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/filesystem/unix/SDL_sysfilesystem.c

@@ -0,0 +1,210 @@
+/*
+  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"
+
+#ifdef SDL_FILESYSTEM_UNIX
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+/* System dependent filesystem routines                                */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <limits.h>
+
+#ifdef __FREEBSD__
+#include <sys/sysctl.h>
+#endif
+
+#include "SDL_error.h"
+#include "SDL_stdinc.h"
+#include "SDL_filesystem.h"
+
+static char *
+readSymLink(const char *path)
+{
+    char *retval = NULL;
+    ssize_t len = 64;
+    ssize_t rc = -1;
+
+    while (1)
+    {
+        char *ptr = (char *) SDL_realloc(retval, (size_t) len);
+        if (ptr == NULL) {
+            SDL_OutOfMemory();
+            break;
+        }
+
+        retval = ptr;
+
+        rc = readlink(path, retval, len);
+        if (rc == -1) {
+            break;  /* not a symlink, i/o error, etc. */
+        } else if (rc < len) {
+            retval[rc] = '\0';  /* readlink doesn't null-terminate. */
+            return retval;  /* we're good to go. */
+        }
+
+        len *= 2;  /* grow buffer, try again. */
+    }
+
+    SDL_free(retval);
+    return NULL;
+}
+
+
+char *
+SDL_GetBasePath(void)
+{
+    char *retval = NULL;
+
+#if defined(__FREEBSD__)
+    char fullpath[PATH_MAX];
+    size_t buflen = sizeof (fullpath);
+    const int mib[] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
+    if (sysctl(mib, SDL_arraysize(mib), fullpath, &buflen, NULL, 0) != -1) {
+        retval = SDL_strdup(fullpath);
+        if (!retval) {
+            SDL_OutOfMemory();
+            return NULL;
+        }
+    }
+#elif defined(__SOLARIS__)
+    const char *path = getexecname();
+    if ((path != NULL) && (path[0] == '/')) { /* must be absolute path... */
+        retval = SDL_strdup(path);
+        if (!retval) {
+            SDL_OutOfMemory();
+            return NULL;
+        }
+    }
+#endif
+
+    /* is a Linux-style /proc filesystem available? */
+    if (!retval && (access("/proc", F_OK) == 0)) {
+#if defined(__FREEBSD__)
+        retval = readSymLink("/proc/curproc/file");
+#elif defined(__NETBSD__)
+        retval = readSymLink("/proc/curproc/exe");
+#else
+        retval = readSymLink("/proc/self/exe");  /* linux. */
+#endif
+        if (retval == NULL) {
+            /* older kernels don't have /proc/self ... try PID version... */
+            char path[64];
+            const int rc = (int) SDL_snprintf(path, sizeof(path),
+                                              "/proc/%llu/exe",
+                                              (unsigned long long) getpid());
+            if ( (rc > 0) && (rc < sizeof(path)) ) {
+                retval = readSymLink(path);
+            }
+        }
+    }
+
+    /* If we had access to argv[0] here, we could check it for a path,
+        or troll through $PATH looking for it, too. */
+
+    if (retval != NULL) { /* chop off filename. */
+        char *ptr = SDL_strrchr(retval, '/');
+        if (ptr != NULL) {
+            *(ptr+1) = '\0';
+        } else {  /* shouldn't happen, but just in case... */
+            SDL_free(retval);
+            retval = NULL;
+        }
+    }
+
+    if (retval != NULL) {
+        /* try to shrink buffer... */
+        char *ptr = (char *) SDL_realloc(retval, strlen(retval) + 1);
+        if (ptr != NULL)
+            retval = ptr;  /* oh well if it failed. */
+    }
+
+    return retval;
+}
+
+char *
+SDL_GetPrefPath(const char *org, const char *app)
+{
+    /*
+     * We use XDG's base directory spec, even if you're not on Linux.
+     *  This isn't strictly correct, but the results are relatively sane
+     *  in any case.
+     *
+     * http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
+     */
+    const char *envr = SDL_getenv("XDG_DATA_HOME");
+    const char *append;
+    char *retval = NULL;
+    char *ptr = NULL;
+    size_t len = 0;
+
+    if (!envr) {
+        /* You end up with "$HOME/.local/share/Game Name 2" */
+        envr = SDL_getenv("HOME");
+        if (!envr) {
+            /* we could take heroic measures with /etc/passwd, but oh well. */
+            SDL_SetError("neither XDG_DATA_HOME nor HOME environment is set");
+            return NULL;
+        }
+        append = "/.local/share/";
+    } else {
+        append = "/";
+    }
+
+    len = SDL_strlen(envr);
+    if (envr[len - 1] == '/')
+        append += 1;
+
+    len += SDL_strlen(append) + SDL_strlen(org) + SDL_strlen(app) + 3;
+    retval = (char *) SDL_malloc(len);
+    if (!retval) {
+        SDL_OutOfMemory();
+        return NULL;
+    }
+
+    SDL_snprintf(retval, len, "%s%s%s/%s/", envr, append, org, app);
+
+    for (ptr = retval+1; *ptr; ptr++) {
+        if (*ptr == '/') {
+            *ptr = '\0';
+            if (mkdir(retval, 0700) != 0 && errno != EEXIST)
+                goto error;
+            *ptr = '/';
+        }
+    }
+    if (mkdir(retval, 0700) != 0 && errno != EEXIST) {
+error:
+        SDL_SetError("Couldn't create directory '%s': '%s'", retval, strerror(errno));
+        SDL_free(retval);
+        return NULL;
+    }
+
+    return retval;
+}
+
+#endif /* SDL_FILESYSTEM_UNIX */
+
+/* vi: set ts=4 sw=4 expandtab: */