Bug #16053 for Tk: gtk2 > 2.8.0 apps are causing segfaults in Tk , with readv(3, [{"_GTK_LOAD_ICONTHEMES", 20},

Guest via RT <bug-Tk@rt.cpan.org> writes: Show quoted text
As one toolkit is crashing another my guess is that GTK has put something in a X Property that per/Tk does not like. As it is a SEGV I am guessing that something that has been marked as a 32-bit property (or perhaps perk/Tk has _assumed_ is 32 bit) has a number of bytes which isn't a multiple of 4. Is file handle 3 that is being readv()ed the X socket (further back strace). Or as it SEGVs if by chance you can get a backtrace from gdb

Hmm, If I have read Xproto.h correctly read(4, "\241 b\16\1\0\300\0\306\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 32) = 32 That is a ClientMessage Event \2xx is Event \41 = Decimal 33 = ClientMessage ' ' is just a padding byte b\16 is sequence number \1\0\300\0 is Window \0\306\1\0 is Atom which identifies Message So will take a look at what Tk does when it gets unexpected ClientMessage-s.

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I've applied this patch, and it doesn't fix the problem. According to gdb, the crash is inside Tk_HandleEvent().

Latest patch has been confirmed as a fix.

On Thu Dec 29 07:48:14 2005, NI-S wrote: Show quoted text
I added the patch. However, I still get a Segmentation Fault within 20 button clicks of the short script I am pasting below, on at least two Linux variants. Doing a Google search for "Segmentation fault after destroying non-dependent window" will reveal that this is a problem on a number of Linux platforms. It works fine on Windows. #!/usr/bin/perl -w # File test_pop_up_a_message.pl use Tk; use strict; our $answer = "okay"; ############ sub response { my ($we_top, $button_response) = @_; $we_top->destroy; $answer = $button_response; } ############ sub pop_up_a_message { my ($message) = @_; my $okay_button; my $exit_button; print("Can allways see\n"); my $we_top = new MainWindow; print("Cannot see if Segmentation fault\n"); $we_top->Label ( -text => $message)->pack(); #......... $okay_button = $we_top->Button( -text => 'Okay', -command => [ \&response, $we_top, 'okay' ] )->pack(); #......... $exit_button = $we_top->Button( -text => 'Exit', -command => [ \&response, $we_top, 'exit' ] )->pack(); #......... $we_top->MainLoop; } ############ my $message = ""; my $count = 1; while ($answer eq "okay") { $message = " On at least Slackware and Mandriva, Perl 5.8.7 or 5.8.8, this code will\n" . " get a Segmentation fault within 20 clicks of Okay \n " . $count++ . "\n"; pop_up_a_message($message); print ("You pressed $answer\n"); }

On Fri Feb 24 06:41:12 2006, guest wrote: Show quoted text
Hi, I think you posted this bug under the wrong category. This bug thread was caused by Gtk2 apps interfering with Tk. Your problem dosn't even mention Gtk2. By the way, I ran your script without any segfaults, many times. I'm using linux on a customized slackware.

On Fri Feb 24 06:41:12 2006, guest wrote: Show quoted text
This is the output of a debugging Tk, with the tkEvent.c patch applied, when I run you script. When running with a debugging Tk, with plain Perl 5.8.7 with original patch of tkEvent.c:986 if(interp){...} At segfault: ##################################################### Program received signal SIGSEGV, Segmentation fault. 0xb7d1861f in Tk_GetOptionValue () from /usr/lib/perl5/site_perl/5.8.7/i686-linux-thread-multi-ld/auto/Tk/Tk.so (gdb) bt #0 0xb7d1861f in Tk_GetOptionValue () from /usr/lib/perl5/site_perl/5.8.7/i686-linux-thread-multi-ld/auto/Tk/Tk.so #1 0xb7cc723a in FrameWidgetObjCmd () from /usr/lib/perl5/site_perl/5.8.7/i686-linux-thread-multi-ld/auto/Tk/Tk.so #2 0xb7c95d06 in Call_Tk (info=0x83d87b8, items=3, args=0x825a184) at tkGlue.c:2283 #3 0xb7c9729c in XStoWidget (my_perl=0x8154f68, cv=0x8290534) at tkGlue.c:2662 #4 0x080c6aa1 in Perl_pp_entersub () #5 0x080bf309 in Perl_runops_standard () #6 0x08064a7b in perl_run () #7 0x0805fe5d in main () (gdb) q ######################################################## Maybe Nick Ing Simmons will know what changes need to be made.

On Wed Mar 01 11:11:35 2006, guest wrote: Show quoted text
Well Matthias' response was directed to the original bug, which is the bug originally discussed in this thread. I posted this problem to the Gtk buglist, and they responded, that no matter if Gtk was involved in causing the segfault, it was a Tk problem....because Tk should not be responding to Gtk's window manager signals. That problem was apparently fixed to my (and others) satisfaction by the patch. Since patching, I've not seen any segfaults, and I run alot of Tk and Gtk2 code. Your program does indeed raise the spector that this bug is not totally fixed....i.e. there probably is another place in the code which needs patching. I cannot easily see where, from the results of my backtrace. It will take the mind of Nick Ing Simmons, with his more intimate knowledge. Furthermore, your particular code segfaults on it's own, not as a result of something in a gtk2 app. In the original bug, a button press in a Gtk2 app, would kill ALL running Tk programs. Your code snippet only kills itself, so it is a different type of problem. Additionally, your example snippet itself may be causing it, by the way it is written. All I can say, is that I have not seen any problem with this bug since the patch, with the exception of your code. I also posted it on comp.lang.perl.tk, and no one else is complaining about noticing it. Sooo........in summary, I think it is a different bug, (although there is a similarity in the gtk_load_iconthemes appearing in the strace output before the crash. The main differences between your new bug and the original is.... 1. Your code kills itself and only itself, where in the original bug, a button click in a gtk2 app would kill ALL running Tk apps. 2. Nobody is reporting seeing the bug, except when running your test code.

There is a pertinent reason why the test code given is relevent. Besides just surfacing the bug. I have an application wherein the user makes a choice from a Perl/Tk pop up menu. Once a choice is made, the pop up is destroyed and something then runs in the background. When the user chosen task is done running, one of a number of different pop ups could happen, depending upon the results. One could be a pop up wherein the user is asked if he wants to run it again. Different home grown Perl modules have different pop ups. Most are very simple informational messages but they need to be popped up, and then destroyed when the user clicks an Okay button. Hence I really do need to be able to create a pop up in a routine, destroy it, create another one from another routine, destroy it, and so on. That is why the test code really does reflect the problem space. It runs just fine on Windows, by the way. No problems whatsoever on Windows. It is only the Linux varients that have the problem. I cannot imagine that Tk really has a problem with the concept of having a popup attempted multiple times. This has to be a bug that can be resolved. I do a careful cleanup each time the user clicks the Okay button by explicitly using the "destroy" method, such as $we_top->destroy. Isn't that supposed to destory MainWindow and take care of any needed cleanup? Shouldn't I then be free to call a routine that might (or might not) pop up a new message? Is there something I am missing?

Guest via RT <bug-Tk@rt.cpan.org> writes: Show quoted text
I am not following all this yet, but the bug fix cannot stop Gtk sending the message - so message will still be read from the X socket, which is what the strace fragment shows. The bug fix causes Tk to ignore the message. The message likely gets sent by the window manager when a new top level window is created.