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/pthread/SDL_syscond.c

@@ -0,0 +1,158 @@
+/*
+  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"
+
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+#include <errno.h>
+#include <pthread.h>
+
+#include "SDL_thread.h"
+#include "SDL_sysmutex_c.h"
+
+struct SDL_cond
+{
+    pthread_cond_t cond;
+};
+
+/* Create a condition variable */
+SDL_cond *
+SDL_CreateCond(void)
+{
+    SDL_cond *cond;
+
+    cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond));
+    if (cond) {
+        if (pthread_cond_init(&cond->cond, NULL) < 0) {
+            SDL_SetError("pthread_cond_init() failed");
+            SDL_free(cond);
+            cond = NULL;
+        }
+    }
+    return (cond);
+}
+
+/* Destroy a condition variable */
+void
+SDL_DestroyCond(SDL_cond * cond)
+{
+    if (cond) {
+        pthread_cond_destroy(&cond->cond);
+        SDL_free(cond);
+    }
+}
+
+/* Restart one of the threads that are waiting on the condition variable */
+int
+SDL_CondSignal(SDL_cond * cond)
+{
+    int retval;
+
+    if (!cond) {
+        return SDL_SetError("Passed a NULL condition variable");
+    }
+
+    retval = 0;
+    if (pthread_cond_signal(&cond->cond) != 0) {
+        return SDL_SetError("pthread_cond_signal() failed");
+    }
+    return retval;
+}
+
+/* Restart all threads that are waiting on the condition variable */
+int
+SDL_CondBroadcast(SDL_cond * cond)
+{
+    int retval;
+
+    if (!cond) {
+        return SDL_SetError("Passed a NULL condition variable");
+    }
+
+    retval = 0;
+    if (pthread_cond_broadcast(&cond->cond) != 0) {
+        return SDL_SetError("pthread_cond_broadcast() failed");
+    }
+    return retval;
+}
+
+int
+SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms)
+{
+    int retval;
+#ifndef HAVE_CLOCK_GETTIME
+    struct timeval delta;
+#endif
+    struct timespec abstime;
+
+    if (!cond) {
+        return SDL_SetError("Passed a NULL condition variable");
+    }
+
+#ifdef HAVE_CLOCK_GETTIME
+    clock_gettime(CLOCK_REALTIME, &abstime);
+
+    abstime.tv_nsec += (ms % 1000) * 1000000;
+    abstime.tv_sec += ms / 1000;
+#else
+    gettimeofday(&delta, NULL);
+
+    abstime.tv_sec = delta.tv_sec + (ms / 1000);
+    abstime.tv_nsec = (delta.tv_usec + (ms % 1000) * 1000) * 1000;
+#endif
+    if (abstime.tv_nsec > 1000000000) {
+        abstime.tv_sec += 1;
+        abstime.tv_nsec -= 1000000000;
+    }
+
+  tryagain:
+    retval = pthread_cond_timedwait(&cond->cond, &mutex->id, &abstime);
+    switch (retval) {
+    case EINTR:
+        goto tryagain;
+        break;
+    case ETIMEDOUT:
+        retval = SDL_MUTEX_TIMEDOUT;
+        break;
+    case 0:
+        break;
+    default:
+        retval = SDL_SetError("pthread_cond_timedwait() failed");
+    }
+    return retval;
+}
+
+/* Wait on the condition variable, unlocking the provided mutex.
+   The mutex must be locked before entering this function!
+ */
+int
+SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex)
+{
+    if (!cond) {
+        return SDL_SetError("Passed a NULL condition variable");
+    } else if (pthread_cond_wait(&cond->cond, &mutex->id) != 0) {
+        return SDL_SetError("pthread_cond_wait() failed");
+    }
+    return 0;
+}
+
+/* vi: set ts=4 sw=4 expandtab: */