Don't use DllMain to call altss destructors

Alc/ALc.c

@@ -786,34 +786,22 @@ static void alc_init(void);
 static void alc_deinit(void);
 static void alc_deinit_safe(void);
 
-UIntMap TlsDestructor;
+extern UIntMap TlsDestructors;
 
 #ifndef AL_LIBTYPE_STATIC
-BOOL APIENTRY DllMain(HINSTANCE hModule,DWORD ul_reason_for_call,LPVOID lpReserved)
+BOOL APIENTRY DllMain(HINSTANCE hModule, DWORD reason, LPVOID lpReserved)
 {
-    ALsizei i;
-
-    // Perform actions based on the reason for calling.
-    switch(ul_reason_for_call)
+    switch(reason)
     {
         case DLL_PROCESS_ATTACH:
             /* Pin the DLL so we won't get unloaded until the process terminates */
             GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_PIN | GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
                                (WCHAR*)hModule, &hModule);
-            InitUIntMap(&TlsDestructor, ~0);
+            InitUIntMap(&TlsDestructors, ~0);
             alc_init();
             break;
 
         case DLL_THREAD_DETACH:
-            LockUIntMapRead(&TlsDestructor);
-            for(i = 0;i < TlsDestructor.size;i++)
-            {
-                void *ptr = altss_get(TlsDestructor.array[i].key);
-                altss_dtor_t callback = (altss_dtor_t)TlsDestructor.array[i].value;
-                if(ptr && callback)
-                    callback(ptr);
-            }
-            UnlockUIntMapRead(&TlsDestructor);
             break;
 
         case DLL_PROCESS_DETACH:
@@ -821,7 +809,7 @@ BOOL APIENTRY DllMain(HINSTANCE hModule,DWORD ul_reason_for_call,LPVOID lpReserv
                 alc_deinit();
             else
                 alc_deinit_safe();
-            ResetUIntMap(&TlsDestructor);
+            ResetUIntMap(&TlsDestructors);
             break;
     }
     return TRUE;

Alc/threads.c

@@ -198,6 +198,42 @@ int almtx_timedlock(almtx_t *mtx, const struct timespec *ts)
 }
 
 
+/* An associative map of uint:void* pairs. The key is the TLS index (given by
+ * TlsAlloc), and the value is the altss_dtor_t callback. When a thread exits,
+ * it iterates over the thread-local value for each TLS key and calls the
+ * destructor function if they're both not NULL. Placing a PIMAGE_TLS_CALLBACK
+ * function pointer in a ".CRT$XLx" section (where x is a character A to Z)
+ * ensures the CRT will call it similar to DllMain.
+ */
+UIntMap TlsDestructors;
+
+static void NTAPI altss_callback(void* UNUSED(handle), DWORD reason, void* UNUSED(reserved))
+{
+    ALsizei i;
+
+    if(reason != DLL_THREAD_DETACH)
+        return;
+
+    LockUIntMapRead(&TlsDestructors);
+    for(i = 0;i < TlsDestructors.size;i++)
+    {
+        void *ptr = altss_get(TlsDestructors.array[i].key);
+        altss_dtor_t callback = (altss_dtor_t)TlsDestructors.array[i].value;
+        if(ptr && callback)
+            callback(ptr);
+    }
+    UnlockUIntMapRead(&TlsDestructors);
+}
+#ifdef _MSC_VER
+#pragma section(".CRT$XLB",read)
+__declspec(allocate(".CRT$XLB")) PIMAGE_TLS_CALLBACK altss_callback_ = altss_callback;
+#elif defined(__GNUC__)
+PIMAGE_TLS_CALLBACK altss_callback_ __attribute__((section(".CRT$XLB"))) = altss_callback;
+#else
+#warning "No TLS callback support, thread-local contexts may leak references on poorly written applications."
+PIMAGE_TLS_CALLBACK altss_callback_ = altss_callback;
+#endif
+
 int altss_create(altss_t *tss_id, altss_dtor_t callback)
 {
     DWORD key = TlsAlloc();
@@ -206,13 +242,13 @@ int altss_create(altss_t *tss_id, altss_dtor_t callback)
 
     *tss_id = key;
     if(callback != NULL)
-        InsertUIntMapEntry(&TlsDestructor, key, callback);
+        InsertUIntMapEntry(&TlsDestructors, key, callback);
     return althrd_success;
 }
 
 void altss_delete(altss_t tss_id)
 {
-    InsertUIntMapEntry(&TlsDestructor, tss_id, NULL);
+    RemoveUIntMapKey(&TlsDestructors, tss_id);
     TlsFree(tss_id);
 }
 

Alc/uintmap.h

@@ -14,7 +14,6 @@ typedef struct UIntMap {
     ALsizei limit;
     RWLock lock;
 } UIntMap;
-extern UIntMap TlsDestructor;
 
 void InitUIntMap(UIntMap *map, ALsizei limit);
 void ResetUIntMap(UIntMap *map);