From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Sat, 24 Oct 2020 16:43:24 +0000 (-0700)
Subject: fix handling of varargs in gvprintf
X-Git-Tag: 2.46.0~20^2^2~4^2~8
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c04c990d93ff5cb43ef184ed11c2c0bad69c523d;p=graphviz

fix handling of varargs in gvprintf

It is not safe to re-va_start a va_list the way this code was previously
operating. This probably worked by coincidence on platforms like x86-64.
---

diff --git a/lib/gvc/gvdevice.c b/lib/gvc/gvdevice.c
index 145f99a7f..ccf8e46f4 100644
--- a/lib/gvc/gvdevice.c
+++ b/lib/gvc/gvdevice.c
@@ -398,8 +398,14 @@ void gvprintf(GVJ_t * job, const char *format, ...)
 
     va_start(argp, format);
 #ifdef HAVE_VSNPRINTF
-    len = vsnprintf((char *)buf, BUFSIZ, format, argp);
+    {
+	va_list argp2;
+	va_copy(argp2, argp);
+	len = vsnprintf((char *)buf, BUFSIZ, format, argp2);
+	va_end(argp2);
+    }
     if (len < 0) {
+	va_end(argp);
 	agerr (AGERR, "gvprintf: %s\n", strerror(errno));
 	return;
     }
@@ -408,8 +414,6 @@ void gvprintf(GVJ_t * job, const char *format, ...)
      * to write the string without truncation. 
      */
 	bp = gmalloc(len + 1);
-	va_end(argp);
-	va_start(argp, format);
 	len = vsprintf(bp, format, argp);
     }
 #else