Tcl Source Code

The current ::tcl::Bgerror command crashes (Bus error/coredump) on Mac OS X 10.4.11 when called with empty arguments:

% info pa
8.5.2b1
% parray tcl_platform
tcl_platform(byteOrder)   = littleEndian
tcl_platform(machine)     = i386
tcl_platform(os)          = Darwin
tcl_platform(osVersion)   = 8.11.1
tcl_platform(platform)    = unix
tcl_platform(pointerSize) = 4
tcl_platform(threaded)    = 1
tcl_platform(user)        = nem
tcl_platform(wordSize)    = 4
% interp bgerror {}
::tcl::Bgerror
% tcl::Bgerror {} {}
Bus error

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fixed for 8.5.2

File Added - 269843: 1901113.patch

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Attached path implementing that
alternative fix; includes tests.
File Added: 1901113.patch

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thanks for catching this.
crashing is bad; this needs
fixing.

I think the right fix, though,
is to raise an error back to
the caller if required entries
of the return options dict are
not set.

File Added - 267826: bgerror.patch

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Looks like TclDefaultBgErrorHandlerObjCmd (in generic/tclEvent.c) doesn't check for error conditions when retrieving options from the dictionary. Notably, if the dictionary passed in doesn't contain either of the expected keys {-level, -code} then the code will crash as it attempts to access the NULL pointer returned from Tcl_DictObjGet. (The code is safe for -errorcode and -errorinfo).

I attach a patch to fix this bug, by assuming -level 0 and -code TCL_ERROR (which seem like reasonable defaults). Obviously, this command is unlikely to be called directly like this anyway, but it's a simple fix to avoid a crash condition.

Also assigning to dgp as ChangeLog has your name against last entry for this command.

Cheers,
Neil
File Added: bgerror.patch