff --git a/builtin.c b/builtin.c
index 108bcb89..d7101c26 100644
--- a/builtin.c
+++ b/builtin.c
@@ -660,7 +660,7 @@ format_tree(
 	int i, nc;
 	bool toofew = false;
 	char *obuf, *obufout;
-	size_t osiz, ofre;
+	size_t osiz, ofre, olen_final;
 	const char *chbuf;
 	const char *s0, *s1;
 	int cs1;
@@ -1572,7 +1572,10 @@ mpf1:
 			_("too many arguments supplied for format string"));
 	}
 	bchunk(s0, s1 - s0);
-	r = make_str_node(obuf, obufout - obuf, ALREADY_MALLOCED);
+	olen_final = obufout - obuf;
+	if (ofre > 0)
+		erealloc(obuf, char *, olen_final + 2, "format_tree");
+	r = make_str_node(obuf, olen_final, ALREADY_MALLOCED);
 	obuf = NULL;
 out:
 	{