Integrate change #9646 from maintperl into mainline.

add note about ithreads and Thread.pm

p4raw-link: @9646 on //depot/maint-5.6/perl: 17a9312cad5ed64ba042d3290b6b96c0c0cf8f59

p4raw-id: //depot/perl@9648
p4raw-integrated: from //depot/maint-5.6/perl@9647 'merge in'
	ext/Thread/Thread.pm (@7247..) ext/Thread/Thread.xs (@9547..)

2 files changed, 16 insertions, 1 deletions

diff --git a/ext/Thread/Thread.pm b/ext/Thread/Thread.pm
index 3a545482a9..3deef813ab 100644
--- a/ext/Thread/Thread.pm
+++ b/ext/Thread/Thread.pm
@@ -12,6 +12,15 @@ $VERSION = "1.0";
 
 Thread - manipulate threads in Perl (EXPERIMENTAL, subject to change)
 
+=head1 CAVEAT
+
+The Thread extension requires Perl to be built in a particular way to
+enable the older 5.005 threading model.  Just to confuse matters, there
+is an alternate threading model known as "ithreads" that does NOT
+support this extension.  If you are using a binary distribution such
+as ActivePerl that is built with ithreads support, this extension CANNOT
+be used.
+
 =head1 SYNOPSIS
 
     use Thread;
diff --git a/ext/Thread/Thread.xs b/ext/Thread/Thread.xs
index f87e7c4a31..cb2e395051 100644
--- a/ext/Thread/Thread.xs
+++ b/ext/Thread/Thread.xs
@@ -322,7 +322,13 @@ newthread (pTHX_ SV *startsv, AV *initargs, char *classname)
 
     return sv;
 #else
-    croak("No threads in this perl");
+#  ifdef USE_ITHREADS
+    croak("This perl was built for \"ithreads\", which currently does not support Thread.pm.\n"
+	  "Run \"perldoc Thread\" for more information");
+#  else
+    croak("This perl was not built with support for 5.005-style threads.\n"
+	  "Run \"perldoc Thread\" for more information");
+#  endif
     return &PL_sv_undef;
 #endif
 }