util: add vsprintf version of spdk_sprintf_alloc

-Wformat-nonliteral needs to be disabled since clang triggers it on the
call to vsnprintf() now that it is nested two calls deep.

Change-Id: I228b9d099cfc2b65181941cbb4798b7f8eae3baa
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>

include/spdk/string.h

@@ -42,6 +42,7 @@
 extern "C" {
 #endif
 
+#include <stdarg.h>
 #include <stddef.h>
 
 /**
@@ -53,6 +54,15 @@ extern "C" {
  */
 char *spdk_sprintf_alloc(const char *format, ...) __attribute__((format(printf, 1, 2)));
 
+/**
+ * vsprintf with automatic buffer allocation.
+ *
+ * The return value is the formatted string,
+ * which should be passed to free() when no longer needed,
+ * or NULL on failure.
+ */
+char *spdk_vsprintf_alloc(const char *format, va_list args);
+
 /**
  * Convert string to lowercase in place.
  *

lib/util/string.c

@@ -42,9 +42,9 @@
 #include "spdk/string.h"
 
 char *
-spdk_sprintf_alloc(const char *format, ...)
+spdk_vsprintf_alloc(const char *format, va_list args)
 {
-	va_list args;
+	va_list args_copy;
 	char *buf;
 	size_t bufsize;
 	int rc;
@@ -59,9 +59,9 @@ spdk_sprintf_alloc(const char *format, ...)
 			return NULL;
 		}
 
-		va_start(args, format);
-		rc = vsnprintf(buf, bufsize, format, args);
-		va_end(args);
+		va_copy(args_copy, args);
+		rc = vsnprintf(buf, bufsize, format, args_copy);
+		va_end(args_copy);
 
 		/*
 		 * If vsnprintf() returned a count within our current buffer size, we are done.
@@ -85,6 +85,19 @@ spdk_sprintf_alloc(const char *format, ...)
 	return NULL;
 }
 
+char *
+spdk_sprintf_alloc(const char *format, ...)
+{
+	va_list args;
+	char *ret;
+
+	va_start(args, format);
+	ret = spdk_vsprintf_alloc(format, args);
+	va_end(args);
+
+	return ret;
+}
+
 char *
 spdk_strlwr(char *s)
 {

mk/spdk.common.mk

@@ -54,7 +54,7 @@ ifeq ($(CONFIG_WERROR), y)
 COMMON_CFLAGS += -Werror
 endif
 
-COMMON_CFLAGS += -Wformat -Wformat-security -Wformat-nonliteral
+COMMON_CFLAGS += -Wformat -Wformat-security
 
 COMMON_CFLAGS += -D_GNU_SOURCE