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DBX(1)		    UNIX Programmer's Manual		   DBX(1)



N\bNA\bAM\bME\bE
     dbx - debugger

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     d\bdb\bbx\bx [ -\b-r\br ] [ -\b-i\bi ] [ -\b-k\bk ] [ -\b-I\bI _\bd_\bi_\br ] [ -\b-c\bc _\bf_\bi_\bl_\be ] [ _\bo_\bb_\bj_\bf_\bi_\bl_\be [
     _\bc_\bo_\br_\be_\bd_\bu_\bm_\bp ]]

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     _\bD_\bb_\bx is a tool for source level debugging and execution of
     programs under UNIX.  The _\bo_\bb_\bj_\bf_\bi_\bl_\be is an object file produced
     by a compiler with the appropriate flag (usually ``-g'')
     specified to produce symbol information in the object file.
     Currently, _\bc_\bc(1), _\bf_\b7_\b7(1), _\bp_\bc(1), and the DEC Western
     Research Laboratory Modula-2 compiler, _\bm_\bo_\bd(l), produce the
     appropriate source information.  The machine level facili-
     ties of _\bd_\bb_\bx can be used on any program.

     The object file contains a symbol table that includes the
     name of the all the source files translated by the compiler
     to create it.  These files are available for perusal while
     using the debugger.

     If a file named ``core'' exists in the current directory or
     a _\bc_\bo_\br_\be_\bd_\bu_\bm_\bp file is specified, _\bd_\bb_\bx can be used to examine the
     state of the program when it faulted.

     If the file ``.dbxinit'' exists in the current directory
     then the debugger commands in it are executed.  _\bD_\bb_\bx also
     checks for a ``.dbxinit'' in the user's home directory if
     there isn't one in the current directory.

     The command line options and their meanings are:

     -\b-r\br      Execute _\bo_\bb_\bj_\bf_\bi_\bl_\be immediately.  If it terminates suc-
	     cessfully _\bd_\bb_\bx exits.  Otherwise the reason for ter-
	     mination will be reported and the user offered the
	     option of entering the debugger or letting the pro-
	     gram fault.  _\bD_\bb_\bx will read from ``/dev/tty'' when -\b-r\br
	     is specified and standard input is not a terminal.

     -\b-i\bi      Force _\bd_\bb_\bx to act as though standard input is a ter-
	     minal.

     -\b-k\bk      Map memory addresses, useful for kernel debugging.

     -\b-I\bI _\bd_\bi_\br  Add _\bd_\bi_\br to the list of directories that are searched
	     when looking for a source file.  Normally _\bd_\bb_\bx looks
	     for source files in the current directory and in the
	     directory where _\bo_\bb_\bj_\bf_\bi_\bl_\be is located.  The directory
	     search path can also be set with the u\bus\bse\be command.

     -\b-c\bc _\bf_\bi_\bl_\be Execute the _\bd_\bb_\bx commands in the _\bf_\bi_\bl_\be before reading



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DBX(1)		    UNIX Programmer's Manual		   DBX(1)



	     from standard input.


     Unless -\b-r\br is specified, _\bd_\bb_\bx just prompts and waits for a
     command.

     E\bEx\bxe\bec\bcu\but\bti\bio\bon\bn a\ban\bnd\bd T\bTr\bra\bac\bci\bin\bng\bg C\bCo\bom\bmm\bma\ban\bnd\bds\bs


     r\bru\bun\bn [_\ba_\br_\bg_\bs] [<\b< _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [>\b> _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
     r\bre\ber\bru\bun\bn [_\ba_\br_\bg_\bs] [<\b< _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [>\b> _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
	  Start executing _\bo_\bb_\bj_\bf_\bi_\bl_\be, passing _\ba_\br_\bg_\bs as command line
	  arguments; <\b< or >\b> can be used to redirect input or out-
	  put in the usual manner.  When r\bre\ber\bru\bun\bn is used without
	  any arguments the previous argument list is passed to
	  the program; otherwise it is identical to r\bru\bun\bn.  If
	  _\bo_\bb_\bj_\bf_\bi_\bl_\be has been written since the last time the sym-
	  bolic information was read in, _\bd_\bb_\bx will read in the new
	  information.

     t\btr\bra\bac\bce\be [i\bin\bn _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     t\btr\bra\bac\bce\be _\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     t\btr\bra\bac\bce\be _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn [i\bin\bn _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     t\btr\bra\bac\bce\be _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn a\bat\bt _\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     t\btr\bra\bac\bce\be _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be [i\bin\bn _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
	  Have tracing information printed when the program is
	  executed.  A number is associated with the command that
	  is used to turn the tracing off (see the d\bde\bel\ble\bet\bte\be com-
	  mand).

	  The first argument describes what is to be traced.  If
	  it is a _\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br, then the line is printed
	  immediately prior to being executed.	Source line
	  numbers in a file other than the current one must be
	  preceded by the name of the file in quotes and a colon,
	  e.g.	"mumble.p":17.

	  If the argument is a procedure or function name then
	  every time it is called, information is printed telling
	  what routine called it, from what source line it was
	  called, and what parameters were passed to it.  In
	  addition, its return is noted, and if it's a function
	  then the value it is returning is also printed.

	  If the argument is an _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn with an a\bat\bt clause then
	  the value of the expression is printed whenever the
	  identified source line is reached.

	  If the argument is a variable then the name and value
	  of the variable is printed whenever it changes.  Execu-
	  tion is substantially slower during this form of trac-
	  ing.



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	  If no argument is specified then all source lines are
	  printed before they are executed.  Execution is sub-
	  stantially slower during this form of tracing.

	  The clause ``i\bin\bn _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn'' restricts tracing
	  information to be printed only while executing inside
	  the given procedure or function.

	  _\bC_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn is a boolean expression and is evaluated
	  prior to printing the tracing information; if it is
	  false then the information is not printed.

     s\bst\bto\bop\bp i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn
     s\bst\bto\bop\bp a\bat\bt _\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     s\bst\bto\bop\bp i\bin\bn _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
     s\bst\bto\bop\bp _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be [i\bif\bf _\bc_\bo_\bn_\bd_\bi_\bt_\bi_\bo_\bn]
	  Stop execution when the given line is reached, pro-
	  cedure or function called, variable changed, or condi-
	  tion true.

     s\bst\bta\bat\btu\bus\bs [>\b> _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
	  Print out the currently active t\btr\bra\bac\bce\be and s\bst\bto\bop\bp commands.

     d\bde\bel\ble\bet\bte\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd-_\bn_\bu_\bm_\bb_\be_\br ...
	  The traces or stops corresponding to the given numbers
	  are removed.	The numbers associated with traces and
	  stops are printed by the s\bst\bta\bat\btu\bus\bs command.

     c\bca\bat\btc\bch\bh _\bn_\bu_\bm_\bb_\be_\br
     c\bca\bat\btc\bch\bh _\bs_\bi_\bg_\bn_\ba_\bl-_\bn_\ba_\bm_\be
     i\big\bgn\bno\bor\bre\be _\bn_\bu_\bm_\bb_\be_\br
     i\big\bgn\bno\bor\bre\be _\bs_\bi_\bg_\bn_\ba_\bl-_\bn_\ba_\bm_\be
	  Start or stop trapping a signal before it is sent to
	  the program.	This is useful when a program being
	  debugged handles signals such as interrupts.	A signal
	  may be specified by number or by a name (e.g., SIGINT).
	  Signal names are case insensitive and the ``SIG'' pre-
	  fix is optional.  By default all signals are trapped
	  except SIGCONT, SIGCHILD, SIGALRM and SIGKILL.

     c\bco\bon\bnt\bt _\bi_\bn_\bt_\be_\bg_\be_\br
     c\bco\bon\bnt\bt _\bs_\bi_\bg_\bn_\ba_\bl-_\bn_\ba_\bm_\be
	  Continue execution from where it stopped.  If a signal
	  is specified, the process continues as though it
	  received the signal.	Otherwise, the process is contin-
	  ued as though it had not been stopped.

     Execution cannot be continued if the process has ``fin-
     ished'', that is, called the standard procedure ``exit''.
     _\bD_\bb_\bx does not allow the process to exit, thereby letting the
     user to examine the program state.




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     s\bst\bte\bep\bp Execute one source line.

     n\bne\bex\bxt\bt Execute up to the next source line.  The difference
	  between this and s\bst\bte\bep\bp is that if the line contains a
	  call to a procedure or function the s\bst\bte\bep\bp command will
	  stop at the beginning of that block, while the n\bne\bex\bxt\bt
	  command will not.

     r\bre\bet\btu\bur\brn\bn [_\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be]
	  Continue until a return to _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be is executed, or
	  until the current procedure returns if none is speci-
	  fied.

     c\bca\bal\bll\bl _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be(_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs)
	  Execute the object code associated with the named pro-
	  cedure or function.


     P\bPr\bri\bin\bnt\bti\bin\bng\bg V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs a\ban\bnd\bd E\bEx\bxp\bpr\bre\bes\bss\bsi\bio\bon\bns\bs


     Names are resolved first using the static scope of the
     current function, then using the dynamic scope if the name
     is not defined in the static scope.  If static and dynamic
     searches do not yield a result, an arbitrary symbol is
     chosen and the message ``[using _\bq_\bu_\ba_\bl_\bi_\bf_\bi_\be_\bd _\bn_\ba_\bm_\be]'' is
     printed.  The name resolution procedure may be overridden by
     qualifying an identifier with a block name, e.g.,
     ``_\bm_\bo_\bd_\bu_\bl_\be._\bv_\ba_\br_\bi_\ba_\bb_\bl_\be''.  For C, source files are treated as
     modules named by the file name without ``.c''.

     Expressions are specified with an approximately common sub-
     set of C and Pascal (or equivalently Modula-2) syntax.
     Indirection can be denoted using either a prefix ``*'' or a
     postfix ``^'' and array expressions are subscripted by
     brackets (``[ ]'').  The field reference operator (``.'')
     can be used with pointers as well as records, making the C
     operator ``->'' unnecessary (although it is supported).

     Types of expressions are checked; the type of an expression
     may be overridden by using ``_\bt_\by_\bp_\be-_\bn_\ba_\bm_\be(_\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn)''.  When
     there is no corresponding named type the special constructs
     ``&_\bt_\by_\bp_\be-_\bn_\ba_\bm_\be'' and ``$$_\bt_\ba_\bg-_\bn_\ba_\bm_\be'' can be used to represent a
     pointer to a named type or C structure tag.


     a\bas\bss\bsi\big\bgn\bn _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be =\b= _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn
	  Assign the value of the expression to the variable.

     d\bdu\bum\bmp\bp [_\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be] [>\b> _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
	  Print the names and values of variables in the given
	  procedure, or the current one if none is specified.  If



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DBX(1)		    UNIX Programmer's Manual		   DBX(1)



	  the procedure given is ``.'', then the all active vari-
	  ables are dumped.

     p\bpr\bri\bin\bnt\bt _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn [,\b, _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn ...]
	  Print out the values of the expressions.

     w\bwh\bha\bat\bti\bis\bs _\bn_\ba_\bm_\be
	  Print the declaration of the given name, which may be
	  qualified with block names as above.

     w\bwh\bhi\bic\bch\bh _\bi_\bd_\be_\bn_\bt_\bi_\bf_\bi_\be_\br
	  Print the full qualification of the given identifer,
	  i.e.	the outer blocks that the identifier is associ-
	  ated with.

     u\bup\bp [_\bc_\bo_\bu_\bn_\bt]
     d\bdo\bow\bwn\bn [_\bc_\bo_\bu_\bn_\bt]
	  Move the current function, which is used for resolving
	  names, up or down the stack _\bc_\bo_\bu_\bn_\bt levels.  The default
	  _\bc_\bo_\bu_\bn_\bt is 1.

     w\bwh\bhe\ber\bre\be
	  Print out a list of the active procedures and function.

     w\bwh\bhe\ber\bre\bei\bis\bs _\bi_\bd_\be_\bn_\bt_\bi_\bf_\bi_\be_\br
	  Print the full qualification of all the symbols whose
	  name matches the given identifier.  The order in which
	  the symbols are printed is not meaningful.


     A\bAc\bcc\bce\bes\bss\bsi\bin\bng\bg S\bSo\bou\bur\brc\bce\be F\bFi\bil\ble\bes\bs


     /_\br_\be_\bg_\bu_\bl_\ba_\br _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn[/]
     ?_\br_\be_\bg_\bu_\bl_\ba_\br _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn[?]
	  Search forward or backward in the current source file
	  for the given pattern.

     e\bed\bdi\bit\bt [_\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
     e\bed\bdi\bit\bt _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn-_\bn_\ba_\bm_\be
	  Invoke an editor on _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be or the current source file
	  if none is specified.  If a _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be or _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn name
	  is specified, the editor is invoked on the file that
	  contains it.	Which editor is invoked by default
	  depends on the installation.	The default can be over-
	  ridden by setting the environment variable EDITOR to
	  the name of the desired editor.

     f\bfi\bil\ble\be [_\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
	  Change the current source file name to _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.  If
	  none is specified then the current source file name is
	  printed.



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     f\bfu\bun\bnc\bc [_\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn]
	  Change the current function.	If none is specified then
	  print the current function.  Changing the current func-
	  tion implicitly changes the current source file to the
	  one that contains the function; it also changes the
	  current scope used for name resolution.

     l\bli\bis\bst\bt [_\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br [,\b, _\bs_\bo_\bu_\br_\bc_\be-_\bl_\bi_\bn_\be-_\bn_\bu_\bm_\bb_\be_\br]]
     l\bli\bis\bst\bt _\bp_\br_\bo_\bc_\be_\bd_\bu_\br_\be/_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
	  List the lines in the current source file from the
	  first line number to the second inclusive.  If no lines
	  are specified, the next 10 lines are listed.	If the
	  name of a procedure or function is given lines _\bn-_\bk to
	  _\bn+_\bk are listed where _\bn is the first statement in the
	  procedure or function and _\bk is small.

     u\bus\bse\be _\bd_\bi_\br_\be_\bc_\bt_\bo_\br_\by-_\bl_\bi_\bs_\bt
	  Set the list of directories to be searched when looking
	  for source files.


     C\bCo\bom\bmm\bma\ban\bnd\bd A\bAl\bli\bia\bas\bse\bes\bs a\ban\bnd\bd V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs


     a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be _\bn_\ba_\bm_\be
     a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be ``_\bs_\bt_\br_\bi_\bn_\bg''
     a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be (_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs) ``_\bs_\bt_\br_\bi_\bn_\bg''
	  When commands are processed, dbx first checks to see if
	  the word is an alias for either a command or a string.
	  If it is an alias, then dbx treats the input as though
	  the corresponding string (with values substituted for
	  any parameters) had been entered.  For example, to
	  define an alias ``rr'' for the command ``rerun'', one
	  can say

		  alias rr rerun

	  To define an alias called ``b'' that sets a stop at a
	  particular line one can say

		  alias b(x) ``stop at x''

	  Subsequently, the command ``b(12)'' will expand to
	  ``stop at 12''.

     s\bse\bet\bt _\bn_\ba_\bm_\be [= _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn]
	  The s\bse\bet\bt command defines values for debugger variables.
	  The names of these variables cannot conflict with names
	  in the program being debugged, and are expanded to the
	  corresponding expression within other commands.  The
	  following variables have a special meaning:




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	     $frame
		  Setting this variable to an address causes dbx
		  to use the stack frame pointed to by the
		  address for doing stack traces and accessing
		  local variables.  This facility is of particu-
		  lar use for kernel debugging.

	     $hexchars
	     $hexints
	     $hexoffsets
	     $hexstrings
		  When set, dbx prints out out characters,
		  integers, offsets from registers, or character
		  pointers respectively in hexadecimal.

	     $listwindow
		  The value of this variable specifies the number
		  of lines to list around a function or when the
		  l\bli\bis\bst\bt command is given without any parameters.
		  Its default value is 10.

	     $mapaddrs
		  Setting (unsetting) this variable causes dbx to
		  start (stop) mapping addresses.  As with
		  ``$frame'', this is useful for kernel debug-
		  ging.

	     $unsafecall
	     $unsafeassign
		  When ``$unsafecall'' is set, strict type check-
		  ing is turned off for arguments to subroutine
		  or function calls (_\be._\bg. in the c\bca\bal\bll\bl statement).
		  When ``$unsafeassign'' is set, strict type
		  checking between the two sides of an a\bas\bss\bsi\big\bgn\bn
		  statement is turned off.  These variables
		  should be used only with great care, because
		  they severely limit dbx's usefulness for
		  detecting errors.

     u\bun\bna\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be
	  Remove the alias with the given name.

     u\bun\bns\bse\bet\bt _\bn_\ba_\bm_\be
	  Delete the debugger variable associated with _\bn_\ba_\bm_\be.











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     M\bMa\bac\bch\bhi\bin\bne\be L\bLe\bev\bve\bel\bl C\bCo\bom\bmm\bma\ban\bnd\bds\bs


     t\btr\bra\bac\bce\bei\bi [_\ba_\bd_\bd_\br_\be_\bs_\bs] [i\bif\bf _\bc_\bo_\bn_\bd]
     t\btr\bra\bac\bce\bei\bi [_\bv_\ba_\br_\bi_\ba_\bb_\bl_\be] [a\bat\bt _\ba_\bd_\bd_\br_\be_\bs_\bs] [i\bif\bf _\bc_\bo_\bn_\bd]
     s\bst\bto\bop\bpi\bi [_\ba_\bd_\bd_\br_\be_\bs_\bs] [i\bif\bf _\bc_\bo_\bn_\bd]
     s\bst\bto\bop\bpi\bi [a\bat\bt] [_\ba_\bd_\bd_\br_\be_\bs_\bs] [i\bif\bf _\bc_\bo_\bn_\bd]
	  Turn on tracing or set a stop using a machine instruc-
	  tion address.

     s\bst\bte\bep\bpi\bi
     n\bne\bex\bxt\bti\bi
	  Single step as in s\bst\bte\bep\bp or n\bne\bex\bxt\bt, but do a single
	  instruction rather than source line.

     _\ba_\bd_\bd_\br_\be_\bs_\bs ,\b,_\ba_\bd_\bd_\br_\be_\bs_\bs/\b/ [_\bm_\bo_\bd_\be]
     _\ba_\bd_\bd_\br_\be_\bs_\bs /\b/ [_\bc_\bo_\bu_\bn_\bt] [_\bm_\bo_\bd_\be]
	  Print the contents of memory starting at the first
	  _\ba_\bd_\bd_\br_\be_\bs_\bs and continuing up to the second _\ba_\bd_\bd_\br_\be_\bs_\bs or
	  until _\bc_\bo_\bu_\bn_\bt items are printed.  If the address is
	  ``.'', the address following the one printed most
	  recently is used.  The _\bm_\bo_\bd_\be specifies how memory is to
	  be printed; if it is omitted the previous mode speci-
	  fied is used.  The initial mode is ``X''.  The follow-
	  ing modes are supported:

	  i\bi    print the machine instruction
	  d\bd    print a short word in decimal
	  D\bD    print a long word in decimal
	  o\bo    print a short word in octal
	  O\bO    print a long word in octal
	  x\bx    print a short word in hexadecimal
	  X\bX    print a long word in hexadecimal
	  b\bb    print a byte in octal
	  c\bc    print a byte as a character
	  s\bs    print a string of characters terminated by a null
	       byte
	  f\bf    print a single precision real number
	  g\bg    print a double precision real number


     Symbolic addresses are specified by preceding the name with
     an ``&''.	Registers are denoted by ``$rN'' where N is the
     number of the register.  Addresses may be expressions made
     up of other addresses and the operators ``+'', ``-'', and
     indirection (unary ``*'').









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     M\bMi\bis\bsc\bce\bel\bll\bla\ban\bne\beo\bou\bus\bs C\bCo\bom\bmm\bma\ban\bnd\bds\bs


     g\bgr\bri\bip\bpe\be
	  Invoke a mail program to send a message to the person
	  in charge of _\bd_\bb_\bx.

     h\bhe\bel\blp\bp Print out a synopsis of _\bd_\bb_\bx commands.

     q\bqu\bui\bit\bt Exit _\bd_\bb_\bx.

     s\bsh\bh _\bc_\bo_\bm_\bm_\ba_\bn_\bd-_\bl_\bi_\bn_\be
	  Pass the command line to the shell for execution.  The
	  SHELL environment variable determines which shell is
	  used.

     s\bso\bou\bur\brc\bce\be _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
	  Read _\bd_\bb_\bx commands from the given _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.

F\bFI\bIL\bLE\bES\bS
     a.out		 object file
     .dbxinit		 initial commands

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     cc(1), f77(1), pc(1), mod(l)

C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS
     _\bD_\bb_\bx suffers from the same ``multiple include'' malady as did
     _\bs_\bd_\bb.  If you have a program consisting of a number of object
     files and each is built from source files that include
     header files, the symbolic information for the header files
     is replicated in each object file.  Since about one debugger
     start-up is done for each link, having the linker (ld) re-
     organize the symbol information would not save much time,
     though it would reduce some of the disk space used.

     This problem is an artifact of the unrestricted semantics of
     #include's in C; for example an include file can contain
     static declarations that are separate entities for each file
     in which they are included.  However, even with Modula-2
     there is a substantial amount of duplication of symbol
     information necessary for inter-module type checking.

     Some problems remain with the support for individual
     languages.  Fortran problems include: inability to assign to
     logical, logical*2, complex and double complex variables;
     inability to represent parameter constants which are not
     type integer or real; peculiar representation for the values
     of dummy procedures (the value shown for a dummy procedure
     is actually the first few bytes of the procedure text; to
     find the location of the procedure, use ``&'' to take the
     address of the variable).



Printed 7/9/88		January 12, 1986			9