Below is a list of the bugs that are fixed by patch 3 for Tcl 7.4
(Tcl 7.4p3):

9/27/95 (bug fix) The "format" command didn't check for huge or negative
width specifiers, which could cause core dumps. (JO)

9/27/95 (bug fix) Core dumps could occur if an interactive command typed
to tclsh returned a very long result for tclsh to print out.  The bug is
actually in printf (in Solaris 2.3 and 2.4, at least);  switched to use
puts instead.  (JO)

10/1/95 (bug fix) "exec" command wasn't always generating the
"child process exited abnormally" message when it should have.  (JO)