Restore the tcl_platform(threaded) variable.

3 files changed, 13 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index 668108b..96f8d1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -34,13 +34,6 @@
 	* library/dde/pkgIndex.tcl   Use [::tcl::pkgconfig get debug] instead
 	* library/reg/pkgIndex.tcl   of [info exists ::tcl_platform(debug)]
 
-	***POTENTIAL INCOMPATIBILITY***
-	The variables $tcl_platform(debug) and $tcl_platform(threaded) no
-	longer exist. They don't belong in the tcl_platform array, were never
-	documented, disturbed the platform-1.1 test, $tcl_platform(debug) was
-	only available on Windows anyway, and TIP #59 provides a much better
-	alternative.
-
 2012-04-10  Donal K. Fellows  <dkf@users.sf.net>
 
 	* generic/tcl.h (TCL_DEPRECATED_API): [Bug 2458976]: Added macro that
diff --git a/generic/tclBasic.c b/generic/tclBasic.c
index 21fb2e2..e09ea1e 100644
--- a/generic/tclBasic.c
+++ b/generic/tclBasic.c
@@ -928,6 +928,17 @@ Tcl_CreateInterp(void)
 	    TclPrecTraceProc, NULL);
     TclpSetVariables(interp);
 
+#ifdef TCL_THREADS
+    /*
+     * The existence of the "threaded" element of the tcl_platform array
+     * indicates that this particular Tcl shell has been compiled with threads
+     * turned on. Using "info exists tcl_platform(threaded)" a Tcl script can
+     * introspect on the interpreter level of thread safety.
+     */
+
+    Tcl_SetVar2(interp, "tcl_platform", "threaded", "1", TCL_GLOBAL_ONLY);
+#endif
+
     /*
      * Register Tcl's version number.
      * TIP #268: Full patchlevel instead of just major.minor
diff --git a/tests/platform.test b/tests/platform.test
index 33c96ba..8cb8dcd 100644
--- a/tests/platform.test
+++ b/tests/platform.test
@@ -18,6 +18,8 @@ testConstraint testWinCPUID [llength [info commands testwincpuid]]
 
 test platform-1.1 {TclpSetVariables: tcl_platform} {
     interp create i
+    i eval {catch {unset tcl_platform(debug)}}
+    i eval {catch {unset tcl_platform(threaded)}}
     set result [i eval {lsort [array names tcl_platform]}]
     interp delete i
     set result