Attempt to workaround odd crashes in glslang.

I accidentally managed to reproduce an issue which has been plaguing
users for a while, where glslang throws an assert after closing a game
(and starting a new one).

pthread_setspecific was somehow failing with an EINVAL call, despite the
key never having been freed. I suspect some kind of corruption happening
when dynamic libraries are unloaded, but I doubt this is a bug in either
RetroArch or glslang per-se.

My workaround here is to tear down all TLS use in glslang after we're
done compiling. Somehow this works around the problem for me, and I
don't really see another viable fix. Valgrind does not say anything about the
issue, so doubt it's memory corruption either.

I had to fix a minor TLS leak in glslang as DetachProcess does not free
the PoolIndex TLS.

deps/glslang/glslang.cpp

@@ -21,6 +21,7 @@
 #include <iostream>
 #include <cstring>
 #include <cstdlib>
+#include <mutex>
 
 #include "../../verbosity.h"
 
@@ -31,18 +32,33 @@ struct SlangProcess
 {
    public:
       SlangProcess();
-
       TBuiltInResource& GetResources() { return Resources; }
-      ~SlangProcess() { FinalizeProcess(); }
 
    private:
       TBuiltInResource Resources;
 };
 
+// We don't use glslang from multiple threads, but to be sure.
+// Initializing TLS and freeing it for glslang works around a really bizarre issue
+// where the TLS key is suddenly corrupted *somehow*.
+static std::mutex glslang_global_lock;
+struct SlangProcessHolder
+{
+   SlangProcessHolder()
+   {
+      glslang_global_lock.lock();
+      InitializeProcess();
+   }
+
+   ~SlangProcessHolder()
+   {
+      FinalizeProcess();
+      glslang_global_lock.unlock();
+   }
+};
+
 SlangProcess::SlangProcess()
 {
-   InitializeProcess();
-
    char DefaultConfig[] =
       "MaxLights 32\n"
       "MaxClipPlanes 6\n"
@@ -337,6 +353,7 @@ SlangProcess::SlangProcess()
 bool glslang::compile_spirv(const string &source, Stage stage, std::vector<uint32_t> *spirv)
 {
    static SlangProcess process;
+   SlangProcessHolder process_holder;
 
    TProgram program;
    EShLanguage language;

deps/glslang/glslang/OGLCompilersDLL/InitializeDll.cpp

@@ -158,6 +158,7 @@ bool DetachProcess()
 
     OS_FreeTLSIndex(ThreadInitializeIndex);
     ThreadInitializeIndex = OS_INVALID_TLS_INDEX;
+    DeinitializePoolIndex();
 
     return success;
 }

deps/glslang/glslang/glslang/Include/InitializeGlobals.h

@@ -38,6 +38,7 @@
 namespace glslang {
 
 bool InitializePoolIndex();
+bool DeinitializePoolIndex();
 
 } // end namespace glslang
 

deps/glslang/glslang/glslang/MachineIndependent/PoolAlloc.cpp

@@ -65,6 +65,15 @@ bool InitializePoolIndex()
     return true;
 }
 
+bool DeinitializePoolIndex()
+{
+    if (PoolIndex == OS_INVALID_TLS_INDEX)
+        return false;
+    OS_FreeTLSIndex(PoolIndex);
+    PoolIndex = OS_INVALID_TLS_INDEX;
+    return true;
+}
+
 //
 // Implement the functionality of the TPoolAllocator class, which
 // is documented in PoolAlloc.h.

deps/glslang/glslang/glslang/MachineIndependent/ShaderLang.cpp

@@ -1312,6 +1312,7 @@ int __fastcall ShFinalize()
     glslang::HlslScanContext::deleteKeywordMap();
 #endif
 
+    DetachProcess();
     return 1;
 }