win32: fallback for SetThreadErrorMode()

SetThreadErrorMode() is necessary for correct plugin loader semantics,
but it is only available on Windows 7 and later, so it needs to be
loaded at run-time if it is to be used. On Windows 2008 and older,
a fallback is provided to the extent possible.

src/win32/plugin.c

@@ -33,6 +33,39 @@
 #include <windows.h>
 #include <wchar.h>
 
+#if (_WIN32_WINNT < 0x601)
+static BOOL WINAPI SetThreadErrorModeFallback(DWORD mode, DWORD *oldmode)
+{
+    /* TODO: cache the pointer */
+    HANDLE h = GetModuleHandle(_T("kernel32.dll"));
+    if (unlikely(h == NULL))
+        return FALSE;
+
+    BOOL WINAPI (*SetThreadErrorModeReal)(DWORD, DWORD *);
+
+    SetThreadErrorModeReal = GetProcAddress(h, "SetThreadErrorMode");
+    if (SetThreadErrorModeReal != NULL)
+        return SetThreadErrorModeReal(mode, oldmode);
+
+# if (_WIN32_WINNT >= 0x600)
+    DWORD curmode = GetErrorMode();
+# else
+    UINT WINAPI (*GetErrorModeReal)(void);
+    DWORD curmode = 0;
+
+    GetErrorModeReal = (void *)GetProcAddress(h, "GetErrorMode");
+    if (GetErrorModeReal != NULL)
+        curmode = GetErrorModeReal();
+# endif
+    if ((mode & SEM_FAILCRITICALERRORS) != (curmode & SEM_FAILCRITICALERRORS))
+        return FALSE;
+    if (oldmode != NULL)
+        *oldmode = curmode;
+    return TRUE;
+}
+# define SetThreadErrorMode SetThreadErrorModeFallback
+#endif
+
 static char *GetWindowsError( void )
 {
     wchar_t wmsg[256];
@@ -58,14 +91,14 @@ int module_Load( vlc_object_t *p_this, const char *psz_file,
         return -1;
 
     module_handle_t handle = NULL;
-#if (_WIN32_WINNT >= 0x601) && !VLC_WINSTORE_APP
+#if !VLC_WINSTORE_APP
     DWORD mode;
 
     if (SetThreadErrorMode (SEM_FAILCRITICALERRORS, &mode) != 0)
 #endif
     {
         handle = LoadLibraryW (wfile);
-#if (_WIN32_WINNT >= 0x601) && !VLC_WINSTORE_APP
+#if !VLC_WINSTORE_APP
         SetThreadErrorMode (mode, NULL);
 #endif
     }