[PATCH 1/2] user32/tests: Fix out-of-bound access in server_end_to_end_callback.

[Yuxuan Shui]

From: Yuxuan Shui

Using test_cmd_w_to_w[str_index - 1] is illegal if str_index is 0.
---
 dlls/user32/tests/dde.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/dlls/user32/tests/dde.c b/dlls/user32/tests/dde.c
index cd97bef165d..00fa72e1fa0 100644
--- a/dlls/user32/tests/dde.c
+++ b/dlls/user32/tests/dde.c
@@ -2430,13 +2430,16 @@ static HDDEDATA CALLBACK server_end_to_end_callback(UINT uType, UINT uFmt, HCONV
         if (winetest_debug > 1) trace("msg %u strA "%s" strW %s\n", msg_index, buffer, wine_dbgstr_w((WCHAR*)buffer));

str_index = msg_index - 4;
-        cmd_w = test_cmd_w_to_w[str_index - 1];
         size_a = strlen(test_cmd_a_to_a) + 1;
-        size_w = (lstrlenW(cmd_w) + 1) * sizeof(WCHAR);
         size_a_to_w = MultiByteToWideChar( CP_ACP, 0, test_cmd_a_to_a, -1, test_cmd_a_to_w,
                                            ARRAY_SIZE(test_cmd_a_to_w)) * sizeof(WCHAR);
-        size_w_to_a = WideCharToMultiByte( CP_ACP, 0, cmd_w, -1,
-                                           test_cmd_w_to_a, sizeof(test_cmd_w_to_a), NULL, NULL );
+        if (str_index)
+        {
+            cmd_w = test_cmd_w_to_w[str_index - 1];
+            size_w = (lstrlenW(cmd_w) + 1) * sizeof(WCHAR);
+            size_w_to_a = WideCharToMultiByte( CP_ACP, 0, cmd_w, -1,
+                                               test_cmd_w_to_a, sizeof(test_cmd_w_to_a), NULL, NULL );
+        }
         switch (str_index)
         {
         case 0:  /* ANSI string */