A Stack From a Dump

DW SS:BP L10
001f:000014e6  1550 00f1 000f 02e8 18ae 0000 0000 0000
001f:000014f6  0000 0000 0000 0000 0000 0000 0000 0000

The first word, which is addressed by the current value in the
BP register, is the near address of the next stack frame, 1550.

The next two words are a far return address, with the offset to
the left of the selector.  The return is to address F:F1.

The words following the return address are the parameters, if any
were passed.  There is no direct way to tell from the stack how
many parameters were passed, or expected.  To see the next frame,

DW 1550 L 10
001f:00001550  0000 0300 000f 0001 1560 001f 156e 001f
001f:00001560  1568 001f 0000 0000 4544 4f4d 0000 15c6

In this stack frame, the BP chain pointer is zero.  This usually
means that you have found all of the frames on this stack.

The return address for this frame is F:300. The parameters
seem to be an integer, 1, and three far addresses, 1F:1560,
1F:156e, and 1F:1568. A little further inspection shows that
the third address 1F:1568 is pointed to by the first, which is
highly unusual.  Actually, this is the stack frame received by 'main'.
Main's parameters are as follows:


  1 .
 an   integer ,   which   tells   it   how   many   strings   were   found   on   the   command   line

  2 .
 the   far   address   of   a   list   of   addresses ,   each   of   which   points   to   one   of
the   strings

  3 .
 the   far   address   of   a   second   list   of   addresses ,   each   of   which   points   to
an   environment   variable .   This   list   is   terminated   with   a   NULL   POINTER ,   a   far
address   in   which   both   the   selector   and   offset   are   zero .

Let ' s   look   at   them . 1F : 1560   has   the   address   1f : 1568 .   Near   addresses   default   to   the
last   selector   used ,   so   we   are   not   required   to   supply   it   every   time .

DA   1568
# 001f : 00001568   DEMO

Right ,   the   name   of   the   program   was   the   first   string   on   the   command   line .
The   first   parameter   indicates   that   there   is   only   one   string .


Let ' s   look   at   a   few   of   the   environment   variables .

DW   156E   L8
001f : 0000156e    15c6   001f   15da   001f   1608   001f   161f   001f

This   gets   us   four   far   addresses .   To   see   them   all   with   only   one
input   line ,   use   the   semicolon   as   a   command   delimiter   and   type   away .

DA   15C6 ; DA   15DA ; DA1608 ; DA   161F
001f : 000015c6   WP _ OBJHANDLE = 132739
001f : 000015da   AUTOSTART = PROGRAMS , TASKLIST , FOLDERS , LAUNCHPAD
001f : 00001608   BOOKSHELF = C : \ OS2 \ BOOK ;
001f : 0000161f   COMSPEC = C : \ OS2 \ CMD . EXE

Notice   that   the   tools   are   not   very   particular   about   spaces   in   the   commands .

Lastly ,   to   see   the   local   data   for   the   failing   routine ,
DW   SS : SP   BP - 2
001f : 000014be    02e8   18ae   00e3   2910   0017   0060   0017   0000
001f : 000014ce    0004   0017   c8cf   0000   0030   c949   c85a   c8cf
001f : 000014de    0002   0000   00e6   1488
and   now   you   have   it ,   displayed   above .