Fix portability issue in vsnprintf

2 files changed, 94 insertions, 13 deletions

diff --git a/configure.ac b/configure.ac
index c825a0b..96380b9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -202,12 +202,43 @@ dnl functions testing
 dnl ======================================================================
 AX_CREATE_STDINT_H([liblangtag/lt-stdint.h])
 AC_CHECK_HEADERS([dirent.h execinfo.h libgen.h sys/param.h])
-AC_CHECK_FUNCS([backtrace dlopen strndup])
+AC_CHECK_FUNCS([backtrace dlopen strndup vasprintf vsnprintf])
 AC_CHECK_VA_COPY
 
 if test "x$ac_cv_func_dlopen" != xyes; then
 	enable_modules=no
 fi
+if test "x$ac_cv_func_vsnprintf" = xyes; then
+	AC_CACHE_CHECK([Whether vsnprintf is C99-compliant], [lt_cv_c99_vsnprintf],
+		[AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <stdarg.h>
+int
+foo(char *format, ...)
+{
+	va_list ap;
+	char c;
+	int retval = 0;
+
+	va_start(ap, format);
+	if (vsnprintf(&c, 1, format, ap) < 0) {
+		retval = -1;
+	}
+	va_end(ap);
+
+	return retval;
+}
+int
+main(void)
+{
+	char c;
+
+	return foo("foo: %s", "bar");
+}]])],
+		[lt_cv_c99_vsnprintf=yes],[lt_cv_c99_vsnprintf=no],[lt_cv_c99_vsnprintf=no])])
+	if test "x$lt_cv_c99_vsnprintf" = xyes; then
+		AC_DEFINE(LT_HAVE_C99_VSNPRINTF, 1, [Have C99-compliant vsnprintf])
+	fi
+fi
 
 dnl ======================================================================
 dnl gettext stuff
diff --git a/liblangtag/lt-utils.c b/liblangtag/lt-utils.c
index 82b253e..395263a 100644
--- a/liblangtag/lt-utils.c
+++ b/liblangtag/lt-utils.c
@@ -14,6 +14,10 @@
 #include "config.h"
 #endif
 
+#if HAVE_VASPRINTF
+#define _GNU_SOURCE
+#endif
+
 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -126,22 +130,68 @@ char *
 lt_strdup_vprintf(const char *format,
 		  va_list     args)
 {
-	char *retval, c;
-	va_list ap;
-	int size;
+	char *retval;
 
 	lt_return_val_if_fail (format != NULL, NULL);
 
-	va_copy(ap, args);
-
-	size = vsnprintf(&c, 1, format, ap) + 1;
-
-	va_end(ap);
-
-	retval = malloc(sizeof (char) * size);
-	if (retval) {
-		vsprintf(retval, format, args);
+#if HAVE_VASPRINTF
+	if (vasprintf(&retval, format, args) < 0) {
+		retval = NULL;
 	}
+#elif LT_HAVE_C99_VSNPRINTF
+	LT_STMT_START {
+		char c;
+		va_list ap;
+		int size;
+
+		va_copy(ap, args);
+
+		size = vsnprintf(&c, 1, format, ap) + 1;
+
+		va_end(ap);
+
+		retval = malloc(sizeof (char) * size);
+		if (retval) {
+			vsprintf(retval, format, args);
+		}
+	} LT_STMT_END;
+#elif HAVE_VSNPRINTF
+	LT_STMT_START {
+		va_list ap;
+		int size = 1024, n;
+		char *p;
+
+		retval = malloc(size);
+		if (!retval)
+			return NULL;
+
+		while (1) {
+			va_copy(ap, args);
+
+			n = vsnprintf(retval, size, format, ap);
+
+			va_end(ap);
+
+			if (n > -1 && n < size)
+				return retval;
+
+			if (n > -1)
+				size = n + 1;
+			else
+				size *= 2;
+
+			p = realloc(retval, size);
+			if (!p) {
+				free(retval);
+				retval = NULL;
+				break;
+			}
+			retval = p;
+		}
+	} LT_STMT_END;
+#else
+#error no vsnprintf function implemented.
+#endif
 
 	return retval;
 }