Re: [PATCH 03/10] pthread_sigmask: new module

[Bruno Haible]

Paul Eggert wrote:
> +  m4_ifdef([gl_THREADLIB], [
> +    AC_REQUIRE([gl_THREADLIB])
> +    if test "$gl_threads_api" = posix; then
> +      gl_save_LIBS="$LIBS"
> +      LIBS="$LIBS $LIBMULTITHREAD"
> +      AC_CHECK_FUNCS([pthread_sigmask])
> +      LIBS="$gl_save_LIBS"
> +    fi
> +  ], [
> +    AC_CHECK_FUNCS_ONCE([pthread_sigmask])
> +  ])

It is a bit dangerous to use the variable ac_cv_func_pthread_sigmask for
two different purposes: once for the availability of pthread_sigmask()
in libc, and once for its presence in -lpthread.

> +Link:
> +$(LIBMULTITHREAD)

This does not work when "$gl_threads_api" != posix.

1) On OSF/1 5.1, we turn off multithreading by default, see m4/threadlib.m4:

       case "$host_os" in
         dnl Disable multithreading by default on OSF/1, because it interferes
         dnl with fork()/exec(): When msgexec is linked with -lpthread, its
         dnl child process gets an endless segmentation fault inside execvp().

   As a consequence, LIBMULTITHREAD becomes empty. Hence a link error occurs
   in unit tests:

   cc -O     -o test-pthread_sigmask1 test-pthread_sigmask1.o libtests.a 
../gllib/libgnu.a libtests.a   
   ld:
   Unresolved:
   pthread_sigmask
   *** Exit 1

2) Similarly, when the user explicitly configures with --disable-threads.

3) Similarly, when the user explicitly configures with --enable-threads=pth.
   Then it would be wrong to use pthread_sigmask from libc; instead we need
   to use pth_sigmask or, equivalently, sigprocmask. And in this case
   LIBMULTITHREAD contains "-lpth", whereas for linking lib/pthread_sigmask.o
   no external library is necessary.


This fixes it:


2011-07-07  Bruno Haible  <address@hidden>

        pthread_sigmask: Fix link requirements on OSF/1 5.1 and with pth.
        * lib/signal.in.h (pthread_sigmask): Override if
        REPLACE_PTHREAD_SIGMASK is 1.
        * m4/signal_h.m4 (gl_SIGNAL_H_DEFAULTS): Initialize
        REPLACE_PTHREAD_SIGMASK.
        * m4/pthread_sigmask.m4 (gl_FUNC_PTHREAD_SIGMASK): Set also
        REPLACE_PTHREAD_SIGMASK. Set and substitute LIB_PTHREAD_SIGMASK.
        * modules/signal (Makefile.am): Substitute REPLACE_PTHREAD_SIGMASK.
        * modules/pthread_sigmask (Depends-on, configure.ac): Update condition.
        (Link): Set to $(LIB_PTHREAD_SIGMASK), not $(LIBMULTITHREAD).

--- lib/signal.in.h.orig        Fri Jul  8 03:53:40 2011
+++ lib/signal.in.h     Fri Jul  8 03:39:24 2011
@@ -125,12 +125,23 @@
 
 
 #if @GNULIB_PTHREAD_SIGMASK@
-# if address@hidden@
+# if @REPLACE_PTHREAD_SIGMASK@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef pthread_sigmask
+#   define pthread_sigmask rpl_pthread_sigmask
+#  endif
+_GL_FUNCDECL_RPL (pthread_sigmask, int,
+                  (int how, const sigset_t *new_mask, sigset_t *old_mask));
+_GL_CXXALIAS_RPL (pthread_sigmask, int,
+                  (int how, const sigset_t *new_mask, sigset_t *old_mask));
+# else
+#  if address@hidden@
 _GL_FUNCDECL_SYS (pthread_sigmask, int,
                   (int how, const sigset_t *new_mask, sigset_t *old_mask));
-# endif
+#  endif
 _GL_CXXALIAS_SYS (pthread_sigmask, int,
                   (int how, const sigset_t *new_mask, sigset_t *old_mask));
+# endif
 _GL_CXXALIASWARN (pthread_sigmask);
 #elif defined GNULIB_POSIXCHECK
 # undef pthread_sigmask
--- m4/pthread_sigmask.m4.orig  Fri Jul  8 03:53:40 2011
+++ m4/pthread_sigmask.m4       Fri Jul  8 03:53:31 2011
@@ -1,4 +1,4 @@
-# pthread_sigmask.m4 serial 4
+# pthread_sigmask.m4 serial 5
 dnl Copyright (C) 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,
@@ -6,21 +6,67 @@
 
 AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
 [
+  AC_CHECK_FUNCS_ONCE([pthread_sigmask])
+  LIB_PTHREAD_SIGMASK=
   m4_ifdef([gl_THREADLIB], [
     AC_REQUIRE([gl_THREADLIB])
     if test "$gl_threads_api" = posix; then
-      gl_save_LIBS="$LIBS"
-      LIBS="$LIBS $LIBMULTITHREAD"
-      AC_CHECK_FUNCS([pthread_sigmask])
-      LIBS="$gl_save_LIBS"
+      if test $ac_cv_func_pthread_sigmask = yes; then
+        dnl pthread_sigmask is available without -lpthread.
+        :
+      else
+        if test -n "$LIBMULTITHREAD"; then
+          AC_CACHE_CHECK([for pthread_sigmask in $LIBMULTITHREAD],
+            [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD],
+            [gl_save_LIBS="$LIBS"
+             LIBS="$LIBS $LIBMULTITHREAD"
+             AC_COMPILE_IFELSE(
+               [AC_LANG_PROGRAM(
+                  [[#include <pthread.h>
+                    #include <signal.h>
+                  ]],
+                  [[return pthread_sigmask (0, (sigset_t *) 0, (sigset_t *) 
0);]])
+               ],
+               [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=yes],
+               [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=no])
+             LIBS="$gl_save_LIBS"
+            ])
+          if test $gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD = yes; then
+            dnl pthread_sigmask is available with -lpthread.
+            LIB_PTHREAD_SIGMASK="$LIBMULTITHREAD"
+          else
+            dnl pthread_sigmask is not available at all.
+            HAVE_PTHREAD_SIGMASK=0
+          fi
+        else
+          dnl pthread_sigmask is not available at all.
+          HAVE_PTHREAD_SIGMASK=0
+        fi
+      fi
     else
-      ac_cv_func_pthread_sigmask=no
+      dnl pthread_sigmask may exist but does not interoperate with the chosen
+      dnl multithreading facility.
+      dnl If "$gl_threads_api" = pth, we could use the function pth_sigmask,
+      dnl but it is equivalent to sigprocmask, so we choose to emulate
+      dnl pthread_sigmask with sigprocmask also in this case. This yields fewer
+      dnl link dependencies.
+      if test $ac_cv_func_pthread_sigmask = yes; then
+        REPLACE_PTHREAD_SIGMASK=1
+      else
+        HAVE_PTHREAD_SIGMASK=0
+      fi
+    fi
+  ] ,[
+    dnl If module 'threadlib' is not in use, assume all programs will be
+    dnl single-threaded.
+    if test $ac_cv_func_pthread_sigmask = yes; then
+      REPLACE_PTHREAD_SIGMASK=1
+    else
+      HAVE_PTHREAD_SIGMASK=0
     fi
-  ], [
-    AC_CHECK_FUNCS_ONCE([pthread_sigmask])
   ])
-
-  if test $ac_cv_func_pthread_sigmask = no; then
-    HAVE_PTHREAD_SIGMASK=0
-  fi
+  AC_SUBST([LIB_PTHREAD_SIGMASK])
+  dnl We don't need a variable LTLIB_PTHREAD_SIGMASK, because when
+  dnl "$gl_threads_api" = posix, $LTLIBMULTITHREAD and $LIBMULTITHREAD are the
+  dnl same: either both empty or both "-lpthread".
 ])
--- m4/signal_h.m4.orig Fri Jul  8 03:53:40 2011
+++ m4/signal_h.m4      Fri Jul  8 03:39:24 2011
@@ -1,4 +1,4 @@
-# signal_h.m4 serial 15
+# signal_h.m4 serial 16
 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,
@@ -73,4 +73,5 @@
   HAVE_TYPE_VOLATILE_SIG_ATOMIC_T=1;
                                AC_SUBST([HAVE_TYPE_VOLATILE_SIG_ATOMIC_T])
   HAVE_SIGHANDLER_T=1;         AC_SUBST([HAVE_SIGHANDLER_T])
+  REPLACE_PTHREAD_SIGMASK=0;   AC_SUBST([REPLACE_PTHREAD_SIGMASK])
 ])
--- modules/pthread_sigmask.orig        Fri Jul  8 03:53:40 2011
+++ modules/pthread_sigmask     Fri Jul  8 03:46:57 2011
@@ -7,11 +7,11 @@
 
 Depends-on:
 signal
-sigprocmask     [test $HAVE_PTHREAD_SIGMASK = 0]
+sigprocmask     [test $HAVE_PTHREAD_SIGMASK = 0 || test 
$REPLACE_PTHREAD_SIGMASK = 1]
 
 configure.ac:
 gl_FUNC_PTHREAD_SIGMASK
-if test $HAVE_PTHREAD_SIGMASK = 0; then
+if test $HAVE_PTHREAD_SIGMASK = 0 || test $REPLACE_PTHREAD_SIGMASK = 1; then
   AC_LIBOBJ([pthread_sigmask])
 fi
 gl_SIGNAL_MODULE_INDICATOR([pthread_sigmask])
@@ -22,7 +22,7 @@
 <signal.h>
 
 Link:
-$(LIBMULTITHREAD)
+$(LIB_PTHREAD_SIGMASK)
 
 License:
 LGPLv2+
--- modules/signal.orig Fri Jul  8 03:53:40 2011
+++ modules/signal      Fri Jul  8 03:39:24 2011
@@ -40,6 +40,7 @@
              -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''@|$(HAVE_SIGHANDLER_T)|g' \
+             -e 's|@''REPLACE_PTHREAD_SIGMASK''@|$(REPLACE_PTHREAD_SIGMASK)|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 Georges Mandel <http://en.wikipedia.org/wiki/Georges_Mandel>