1 /*****************************************************************************
2 * override.c: overridden function calls for VLC media player
3 *****************************************************************************
4 * Copyright (C) 2010 RĂ©mi Denis-Courmont
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU Lesser General Public License as published by
8 * the Free Software Foundation; either version 2.1 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
19 *****************************************************************************/
28 void vlc_enable_override (void);
30 #if defined (__GNUC__) \
31 && (defined (__ELF__) && !defined (__sun__))
32 /* Solaris crashes on printf("%s", NULL); which is legal, but annoying. */
40 #ifdef HAVE_EXECINFO_H
41 # include <execinfo.h>
45 # undef HAVE_BACKTRACE
48 static bool override = false;
50 static void vlc_reset_override (void)
55 void vlc_enable_override (void)
58 pthread_atfork (NULL, NULL, vlc_reset_override);
61 static void vlogbug (unsigned *pc, const char *level, const char *func,
62 const char *fmt, va_list ap)
65 const size_t framec = 5;
68 backtrace (framev, framec);
74 fprintf (stderr, "%s: call to %s(", level, func);
75 vfprintf (stderr, fmt, ap);
76 fputs (")\n", stderr);
79 backtrace_symbols_fd (framev + 2, framec - 2, STDERR_FILENO);
85 static void logbug (unsigned *pc, const char *level, const char *func,
91 vlogbug (pc, level, func, fmt, ap);
95 static void *getsym (const char *name)
97 void *sym = dlsym (RTLD_NEXT, name);
100 fprintf (stderr, "Cannot resolve symbol %s: %s\n", name,
107 #define LOG(level, ...) \
109 static unsigned counter = 0; \
110 logbug(&counter, level, __func__, __VA_ARGS__); \
113 /* Evil non-standard GNU C macro ;)
115 * statement-expression
117 #define CALL(func, ...) \
118 ({ typeof (func) *sym = getsym ( # func); sym (__VA_ARGS__); })
122 * "Conforming multi-threaded applications shall not use the environ variable
123 * to access or modify any environment variable while any other thread is
124 * concurrently modifying any environment variable." -- POSIX.
126 * Some evil libraries modify the environment. We currently ignore the calls as
127 * they could crash the process. This may cause funny behaviour though. */
128 int putenv (char *str)
132 LOG("Blocked", "\"%s\"", str);
135 return CALL(putenv, str);
138 int setenv (const char *name, const char *value, int overwrite)
142 LOG("Blocked", "\"%s\", \"%s\", %d", name, value, overwrite);
145 return CALL(setenv, name, value, overwrite);
148 int unsetenv (const char *name)
152 LOG("Blocked", "\"%s\"", name);
155 return CALL(unsetenv, name);
159 /*** Pseudo random numbers ***
161 * The C PRNG is not thread-safe (and generally sucks, the POSIX 48-bits PRNG
162 * is much better as a reproducible non-secure PRNG). To work around this, we
163 * force evil callers to serialize. This makes the call safe, but fails to
164 * preserve reproducibility of the number sequence (which usually does not
169 pthread_mutex_t lock;
171 } prng = { PTHREAD_MUTEX_INITIALIZER, 0, };
173 void srand (unsigned int seed)
175 pthread_mutex_lock (&prng.lock);
176 LOG("Warning", "%d", seed);
178 pthread_mutex_unlock (&prng.lock);
185 pthread_mutex_lock (&prng.lock);
187 ret = rand_r (&prng.seed);
188 pthread_mutex_unlock (&prng.lock);
197 static bool blocked_signal (int num)
212 void (*signal (int signum, void (*handler) (int))) (int)
216 if (handler != SIG_IGN && handler != SIG_DFL)
218 if (!blocked_signal (signum))
220 /* For our blocked signals, the handler won't matter much... */
221 if (handler == SIG_DFL)
222 LOG("Warning", "%d, SIG_DFL", signum, handler);
224 return CALL(signal, signum, handler);
226 LOG("Blocked", "%d, %p", signum, handler);
230 int sigaction (int signum, const struct sigaction *act, struct sigaction *old)
232 if (override && act != NULL)
234 if ((act->sa_flags & SA_SIGINFO)
235 || (act->sa_handler != SIG_IGN && act->sa_handler != SIG_DFL))
237 if (act->sa_handler == SIG_DFL)
238 LOG("Warning", "%d, %p, SIG_DFL", signum, act);
240 return CALL(sigaction, signum, act, old);
242 LOG("Blocked", "%d, %p, %p", signum, act, old);
249 * setlocale() is not thread-safe and has a tendency to crash other threads as
250 * quite many libc and libintl calls depend on the locale.
251 * Use uselocale() instead for thread-safety.
255 char *setlocale (int cat, const char *locale)
257 if (override && locale != NULL)
259 LOG("Blocked", "%d, \"%s\"", cat, locale);
262 return CALL(setlocale, cat, locale);
266 /* strerror() is not thread-safe in theory (POSIX), nor in practice (glibc).
267 * This caused quite nasty crashes in the history of VLC/Linux. */
268 char *strerror (int val)
272 static const char msg[] =
273 "Error message unavailable (use strerror_r instead of strerror)!";
274 LOG("Blocked", "%d", val);
277 return CALL(strerror, val);
281 #ifdef HAVE_X11_XLIB_H
282 # include <X11/Xlib.h>
284 static pthread_mutex_t xlib_lock = PTHREAD_MUTEX_INITIALIZER;
286 int (*XSetErrorHandler (int (*handler) (Display *, XErrorEvent *)))
287 (Display *, XErrorEvent *)
291 int (*ret) (Display *, XErrorEvent *);
293 pthread_mutex_lock (&xlib_lock);
294 LOG("Error", "%p", handler);
295 ret = CALL(XSetErrorHandler, handler);
296 pthread_mutex_unlock (&xlib_lock);
299 return CALL(XSetErrorHandler, handler);
302 int (*XSetIOErrorHandler (int (*handler) (Display *))) (Display *)
306 int (*ret) (Display *);
308 pthread_mutex_lock (&xlib_lock);
309 LOG("Error", "%p", handler);
310 ret = CALL(XSetIOErrorHandler, handler);
311 pthread_mutex_unlock (&xlib_lock);
314 return CALL(XSetIOErrorHandler, handler);
318 void vlc_enable_override (void)