[FYI 1/4] {testsuite-work} test defs: work around weird ksh behaviour w.r.t. signal handling

[Stefano Lattarini]

* tests/defs (is_blocked_signal): Use perl to determine whether a
signal is trapped, since trying to do it portably within the shell
means opening a nasty can of worms.

For more information and background, see:
 <http://lists.gnu.org/archive/html/bug-autoconf/2011-09/msg00004.html>
 
<http://mail.opensolaris.org/pipermail/ksh93-integration-discuss/2009-February/004121.html>
 <http://www.cons.org/cracauer/sigint.html>
---
 ChangeLog  |   11 +++++++++++
 tests/defs |   18 +++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9b98bfd..cbc6693 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2011-09-13  Stefano Lattarini  <address@hidden>
+
+       test defs: work around weird ksh behaviour w.r.t. signal handling
+       * tests/defs (is_blocked_signal): Use perl to determine whether a
+       signal is trapped, since trying to do it portably within the shell
+       means opening a nasty can of worms.
+       For more information and background, see:
+        <http://lists.gnu.org/archive/html/bug-autoconf/2011-09/msg00004.html>
+        
<http://mail.opensolaris.org/pipermail/ksh93-integration-discuss/2009-February/004121.html>
+        <http://www.cons.org/cracauer/sigint.html>
+
 2011-09-12  Stefano Lattarini  <address@hidden>
 
        tests: remove redundant line from a test script
diff --git a/tests/defs b/tests/defs
index cbeccb9..9fed42e 100644
--- a/tests/defs
+++ b/tests/defs
@@ -247,7 +247,23 @@ is_newest ()
 # return a non-zero exit status and print a proper diagnostic otherwise.
 is_blocked_signal ()
 {
-  $SHELL -c "kill -$1 \$\$; echo '$me: signal $1 seems blocked'"
+  # Use perl, since trying to do this portably in the shell can be
+  # very tricky, if not downright impossible.  For reference, see:
+  # <http://lists.gnu.org/archive/html/bug-autoconf/2011-09/msg00004.html>
+  if $PERL -w -e '
+    use strict;
+    use warnings FATAL => "all";
+    use POSIX;
+    my %oldsigaction = ();
+    sigaction('"$1"', 0, \%oldsigaction);
+    exit ($oldsigaction{"HANDLER"} eq "IGNORE" ? 0 : 77);
+  '; then
+    return 0
+  elif test $? -eq 77; then
+    return 1
+  else
+    fatal_ "couldn't determine whether signal $1 is blocked"
+  fi
 }
 
 # AUTOMAKE_run [-e STATUS] [-d DESCRIPTION] [--] [AUTOMAKE-ARGS...]
-- 
1.7.2.3