Fixed crash if initialization of EGL failed but was tried again later.

The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().

src/thread/stdcpp/SDL_systhread.cpp

@@ -0,0 +1,167 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2015 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "../../SDL_internal.h"
+
+/* Thread management routines for SDL */
+
+extern "C" {
+#include "SDL_thread.h"
+#include "../SDL_thread_c.h"
+#include "../SDL_systhread.h"
+#include "SDL_log.h"
+}
+
+#include <mutex>
+#include <thread>
+#include <system_error>
+
+#ifdef __WINRT__
+#include <Windows.h>
+#endif
+
+static void
+RunThread(void *args)
+{
+    SDL_RunThread(args);
+}
+
+extern "C"
+int
+SDL_SYS_CreateThread(SDL_Thread * thread, void *args)
+{
+    try {
+        std::thread cpp_thread(RunThread, args);
+        thread->handle = (void *) new std::thread(std::move(cpp_thread));
+        return 0;
+    } catch (std::system_error & ex) {
+        SDL_SetError("unable to start a C++ thread: code=%d; %s", ex.code(), ex.what());
+        return -1;
+    } catch (std::bad_alloc &) {
+        SDL_OutOfMemory();
+        return -1;
+    }
+}
+
+extern "C"
+void
+SDL_SYS_SetupThread(const char *name)
+{
+    // Make sure a thread ID gets assigned ASAP, for debugging purposes:
+    SDL_ThreadID();
+    return;
+}
+
+extern "C"
+SDL_threadID
+SDL_ThreadID(void)
+{
+#ifdef __WINRT__
+    return GetCurrentThreadId();
+#else
+    // HACK: Mimick a thread ID, if one isn't otherwise available.
+    static thread_local SDL_threadID current_thread_id = 0;
+    static SDL_threadID next_thread_id = 1;
+    static std::mutex next_thread_id_mutex;
+
+    if (current_thread_id == 0) {
+        std::lock_guard<std::mutex> lock(next_thread_id_mutex);
+        current_thread_id = next_thread_id;
+        ++next_thread_id;
+    }
+
+    return current_thread_id;
+#endif
+}
+
+extern "C"
+int
+SDL_SYS_SetThreadPriority(SDL_ThreadPriority priority)
+{
+    // Thread priorities do not look to be settable via C++11's thread
+    // interface, at least as of this writing (Nov 2012).  std::thread does
+    // provide access to the OS' native handle, however, and some form of
+    // priority-setting could, in theory, be done through this interface.
+    //
+    // WinRT: UPDATE (Aug 20, 2013): thread priorities cannot be changed
+    // on WinRT, at least not for any thread that's already been created.
+    // WinRT threads appear to be based off of the WinRT class,
+    // ThreadPool, more info on which can be found at:
+    // http://msdn.microsoft.com/en-us/library/windows/apps/windows.system.threading.threadpool.aspx
+    //
+    // For compatibility sake, 0 will be returned here.
+    return (0);
+}
+
+extern "C"
+void
+SDL_SYS_WaitThread(SDL_Thread * thread)
+{
+    if ( ! thread) {
+        return;
+    }
+
+    try {
+        std::thread * cpp_thread = (std::thread *) thread->handle;
+        if (cpp_thread->joinable()) {
+            cpp_thread->join();
+        }
+    } catch (std::system_error &) {
+        // An error occurred when joining the thread.  SDL_WaitThread does not,
+        // however, seem to provide a means to report errors to its callers
+        // though!
+    }
+}
+
+extern "C"
+void
+SDL_SYS_DetachThread(SDL_Thread * thread)
+{
+    if ( ! thread) {
+        return;
+    }
+
+    try {
+        std::thread * cpp_thread = (std::thread *) thread->handle;
+        if (cpp_thread->joinable()) {
+            cpp_thread->detach();
+        }
+    } catch (std::system_error &) {
+        // An error occurred when detaching the thread.  SDL_DetachThread does not,
+        // however, seem to provide a means to report errors to its callers
+        // though!
+    }
+}
+
+extern "C"
+SDL_TLSData *
+SDL_SYS_GetTLSData()
+{
+    return SDL_Generic_GetTLSData();
+}
+
+extern "C"
+int
+SDL_SYS_SetTLSData(SDL_TLSData *data)
+{
+    return SDL_Generic_SetTLSData(data);
+}
+
+/* vi: set ts=4 sw=4 expandtab: */