steal openconnect's vasprintf() implementation

2 files changed, 90 insertions, 15 deletions

diff --git a/configure.ac b/configure.ac
index b082047860..ecb69acc73 100644
--- a/configure.ac
+++ b/configure.ac
@@ -152,6 +152,29 @@ AC_C_BIGENDIAN
 dnl No fork on MinGW, disable some self-tests until we fix them.
 dnl Check clock_gettime and pthread_mutex_lock in libc (avoid linking to other libs)
 AC_CHECK_FUNCS([fork inet_ntop inet_pton getrusage getpwuid_r nanosleep daemon getpid clock_gettime iconv localtime vasprintf],,)
+if test "$ac_cv_func_vasprintf" != "yes";then
+  AC_MSG_CHECKING([for va_copy])
+  AC_LINK_IFELSE([AC_LANG_PROGRAM([
+	#include <stdarg.h>
+	va_list a;],[
+	va_list b;
+	va_copy(b,a);
+	va_end(b);])],
+	[AC_DEFINE(HAVE_VA_COPY, 1, [Have va_copy()])
+	AC_MSG_RESULT(va_copy)],
+	[AC_LINK_IFELSE([AC_LANG_PROGRAM([
+		#include <stdarg.h>
+		va_list a;],[
+		va_list b;
+		__va_copy(b,a);
+		va_end(b);])],
+		[AC_DEFINE(HAVE___VA_COPY, 1, [Have __va_copy()])
+		AC_MSG_RESULT(__va_copy)],
+		[AC_MSG_RESULT(no)
+		AC_MSG_ERROR([Your system lacks vasprintf() and va_copy()])])
+	])
+fi
+
 AM_CONDITIONAL(HAVE_FORK, test "$ac_cv_func_fork" != "no")
 
 AC_LIB_HAVE_LINKFLAGS(rt,, [#include <time.h>
diff --git a/lib/vasprintf.c b/lib/vasprintf.c
index f2eeb89b4f..8362942a20 100644
--- a/lib/vasprintf.c
+++ b/lib/vasprintf.c
@@ -1,31 +1,83 @@
+/*
+ * Copyright © 2008-2014 Intel Corporation.
+ *
+ * Authors: David Woodhouse <dwmw2@infradead.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ */
+
 #include <config.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdarg.h>
 #include "vasprintf.h"
 
 #ifndef HAVE_VASPRINTF
 
-#define MAX_BSIZE 1024
-#define NO_MORE_MAX (16*MAX_BSIZE)
-
 int _gnutls_vasprintf(char **strp, const char *fmt, va_list ap)
 {
-	char *buf;
-	int ret, max;
+	va_list ap2;
+	char *res = NULL;
+	int len = 160, len2;
+	int ret = 0;
+	int errno_save = -ENOMEM;
 
-	max = MAX_BSIZE / 2;
+	res = malloc(160);
+	if (!res)
+		goto err;
 
-	do {
-		max *= 2;
-
-		buf = malloc(max);
-		if (buf == NULL)
-			return -1;
+	/* Use a copy of 'ap', preserving it in case we need to retry into
+	   a larger buffer. 160 characters should be sufficient for most
+	   strings in openconnect. */
+#ifdef HAVE_VA_COPY
+	va_copy(ap2, ap);
+#elif defined(HAVE___VA_COPY)
+	__va_copy(ap2, ap);
+#else
+#error No va_copy()!
+	/* You could try this. */
+	ap2 = ap;
+	/* Or this */
+	*ap2 = *ap;
+#endif
+	len = vsnprintf(res, 160, fmt, ap2);
+	va_end(ap2);
 
-		ret = vsnprintf(buf, max, fmt, ap);
+	if (len < 0) {
+	printf_err:
+		errno_save = errno;
+		free(res);
+		res = NULL;
+		goto err;
 	}
-	while (ret > max && max < NO_MORE_MAX);
-	*strp = buf;
+	if (len >= 0 && len < 160)
+		goto out;
+
+	free(res);
+	res = malloc(len+1);
+	if (!res)
+		goto err;
+
+	len2 = vsnprintf(res, len+1, fmt, ap);
+	if (len2 < 0 || len2 > len)
+		goto printf_err;
+
+	ret = 0;
+	goto out;
 
+ err:
+	errno = errno_save;
+	ret = -1;
+ out:
+	*strp = res;
 	return ret;
 }