From: Sebastian Harl <sh@tokkee.org>
Date: Wed, 20 Mar 2013 06:30:43 +0000 (-0700)
Subject: utils strbuf: Copy va_lists rather than using them twice.
X-Git-Tag: sysdb-0.1.0~423
X-Git-Url: https://git.tokkee.org/?a=commitdiff_plain;h=6f6e12a94487f7bdf9efe2d5f1733684df6d75a6;p=sysdb.git

utils strbuf: Copy va_lists rather than using them twice.

After a va_list has been passed to a function that uses va_arg(), the value of
the va_list is undefined. Thus, rather copy the list before using it for the
first time to make sure we've got a valid va_list object on the second usage.
---

diff --git a/src/utils/strbuf.c b/src/utils/strbuf.c
index df3ee4b..a48f7bc 100644
--- a/src/utils/strbuf.c
+++ b/src/utils/strbuf.c
@@ -105,6 +105,7 @@ sdb_strbuf_destroy(sdb_strbuf_t *strbuf)
 ssize_t
 sdb_strbuf_vappend(sdb_strbuf_t *strbuf, const char *fmt, va_list ap)
 {
+	va_list aq;
 	int status;
 
 	if ((! strbuf) || (! fmt))
@@ -116,21 +117,27 @@ sdb_strbuf_vappend(sdb_strbuf_t *strbuf, const char *fmt, va_list ap)
 		if (strbuf_resize(strbuf))
 			return -1;
 
+	/* 'ap' is invalid after calling vsnprintf; thus copy before using it */
+	va_copy(aq, ap);
 	status = vsnprintf(strbuf->string + strbuf->pos,
 			strbuf->size - strbuf->pos, fmt, ap);
 
-	if (status < 0)
+	if (status < 0) {
+		va_end(aq);
 		return status;
+	}
 
 	if ((size_t)status >= strbuf->size - strbuf->pos) {
 		strbuf_resize(strbuf);
 
 		/* reset string and try again */
 		strbuf->string[strbuf->pos] = '\0';
-		return sdb_strbuf_vappend(strbuf, fmt, ap);
+		status = (int)sdb_strbuf_vappend(strbuf, fmt, aq);
 	}
+	else
+		strbuf->pos += (size_t)status;
 
-	strbuf->pos += (size_t)status;
+	va_end(aq);
 	return (ssize_t)status;
 } /* sdb_strbuf_vappend */