Re: Feature Request: define sighandler_t

[Bruno Haible]

Hi Markus,

> the man-page signal(2) tells me (at least on my system):
> 
>         typedef void (*sighandler_t)(int);
> 
>         The use of sighandler_t is a GNU extension.  ...
>
> Could you define sighandler_t in the signal package iff _GNU_SOURCE is 
> defined?

In gnulib, we tend to make GNU extensions available unconditionally but
possibly in a separate module. But I don't see the point of having an
extra module 'signal-gnu', since this GNU extension does not conflict with
POSIX. So here's a proposed patch:


2011-05-03  Bruno Haible  <address@hidden>

        signal: Define sighandler_t.
        * lib/signal.in.h (sighandler_t): New type.
        * m4/signal_h.m4 (gl_SIGNAL_H): Require AC_USE_SYSTEM_EXTENSIONS. Test
        whether sighandler_t is defined.
        (gl_SIGNAL_H_DEFAULTS): Initialize HAVE_SIGHANDLER_T.
        * modules/signal (Depends-on): Add extensions.
        (Makefile.am): Substitute HAVE_SIGHANDLER_T.
        * doc/posix-headers/signal.texi: Mention the problem with sighandler_t.
        Suggested by Markus Steinborn <address@hidden>.

--- doc/posix-headers/signal.texi.orig  Tue May  3 22:57:03 2011
+++ doc/posix-headers/signal.texi       Tue May  3 22:17:21 2011
@@ -28,6 +28,11 @@
 @item
 The macro @code{SA_NODEFER} is not defined on some platforms:
 Interix 3.5.
address@hidden
+The type @code{sighandler_t} (a GNU extension) is not defined on most non-glibc
+platforms:
+MacOS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11,
+IRIX 6.5, OSF/1 5.1, Solaris 11 2010-11, Cygwin, mingw, Interix 3.5, BeOS.
 @end itemize
 
 Portability problems not fixed by Gnulib:
--- lib/signal.in.h.orig        Tue May  3 22:57:03 2011
+++ lib/signal.in.h     Tue May  3 22:18:57 2011
@@ -66,6 +66,20 @@
 # endif
 #endif
 
+/* Define sighandler_t, the type of signal handlers.  A GNU extension.  */
+#if address@hidden@
+# ifdef __cplusplus
+extern "C" {
+# endif
+# if !GNULIB_defined_sighandler_t
+typedef void (*sighandler_t) (int);
+#  define GNULIB_defined_sighandler_t 1
+# endif
+# ifdef __cplusplus
+}
+# endif
+#endif
+
 
 #if @GNULIB_SIGNAL_H_SIGPIPE@
 # ifndef SIGPIPE
--- m4/signal_h.m4.orig Tue May  3 22:57:03 2011
+++ m4/signal_h.m4      Tue May  3 22:13:56 2011
@@ -1,4 +1,4 @@
-# signal_h.m4 serial 11
+# signal_h.m4 serial 12
 dnl Copyright (C) 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -8,14 +8,22 @@
 [
   AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
   gl_NEXT_HEADERS([signal.h])
+
 # AIX declares sig_atomic_t to already include volatile, and C89 compilers
 # then choke on 'volatile sig_atomic_t'.  C99 requires that it compile.
   AC_CHECK_TYPE([volatile sig_atomic_t], [],
     [HAVE_TYPE_VOLATILE_SIG_ATOMIC_T=0], [[
 #include <signal.h>
     ]])
+
   AC_REQUIRE([AC_TYPE_UID_T])
 
+  dnl Persuade glibc <signal.h> to define sighandler_t.
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_TYPE([sighandler_t], [], [HAVE_SIGHANDLER_T=0], [[
+#include <signal.h>
+    ]])
+
   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[#include <signal.h>
@@ -46,4 +54,5 @@
                                AC_SUBST([HAVE_STRUCT_SIGACTION_SA_SIGACTION])
   HAVE_TYPE_VOLATILE_SIG_ATOMIC_T=1;
                                AC_SUBST([HAVE_TYPE_VOLATILE_SIG_ATOMIC_T])
+  HAVE_SIGHANDLER_T=1;         AC_SUBST([HAVE_SIGHANDLER_T])
 ])
--- modules/signal.orig Tue May  3 22:57:03 2011
+++ modules/signal      Tue May  3 22:56:47 2011
@@ -10,6 +10,7 @@
 c++defs
 include_next
 warn-on-use
+extensions
 
 configure.ac:
 gl_SIGNAL_H
@@ -35,6 +36,7 @@
              -e 's|@''HAVE_SIGACTION''@|$(HAVE_SIGACTION)|g' \
              -e 
's|@''HAVE_STRUCT_SIGACTION_SA_SIGACTION''@|$(HAVE_STRUCT_SIGACTION_SA_SIGACTION)|g'
 \
              -e 
's|@''HAVE_TYPE_VOLATILE_SIG_ATOMIC_T''@|$(HAVE_TYPE_VOLATILE_SIG_ATOMIC_T)|g' \
+             -e 's|@''HAVE_SIGHANDLER_T''@|$(HAVE_SIGHANDLER_T)|g' \
              -e '/definitions of _GL_FUNCDECL_RPL/r $(CXXDEFS_H)' \
              -e '/definition of _GL_ARG_NONNULL/r $(ARG_NONNULL_H)' \
              -e '/definition of _GL_WARN_ON_USE/r $(WARN_ON_USE_H)' \
-- 
In memoriam Zbigniew Iwański <http://en.wikipedia.org/wiki/Henryk_Iwański>