1 files changed, 92 insertions, 0 deletions
diff --git a/lib/pthread_sigmask.c b/lib/pthread_sigmask.c
new file mode 100644
index 0000000..1281075
--- /dev/null
+++ b/lib/pthread_sigmask.c
@@ -0,0 +1,92 @@
+/* POSIX compatible signal blocking for threads.
+   Copyright (C) 2011-2023 Free Software Foundation, Inc.
+
+   This file 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 file 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, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <signal.h>
+
+#include <errno.h>
+#include <stddef.h>
+
+#if PTHREAD_SIGMASK_INEFFECTIVE
+# include <string.h>
+#endif
+
+#if PTHREAD_SIGMASK_UNBLOCK_BUG
+# include <unistd.h>
+#endif
+
+int
+pthread_sigmask (int how, const sigset_t *new_mask, sigset_t *old_mask)
+#undef pthread_sigmask
+{
+#if HAVE_PTHREAD_SIGMASK
+  int ret;
+
+# if PTHREAD_SIGMASK_INEFFECTIVE
+  sigset_t omask, omask_copy;
+  sigset_t *old_mask_ptr = &omask;
+  sigemptyset (&omask);
+  /* Add a signal unlikely to be blocked, so that OMASK_COPY
+     is unlikely to match the actual mask.  */
+  sigaddset (&omask, SIGILL);
+  memcpy (&omask_copy, &omask, sizeof omask);
+# else
+  sigset_t *old_mask_ptr = old_mask;
+# endif
+
+  ret = pthread_sigmask (how, new_mask, old_mask_ptr);
+
+# if PTHREAD_SIGMASK_INEFFECTIVE
+  if (ret == 0)
+    {
+      /* Detect whether pthread_sigmask is currently ineffective.
+         Don't cache the information: libpthread.so could be dynamically
+         loaded after the program started and after pthread_sigmask was
+         called for the first time.  */
+      if (memcmp (&omask_copy, &omask, sizeof omask) == 0
+          && pthread_sigmask (1729, &omask_copy, NULL) == 0)
+        {
+          /* pthread_sigmask is currently ineffective.  The program is not
+             linked to -lpthread.  So use sigprocmask instead.  */
+          return (sigprocmask (how, new_mask, old_mask) < 0 ? errno : 0);
+        }
+
+      if (old_mask)
+        memcpy (old_mask, &omask, sizeof omask);
+    }
+# endif
+# if PTHREAD_SIGMASK_FAILS_WITH_ERRNO
+  if (ret == -1)
+    return errno;
+# endif
+# if PTHREAD_SIGMASK_UNBLOCK_BUG
+  if (ret == 0
+      && new_mask != NULL
+      && (how == SIG_UNBLOCK || how == SIG_SETMASK))
+    {
+      /* Give the OS the opportunity to raise signals that were pending before
+         the pthread_sigmask call and have now been unblocked.  */
+      usleep (1);
+    }
+# endif
+  return ret;
+#else
+  int ret = sigprocmask (how, new_mask, old_mask);
+  return (ret < 0 ? errno : 0);
+#endif
+}