Provide sem_* functions

Some applications, instead of using pthread_mutex_t, use anonymous
semaphores (sem_init) for locking.

Signed-off-by: Julien Danjou <julien@danjou.info>

2 files changed, 104 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index b7f0698..ffccea9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,7 +31,7 @@ fi
 
 
 PKG_CONFIG_LIBS=
-AC_CHECK_FUNCS([pthread_self pthread_mutex_init pthread_mutex_destroy pthread_mutex_lock pthread_mutex_unlock pthread_cond_init pthread_cond_destroy pthread_cond_wait pthread_cond_signal pthread_cond_broadcast pthread_equal],
+AC_CHECK_FUNCS([pthread_self pthread_mutex_init pthread_mutex_destroy pthread_mutex_lock pthread_mutex_unlock pthread_cond_init pthread_cond_destroy pthread_cond_wait pthread_cond_signal pthread_cond_broadcast pthread_equal sem_init sem_destroy sem_wait sem_trywait],
 	       [], [PKG_CONFIG_LIBS='-L${libdir} -lpthread-stubs'])
 AC_SUBST([PKG_CONFIG_LIBS])
 AM_CONDITIONAL(BUILD_LIB, test "x$PKG_CONFIG_LIBS" != x)
diff --git a/stubs.c b/stubs.c
index d267fa6..c553e4d 100644
--- a/stubs.c
+++ b/stubs.c
@@ -25,6 +25,8 @@
  */
 
 #include <pthread.h>
+#include <errno.h>
+#include <semaphore.h>
 #include "config.h"
 
 #ifndef HAVE_PTHREAD_SELF
@@ -126,6 +128,51 @@ int pthread_equal() __attribute__ ((weak, alias ("__pthread_equal_stub")));
 # endif
 #endif
 
+#ifndef HAVE_SEM_INIT
+#define NEED_SEM_INIT_STUB
+# ifdef SUPPORT_ATTRIBUTE_ALIAS
+int sem_init() __attribute__ ((weak, alias ("__sem_init_stub")));
+# else
+#  pragma weak sem_init = __sem_init_stub
+# endif
+#endif
+
+#ifndef HAVE_SEM_DESTROY
+#define NEED_ZERO_STUB
+# ifdef SUPPORT_ATTRIBUTE_ALIAS
+int sem_destroy() __attribute__ ((weak, alias ("__pthread_zero_stub")));
+# else
+#  pragma weak sem_destroy = __sem_destroy_stub
+# endif
+#endif
+
+#ifndef HAVE_SEM_WAIT
+#define NEED_SEM_WAIT_STUB
+# ifdef SUPPORT_ATTRIBUTE_ALIAS
+int sem_wait() __attribute__ ((weak, alias ("__sem_wait_stub")));
+# else
+#  pragma weak sem_wait = __sem_wait_stub
+# endif
+#endif
+
+#ifndef HAVE_SEM_TRYWAIT
+#define NEED_SEM_TRYWAIT_STUB
+# ifdef SUPPORT_ATTRIBUTE_ALIAS
+int sem_trywait() __attribute__ ((weak, alias ("__sem_trywait_stub")));
+# else
+#  pragma weak sem_trywait = __sem_trywait_stub
+# endif
+#endif
+
+#ifndef HAVE_SEM_POST
+#define NEED_SEM_POST_STUB
+# ifdef SUPPORT_ATTRIBUTE_ALIAS
+int sem_post() __attribute__ ((weak, alias ("__sem_post_stub")));
+# else
+#  pragma weak sem_post = __sem_post_stub
+# endif
+#endif
+
 #ifdef NEED_ZERO_STUB
 static int __pthread_zero_stub()
 {
@@ -139,3 +186,59 @@ static int __pthread_equal_stub(pthread_t t1, pthread_t t2)
     return (t1 == t2);
 }
 #endif
+
+#ifdef NEED_SEM_INIT_STUB
+static int __sem_init_stub(sem_t *_sem, int pshared, unsigned int value)
+{
+    unsigned int *sem = (unsigned int *) _sem;
+    if (pshared) {
+	errno = ENOSYS;
+	return -1;
+    }
+
+    if (sizeof(sem_t) < sizeof(unsigned int)) {
+	errno = ENOSYS;
+	return -1;
+    }
+
+    *sem = value;
+    return 0;
+}
+#endif
+
+#ifdef NEED_SEM_WAIT_STUB
+static int __sem_wait_stub(sem_t *_sem)
+{
+    unsigned int *sem = (unsigned int *) _sem;
+    if (!*sem) {
+	/* Not available, simulate a blocking sem_wait */
+	pause();
+	errno = EINTR;
+	return -1;
+    }
+    *sem--;
+    return 0;
+}
+#endif
+
+#ifdef NEED_SEM_TRYWAIT_STUB
+static int __sem_trywait_stub(sem_t *_sem)
+{
+    unsigned int *sem = (unsigned int *) _sem;
+    if (!*sem) {
+	errno = EAGAIN;
+	return -1;
+    }
+    *sem--;
+    return 0;
+}
+#endif
+
+#ifdef NEED_SEM_POST_STUB
+static int __sem_post_stub(sem_t *_sem)
+{
+    unsigned int *sem = (unsigned int *) _sem;
+    *sem++;
+    return 0;
+}
+#endif