3 files changed, 40 insertions, 6 deletions
diff --git a/common/scummsys.h b/common/scummsys.h
index a425befecf..9d4b6a9677 100644
--- a/common/scummsys.h
+++ b/common/scummsys.h
@@ -302,6 +302,19 @@
 #define MAXPATHLEN 256
 #endif
 
+#ifndef scumm_va_copy
+	#if defined(va_copy)
+		#define scumm_va_copy va_copy
+	#elif defined(__va_copy)
+		#define scumm_va_copy __va_copy
+	#elif defined(_MSC_VER)
+		#define scumm_va_copy(dst, src)       ((dst) = (src))
+	#else
+		#error scumm_va_copy undefined for this port
+	#endif
+#endif
+
+
 
 //
 // Typedef our system types unless they have already been defined by config.h,
diff --git a/common/str.cpp b/common/str.cpp
index 223188bdd6..a2cd4a0193 100644
--- a/common/str.cpp
+++ b/common/str.cpp
@@ -25,8 +25,6 @@
 #include "common/str.h"
 #include "common/util.h"
 
-#include <stdarg.h>
-
 namespace Common {
 
 MemoryPool *g_refCountPool = 0; // FIXME: This is never freed right now
@@ -429,10 +427,22 @@ uint String::hash() const {
 // static
 String String::format(const char *fmt, ...) {
 	String output;
-	assert(output.isStorageIntern());
 
 	va_list va;
 	va_start(va, fmt);
+	output = String::vformat(fmt, va);
+	va_end(va);
+
+	return output;
+}
+
+// static
+String String::vformat(const char *fmt, va_list args) {
+	String output;
+	assert(output.isStorageIntern());
+
+	va_list va;
+	scumm_va_copy(va, args);
 	int len = vsnprintf(output._str, _builtinCapacity, fmt, va);
 	va_end(va);
 
@@ -457,7 +467,7 @@ String String::format(const char *fmt, ...) {
 			assert(!output.isStorageIntern());
 			size = output._extern._capacity;
 
-			va_start(va, fmt);
+			scumm_va_copy(va, args);
 			len = vsnprintf(output._str, size, fmt, va);
 			va_end(va);
 		} while (len == -1 || len >= size - 1);
@@ -468,7 +478,7 @@ String String::format(const char *fmt, ...) {
 	} else {
 		// vsnprintf didn't have enough space, so grow buffer
 		output.ensureCapacity(len, false);
-		va_start(va, fmt);
+		scumm_va_copy(va, args);
 		int len2 = vsnprintf(output._str, len+1, fmt, va);
 		va_end(va);
 		assert(len == len2);
diff --git a/common/str.h b/common/str.h
index 7b97dfe945..8e07b6233d 100644
--- a/common/str.h
+++ b/common/str.h
@@ -24,6 +24,8 @@
 
 #include "common/scummsys.h"
 
+#include <stdarg.h>
+
 namespace Common {
 
 /**
@@ -213,10 +215,19 @@ public:
 	uint hash() const;
 
 	/**
-	 * Printf-like function. Returns a formatted String.
+	 * Print formatted data into a String object. Similar to sprintf,
+	 * except that it stores the result in (variably sized) String
+	 * instead of a fixed size buffer.
 	 */
 	static Common::String format(const char *fmt, ...) GCC_PRINTF(1,2);
 
+	/**
+	 * Print formatted data into a String object. Similar to vsprintf,
+	 * except that it stores the result in (variably sized) String
+	 * instead of a fixed size buffer.
+	 */
+	static Common::String vformat(const char *fmt, va_list args);
+
 public:
 	typedef char *        iterator;
 	typedef const char *  const_iterator;