Fix compatibility with latest L4D2 update

2 files changed, 58 insertions, 11 deletions

diff --git a/src/kvsys.c b/src/kvsys.c
index 25344da..1d09b0f 100644
--- a/src/kvsys.c
+++ b/src/kvsys.c
@@ -1,5 +1,6 @@
 /*
  * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com>
+ * Copyright © 2024 Willian Henrique <wsimanbrazil@yahoo.com.br>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -25,29 +26,35 @@
 #include "mem.h"
 #include "os.h"
 #include "vcall.h"
+#include "x86.h"
 
 FEATURE()
 
 IMPORT void *KeyValuesSystem(void); // vstlib symbol
 static void *kvs;
-DECL_VFUNC(int, GetSymbolForString, 3, const char *, bool)
-DECL_VFUNC(const char *, GetStringForSymbol, 4, int)
+static int vtidx_GetSymbolForString = 3, vtidx_GetStringForSymbol = 4;
+static bool iskvv2 = false;
+DECL_VFUNC_DYN(int, GetSymbolForString, const char *, bool)
+DECL_VFUNC_DYN(const char *, GetStringForSymbol, int)
 
 const char *kvsys_symtostr(int sym) { return GetStringForSymbol(kvs, sym); }
 int kvsys_strtosym(const char *s) { return GetSymbolForString(kvs, s, true); }
 
 struct KeyValues *kvsys_getsubkey(struct KeyValues *kv, int sym) {
-	for (kv = kv->child; kv; kv = kv->next) if (kv->keyname == sym) return kv;
+	for (kv = iskvv2 ? kv->v2.child : kv->v1.child; kv;
+			kv = iskvv2 ? kv->v2.next : kv->v1.next) {
+		if (kv->keyname == sym) return kv;
+	}
 	return 0;
 }
 
 // this is trivial for now, but may need expansion later; see header comment
-const char *kvsys_getstrval(struct KeyValues *kv) { return kv->strval; }
+const char *kvsys_getstrval(const struct KeyValues *kv) { return kv->strval; }
 
 void kvsys_free(struct KeyValues *kv) {
 	while (kv) {
-		kvsys_free(kv->child);
-		struct KeyValues *next = kv->next;
+		kvsys_free(iskvv2 ? kv->v2.child : kv->v1.child);
+		struct KeyValues *next = iskvv2 ? kv->v2.next : kv->v1.next;
 		// NOTE! could (should?) call the free function in IKeyValuesSystem but
 		// we instead assume pooling is compiled out in favour of the IMemAlloc
 		// stuff, and thus call the latter directly for less overhead
@@ -68,12 +75,38 @@ static const char *VCALLCONV hook_GetStringForSymbol(void *this, int s) {
 	return ret;
 }
 
+// XXX: 5th instance of this in the codebase, should REALLY tidy up soon
+#ifdef _WIN32
+#define NVDTOR 1
+#else
+#define NVDTOR 2
+#endif
+
+static void detectabichange(void **kvsvt) {
+	// When no virtual destructor is present, the 6th function in the KVS vtable
+	// is AddKeyValuesToMemoryLeakList, which is a nop in release builds.
+	// L4D2 2.2.3.8 (14th May 2024) adds a virtual destructor which pushes
+	// everything down, so the 6th function is not a nop any more. This
+	// coincides with changes to the KeyValues struct layout (see above).
+	uchar *insns = kvsvt[5];
+	// should be RETI16 on Windows (thiscall, callee cleanup) and RET on Linux
+	// (cdecl, caller cleanup) but let's just check both to be thorough
+	if (insns[0] != X86_RETI16 && insns[0] != X86_RET) {
+		iskvv2 = true;
+		vtidx_GetSymbolForString += NVDTOR;
+		vtidx_GetStringForSymbol += NVDTOR;
+	}
+}
+
 INIT {
 	kvs = KeyValuesSystem();
-	// NOTE: this is technically redundant for early versions but I CBA writing
-	// a version check; it's easier to just do this unilaterally.
+	// NOTE: this hook is technically redundant for early versions but I CBA
+	// writing a version check; it's easier to just do this unilaterally. The
+	// kvs ABI check is probably relevant for other games, but none that we
+	// currently actively support
 	if (GAMETYPE_MATCHES(L4D2x)) {
 		void **kvsvt = mem_loadptr(kvs);
+		detectabichange(kvsvt);
 		if (!os_mprot(kvsvt + vtidx_GetStringForSymbol, sizeof(void *),
 				PAGE_READWRITE)) {
 			errmsg_warnx("couldn't make KeyValuesSystem vtable writable");
@@ -90,7 +123,8 @@ INIT {
 
 END {
 	if (orig_GetStringForSymbol) {
-		unhook_vtable(*(void ***)kvs, 4, (void *)orig_GetStringForSymbol);
+		unhook_vtable(*(void ***)kvs, vtidx_GetStringForSymbol,
+				(void *)orig_GetStringForSymbol);
 	}
 }
 
diff --git a/src/kvsys.h b/src/kvsys.h
index 0c8217d..de97b01 100644
--- a/src/kvsys.h
+++ b/src/kvsys.h
@@ -1,5 +1,6 @@
 /*
  * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com>
+ * Copyright © 2024 Willian Henrique <wsimanbrazil@yahoo.com.br>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -32,7 +33,19 @@ struct KeyValues {
 	bool hasescapes;
 	bool evalcond;
 	//char unused;
-	struct KeyValues *next, *child, *chain;
+	union {
+		struct {
+			struct KeyValues *next, *child, *chain;
+		} v1;
+		struct {
+			void *kvsys;
+			bool haskvsys; // wasting 3 bytes for no reason, brilliant
+			struct KeyValues *next, *child, *chain;
+		} v2;
+	};
+	// this was supposedly added here at some point but we don't use it:
+	// typedef bool (*GetSymbolProc_t)(const char *pKey);
+	// GetSymbolProc_t m_pExpressionGetSymbolProc;
 };
 
 /* Wraps the engine IKeyValuesSystem::GetStringForSymbol() call. */
@@ -49,7 +62,7 @@ struct KeyValues *kvsys_getsubkey(struct KeyValues *kv, int sym);
  * IMPORTANT: currently does not automatically coerce types like the engine
  * does. This can be added later if actually required.
  */
-const char *kvsys_getstrval(struct KeyValues *kv);
+const char *kvsys_getstrval(const struct KeyValues *kv);
 
 /* Free a KV object and all its subkeys. */
 void kvsys_free(struct KeyValues *kv);