Handle ordinals in GetProcAddress detour (#66)

As it turns out, symbols exported by a DLL don't necessary have to have text symbols - but they do have a number, the symbol ordinal, which is a valid way to address and access the symbol. GetProcAddress supports this behaviour - in this case, the ordinal is passed as the pointer value. Which, in Doorstop's detour, still gets treated as a string, and which subsequently causes lstrcmp to segfault under some very specific conditions (i.e. when the calling module tries to resolve a procedure by its ordinal).

In my case Unity 6 was accessing the 0x65 ordinal of d3d12.dll (located in system directory). (Did some poking - the symbol is named, which is weird, and named "D3D12CreateDevice", which checks out.)

As per GetProcAddress docs, if the value of the lpProcName pointer is an ordinal, high-word value of the pointer must be zero. This pull request addresses that quirk by inserting HIWORD macro as an additional condition to the detour check routine.

GetProcAddress docs: https://learn.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-getprocaddress

Author: Kriper1111

src/windows/entrypoint.c

@@ -137,8 +137,10 @@ void capture_mono_path(void *handle) {
 
 bool_t initialized = FALSE;
 void *WINAPI get_proc_address_detour(void *module, char *name) {
+    // If the lpProcName pointer contains an ordinal rather than a string,
+    // high-word value of the pointer is zero (see PR #66)
 #define REDIRECT_INIT(init_name, init_func, target, extra_init)                \
-    if (lstrcmpA(name, init_name) == 0) {                                      \
+    if (HIWORD(name) && lstrcmpA(name, init_name) == 0) {                      \
         if (!initialized) {                                                    \
             initialized = TRUE;                                                \
             LOG("Got %S at %p", init_name, module);                            \