New module 'sigpipe-die'.

5 files changed, 192 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 01c184d732..55fe08e6f3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2008-08-31  Bruno Haible  <bruno@clisp.org>
 
+	New module 'sigpipe-die'.
+	* modules/sigpipe-die: New file.
+	* lib/sigpipe-die.h: New file.
+	* lib/sigpipe-die.c: New file.
+	* MODULES.html.sh (Signal handling): Add sigpipe-die.
+
+2008-08-31  Bruno Haible  <bruno@clisp.org>
+
 	Don't override previously installed signal handlers.
 	* lib/fatal-signal.c (saved_sigactions): New variable.
 	(uninstall_handlers): Reset the signal to the saved handler, not
diff --git a/MODULES.html.sh b/MODULES.html.sh
index e35b510ee6..486b451043 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -2390,6 +2390,7 @@ func_all_modules ()
   func_module c-stack
   func_module libsigsegv
   func_module sig2str
+  func_module sigpipe-die
   func_end_table
 
   element="Internationalization functions"
diff --git a/lib/sigpipe-die.c b/lib/sigpipe-die.c
new file mode 100644
index 0000000000..bb3c8b00e6
--- /dev/null
+++ b/lib/sigpipe-die.c
@@ -0,0 +1,82 @@
+/* Report a SIGPIPE signal and exit.
+   Copyright (C) 2008 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2008.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "sigpipe-die.h"
+
+#include <signal.h>
+#include <stdlib.h>
+
+#include "error.h"
+#include "exitfail.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+void
+sigpipe_die (void)
+{
+  error (exit_failure, 0, "%s",
+	 _("error writing to a closed pipe or socket"));
+
+  /* Ensure that this function really does not return.  */
+  abort ();
+}
+
+static void (*prepare_die_hook) (void);
+
+/* This is the signal handler for SIGPIPE.  It is invoked synchronously,
+   therefore it can make library calls to malloc(), gettext(), exit() etc. -
+   although in general it is undefined behaviour to do such calls from
+   within signal handlers.  */
+static void
+sigpipe_die_handler (int sig)
+{
+  if (prepare_die_hook != NULL)
+    (*prepare_die_hook) ();
+  sigpipe_die ();
+}
+
+void
+install_sigpipe_die_handler (void (*prepare_die) (void))
+{
+  prepare_die_hook = prepare_die;
+
+  /* Install the handler.  */
+  {
+    struct sigaction action;
+
+    action.sa_handler = sigpipe_die_handler;
+    action.sa_flags = 0;
+    sigemptyset (&action.sa_mask);
+    if (sigaction (SIGPIPE, &action, NULL) >= 0)
+      {
+	/* Unblock the signal (just in case).  This is needed because if the
+	   signal was blocked in the parent process, it is also blocked in
+	   this process: the mask of blocked signals is inherited across
+	   fork/exec (except for SIGCHLD).  */
+	sigset_t sigpipe_set;
+
+	sigemptyset (&sigpipe_set);
+	sigaddset (&sigpipe_set, SIGPIPE);
+	sigprocmask (SIG_UNBLOCK, &sigpipe_set, NULL);
+      }
+  }
+}
diff --git a/lib/sigpipe-die.h b/lib/sigpipe-die.h
new file mode 100644
index 0000000000..e677943bf9
--- /dev/null
+++ b/lib/sigpipe-die.h
@@ -0,0 +1,74 @@
+/* Report a SIGPIPE signal and exit.
+   Copyright (C) 2008 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2008.  */
+
+/* SIGPIPE is the signal sent to a process calling write() on a pipe with no
+   readers.  Together with the signal, the write() call is terminated with
+   return value -1, errno = EPIPE.  Note that SIGPIPE is a *synchronous*
+   signal: it occurs only during write(), without delay (unless blocked).
+
+   The default reaction on SIGPIPE, namely terminating the process without
+   an error message, is suitable for programs which only produce output to
+   standard output and don't have side effects.
+
+   When a program has side effects, other than writing to standard output, the
+   suitable behaviour is either
+     (a) to exit with an error message
+   or - in certain cases, for example when writing to subprocesses -
+     (b) to continue the operation without writing to the pipe/socket with
+         no readers.
+
+   This file provides support for (a).
+   For (b), the program needs to know which of the output file descriptors
+   has no readers.  This is usually implemented by blocking the SIGPIPE signal
+   and handling an EPIPE error indicator in all affected library calls
+   (write(), send(), fwrite(), fflush(), fclose(), etc.).  */
+
+#ifndef _SIGPIPE_DIE_H
+#define _SIGPIPE_DIE_H
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+# ifndef __attribute__
+#  if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
+#   define __attribute__(x)
+#  endif
+# endif
+
+# ifndef ATTRIBUTE_NORETURN
+#  define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
+# endif
+
+/* Emit an error message indicating a SIGPIPE signal, and terminate the
+   process with an error code.  */
+extern void sigpipe_die (void) ATTRIBUTE_NORETURN;
+
+/* Install a SIGPIPE handler that invokes PREPARE_DIE and then emits an
+   error message and exits.  PREPARE_DIE may be NULL, meaning a no-op.  */
+extern void install_sigpipe_die_handler (void (*prepare_die) (void));
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* _SIGPIPE_DIE_H */
diff --git a/modules/sigpipe-die b/modules/sigpipe-die
new file mode 100644
index 0000000000..dc00736b11
--- /dev/null
+++ b/modules/sigpipe-die
@@ -0,0 +1,27 @@
+Description:
+Report a SIGPIPE signal and exit.
+
+Files:
+lib/sigpipe-die.h
+lib/sigpipe-die.c
+
+Depends-on:
+error
+gettext-h
+exitfail
+sigprocmask
+sigaction
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += sigpipe-die.h sigpipe-die.c
+
+Include:
+"sigpipe-die.h"
+
+License:
+GPL
+
+Maintainer:
+Bruno Haible