* unix/tkUnixEvent.c (TkpCloseDisplay): Don't

	test for XCloseIM bug when the XFree86 version
	is newer than 4.0 since the layout of the
	XIM structure has changed. The check is not
	needed for newer XFree86 releases since
	the bug we are checking for was fixed in
	the 4.2.99.2 release. [Bug 755530]

1 files changed, 40 insertions, 10 deletions

diff --git a/unix/tkUnixEvent.c b/unix/tkUnixEvent.c
index eeaa481..de250a1 100644
--- a/unix/tkUnixEvent.c
+++ b/unix/tkUnixEvent.c
@@ -9,7 +9,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkUnixEvent.c,v 1.11 2003/01/10 20:23:17 jenglish Exp $
+ * RCS: @(#) $Id: tkUnixEvent.c,v 1.12 2003/07/02 09:22:45 mdejong Exp $
  */
 
 #include "tkInt.h"
@@ -29,7 +29,7 @@ static Tcl_ThreadDataKey dataKey;
 #if defined(TK_USE_INPUT_METHODS) && defined(PEEK_XCLOSEIM)
 /*
  * Structure used to peek into internal XIM data structure.
- * Enabled only on systems where we are sure it works.
+ * This is only known to work with XFree86.
  */
 struct XIMPeek {
     void *junk1, *junk2;
@@ -185,17 +185,47 @@ TkpCloseDisplay(dispPtr)
 #endif
     if (dispPtr->inputMethod) {
 	/*
-	 * This caused core dumps on some systems (Solaris 2.3 1/6/95).
-	 * The most likely cause of this is a bug in X that accesses
-	 * memory that was already deallocated inside XCloseIM().
-	 * One can work around this issue by making sure a XDestroyIC()
-	 * gets invoked for each XCreateIC().
+	 * Calling XCloseIM with an input context that has not
+	 * been freed can cause a crash. This crash has been
+	 * reproduced under Linux systems with XFree86 3.3
+	 * and may have also been seen under Solaris 2.3.
+	 * The crash is caused by a double free of memory
+	 * inside the X library. Memory that was already
+	 * deallocated may be accessed again inside XCloseIM.
+	 * This bug can be avoided by making sure that a
+	 * call to XDestroyIC is made for each XCreateIC call.
+	 * This bug has been fixed in XFree86 4.2.99.2.
+	 * The internal layout of the XIM structure changed
+	 * in the XFree86 4.2 release so the test should
+	 * not be run for with these new releases.
 	 */
 
 #if defined(TK_USE_INPUT_METHODS) && defined(PEEK_XCLOSEIM)
-	struct XIMPeek *peek = (struct XIMPeek *) dispPtr->inputMethod;
-	if (peek->ic_chain != NULL)
-	    panic("input contexts not freed before XCloseIM");
+	int do_peek = 0;
+	struct XIMPeek *peek;
+
+	if (strstr(ServerVendor(dispPtr->display), "XFree86")) {
+	    int vendrel = VendorRelease(dispPtr->display);
+	    if (vendrel < 336) {
+	        /* 3.3.4 and 3.3.5 */
+	        do_peek = 1;
+	    } else if (vendrel < 3900) {
+	        /* Other 3.3.x versions */
+	        do_peek = 1;
+	    } else if (vendrel < 40000000) {
+	        /* 4.0.x versions */
+	        do_peek = 1;
+	    } else {
+	        /* Newer than 4.0 */
+	        do_peek = 0;
+	    }
+	}
+
+	if (do_peek) {
+	    peek = (struct XIMPeek *) dispPtr->inputMethod;
+	    if (peek->ic_chain != NULL)
+	        panic("input contexts not freed before XCloseIM");
+	}
 #endif
 	XCloseIM(dispPtr->inputMethod);
     }