[vlc-devel] [PATCH v3 07/19] compat: Add sigwait dummy for NaCl

[Dennis Hamester]

From: Julian Scheel <julian at jusst.de>

Implement a sigwait dummy for NaCl, which relies on:
- NaCl does never send SIGPIPE to to apps (see
https://codereview.chromium.org/288063004/)
- VLC uses sigwait exclusively to wait for SIGPIPE

If sigwait is asked to wait for anything else than SIGPIPE it will run
into an assertion failure, so that breakage would not be silent.

Signed-off-by: Julian Scheel <julian at jusst.de>
---
 compat/sigwait.c     | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 configure.ac         |  2 +-
 include/vlc_fixups.h |  9 +++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 compat/sigwait.c

diff --git a/compat/sigwait.c b/compat/sigwait.c
new file mode 100644
index 0000000000..e5a082d2d6
--- /dev/null
+++ b/compat/sigwait.c
@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * sigwait.c: POSIX sigwait() replacement
+ *****************************************************************************
+ * Copyright © 2017 VLC authors and VideoLAN
+ *
+ * Author: Julian Scheel <julian at jusst.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#ifdef __native_client__
+/* NaCl has no working sigwait, but SIGPIPE, for which vlc uses sigwait
+ * currently, is never generated in NaCl. So for SIGPIPE it's safe to instantly
+ * return, for all others run into an assertion. */
+
+#include <assert.h>
+#include <signal.h>
+
+int sigwait(const sigset_t *set, int *sig)
+{
+    sigset_t s = *set;
+    if (sigemptyset(&s))
+        return 0;
+    assert(sigismember(&s, SIGPIPE));
+    sigdelset(&s, SIGPIPE);
+    assert(sigemptyset(&s));
+
+    *sig = SIGPIPE;
+    return 0;
+}
+#else
+# error sigwait not implemented on your platform!
+#endif
diff --git a/configure.ac b/configure.ac
index eb7bc0fb0c..42cf0d3e7d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -595,7 +595,7 @@ need_libc=false
 
 dnl Check for usual libc functions
 AC_CHECK_FUNCS([daemon fcntl flock fstatvfs fork getenv getpwuid_r isatty lstat memalign mkostemp mmap open_memstream openat pread posix_fadvise posix_madvise setlocale stricmp strnicmp strptime tdestroy uselocale pthread_cond_timedwait_monotonic_np pthread_condattr_setclock])
-AC_REPLACE_FUNCS([atof atoll dirfd fdopendir ffsll flockfile fsync getdelim getpid lldiv memrchr nrand48 poll posix_memalign recvmsg rewind sendmsg setenv strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tfind timegm timespec_get strverscmp])
+AC_REPLACE_FUNCS([atof atoll dirfd fdopendir ffsll flockfile fsync getdelim getpid lldiv memrchr nrand48 poll posix_memalign recvmsg rewind sendmsg setenv sigwait strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tfind timegm timespec_get strverscmp])
 AC_REPLACE_FUNCS([gettimeofday])
 AC_CHECK_FUNC(fdatasync,,
   [AC_DEFINE(fdatasync, fsync, [Alias fdatasync() to fsync() if missing.])
diff --git a/include/vlc_fixups.h b/include/vlc_fixups.h
index eff661de3d..1380ac2ee7 100644
--- a/include/vlc_fixups.h
+++ b/include/vlc_fixups.h
@@ -107,6 +107,15 @@ extern "C" {
 # define VLC_NOTHROW
 #endif
 
+/* signal.h */
+#if !defined(HAVE_SIGWAIT) && defined(__native_client__)
+/* NaCl does not define sigwait in signal.h. We need to include it here to
+ * define sigwait, because sigset_t is allowed to be either an integral or a
+ * struct. */
+#include <signal.h>
+int sigwait(const sigset_t *set, int *sig);
+#endif
+
 /* stddef.h */
 #if !defined (__cplusplus) && !defined (HAVE_MAX_ALIGN_T)
 typedef struct {
-- 
2.12.0