Get utf8_size from WideCharToMultiByte instead of guessing it

Signed-off-by: Sven Strickroth <email@cs-ware.de>

src/errors.c

@@ -61,11 +61,11 @@ void giterr_set(int error_class, const char *string, ...)
 					(LPWSTR)&lpMsgBuf, 0, NULL);
 
 			if (size) {
-				int utf8_size = size * 4 + 1;
+				int utf8_size = WideCharToMultiByte(CP_UTF8, 0, lpMsgBuf, -1, NULL, 0, NULL, NULL);
 
-				char *lpMsgBuf_utf8 = git__calloc(utf8_size, sizeof(char));
+				char *lpMsgBuf_utf8 = git__malloc(utf8_size * sizeof(char));
 				GITERR_CHECK_ALLOC(lpMsgBuf_utf8);
-				WideCharToMultiByte(CP_UTF8, 0, lpMsgBuf, size, lpMsgBuf_utf8, utf8_size, NULL, NULL);
+				WideCharToMultiByte(CP_UTF8, 0, lpMsgBuf, -1, lpMsgBuf_utf8, utf8_size, NULL, NULL);
 
 				git_buf_PUTS(&buf, ": ");
 				git_buf_puts(&buf, lpMsgBuf_utf8);

src/netops.c

@@ -46,10 +46,10 @@ static void net_set_error(const char *str)
 	int size = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 							  0, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPWSTR)&err_str, 0, 0);
 
-	int utf8_size = size * 4 + 1;
-	char * err_str_utf8 = git__calloc(utf8_size, sizeof(char));
+	int utf8_size = WideCharToMultiByte(CP_UTF8, 0, err_str, -1, NULL, 0, NULL, NULL);
+	char * err_str_utf8 = git__malloc(utf8_size * sizeof(char));
 	GITERR_CHECK_ALLOC(err_str_utf8);
-	WideCharToMultiByte(CP_UTF8, 0, err_str, size, err_str_utf8, utf8_size, NULL, NULL);
+	WideCharToMultiByte(CP_UTF8, 0, err_str, -1, err_str_utf8, utf8_size, NULL, NULL);
 
 	giterr_set(GITERR_NET, "%s: %s", str, err_str_utf8);
 	LocalFree(err_str);