decklink: Fix broken COM string conversion

WideCharToMultiByte return is the string length without null terminate
character if passed "cchWideChar" does not include the null terminate
character size. Instead of passing the exact string length, pass -1 so that
the API can understand the input string is null terminated already and
returned value from the API includes the character.

Fixes: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/3023
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5446>

diff --git a/subprojects/gst-plugins-bad/sys/decklink/gstdecklink.h b/subprojects/gst-plugins-bad/sys/decklink/gstdecklink.h
index 7c811e0..5c66351 100644 (file)
--- a/subprojects/gst-plugins-bad/sys/decklink/gstdecklink.h
+++ b/subprojects/gst-plugins-bad/sys/decklink/gstdecklink.h
@@ -37,19 +37,17 @@
 #define COMSTR_T BSTR
 #define CONVERT_COM_STRING(s) G_STMT_START { \
   BSTR _s = (BSTR)s; \
-  int _s_length = ::SysStringLen(_s); \
-  int _length = ::WideCharToMultiByte(CP_ACP, 0, (wchar_t*)_s, _s_length, NULL, 0, NULL, NULL); \
+  int _length = ::WideCharToMultiByte(CP_ACP, 0, (wchar_t*)_s, -1, NULL, 0, NULL, NULL); \
   s = (char *) malloc(_length); \
-  ::WideCharToMultiByte(CP_ACP, 0, (wchar_t*)_s, _s_length, s, _length, NULL, NULL); \
+  ::WideCharToMultiByte(CP_ACP, 0, (wchar_t*)_s, -1, s, _length, NULL, NULL); \
   ::SysFreeString(_s); \
 } G_STMT_END
 #define FREE_COM_STRING(s) free(s);
 #define CONVERT_TO_COM_STRING(s) G_STMT_START { \
   char * _s = (char *)s; \
-  int _s_length = strlen((char*)_s); \
-  int _length = ::MultiByteToWideChar(CP_ACP, 0, (char*)_s, _s_length, NULL, 0); \
+  int _length = ::MultiByteToWideChar(CP_ACP, 0, (char*)_s, -1, NULL, 0); \
   s = ::SysAllocStringLen(NULL, _length); \
-  ::MultiByteToWideChar(CP_ACP, 0, (char*)_s, _s_length, s, _length); \
+  ::MultiByteToWideChar(CP_ACP, 0, (char*)_s, -1, s, _length); \
   g_free(_s); \
 } G_STMT_END
 #elif defined(__APPLE__)