
 Procomm stack overflow patch:

 Symptoms:
     Procomm v. 2.42 when running on PC DOS 3.2 and MS DOS 3.x
 (some versions) will hang if CTRL-BREAK is pressed.  The message
 "stack overflow" will be emitted as well as possibly some garbage
 before the computer "locks up."

 Cure: (Patching procedure)
 With a copy of your procomm.exe file (not the original of course) do:

     RENAME PROCOMM.EXE PROCOMM.BIN
     DEBUG PROCOMM.BIN
     E 83D 90 90 90
     W
     Q
     RENAME PROCOMM.BIN PROCOMM.EXE

 The above procedure assumes procomm.exe is in the current directory
 and debug is loadable (in current dir, or in a dir in PATH).  If
 anything happens which is not understood, simply omit the W command
 above (which writes to disk) and use Q (to quit) instead.

 Technical details:
     Procomm v. 2.42 has a stack checker which is called on
 function entry to insure sufficient stack space for the function to
 execute.  PC DOS 3.2 and some MS DOS 3.x versions have an "improved"
 stack management service which insures that each new hardware
 interrupt which occurs is given a new stack to use in its interrupt
 service routine.  The size of these stacks and their number are
 settable with the CONFIG.SYS option STACKS=n,s (number, size).

     The "stack overflow" error discovered by procomm occurs
 because DOS, in response to the CTRL-BREAK interrupt, has switched
 stacks to one from the DOS stack pool, and Procomm is assuming its own
 stack is still in use.  The limits used in the stack check routine
 fail because the DOS stacks are normally much smaller (512 bytes by
 default) than the stack used by Procomm.

     The easiest way to solve the disagreement about stack
 ownership is to remove the call to the stack checking routine from the
 interrupt handler for CTRL-BREAK.  The above patch does exactly this.
 Procomm is otherwise happy to use the DOS supplied stack since
 servicing the BREAK request does not require lots of stack space.

     There may be another option for DOS 3.3 users:  It is possible
 with DOS 3.3 to disable the DOS stack swapping by putting STACKS=0 in
 the CONFIG.SYS file.  I have not tried this, but my understanding of
 the problem indicates this should also work.

     Gordon W. Ross              Phone: (617) 271-3205
     The MITRE Corporation       ARPA: linus!gwr@MITRE-BEDFORD
     Bedford, MA  01730          UUCP: decvax!linus!gwr

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