4.3BSD-Reno/share/man/cat1/dbx.0
DBX(1) UNIX Reference Manual DBX(1)
NNAAMMEE
ddbbxx - debugger
SSYYNNOOPPSSIISS
DDbbxx [--rr] [--ii] [--kk] [--II _d_i_r] [--cc _f_i_l_e] [_o_b_j_f_i_l_e [_c_o_r_e_d_u_m_p]]
DDEESSCCRRIIPPTTIIOONN
DDbbxx is a tool for source level debugging and execution of programs under
UNIX. The _o_b_j_f_i_l_e is an object file produced by a compiler with the ap-
propriate flag (usually --gg) specified to produce symbol information in
the object file. Currently, cc(1), f77(1), pc(1), and the DEC Western
Research Laboratory Modula-2 compiler, mod(l), produce the appropriate
source information. The machine level facilities of ddbbxx can be used on
any program.
The object file contains a symbol table that includes the names of 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 _c_o_r_e exists in the current directory or a _c_o_r_e_d_u_m_p file
is specified, ddbbxx can be used to examine the state of the program when it
faulted.
If the file ._d_b_x_i_n_i_t exists in the current directory then the debugger
commands in it are executed. DDbbxx also checks for a ._d_b_x_i_n_i_t in the
user's home directory if there isn't one in the current directory.
The command line options and their meanings are:
--rr Execute _o_b_j_f_i_l_e immediately. If it terminates successfully ddbbxx
exits. Otherwise the reason for termination will be reported
and the user offered the option of entering the debugger or
letting the program fault. DDbbxx will read from /_d_e_v/_t_t_y when --rr
is specified and standard input is not a terminal.
--ii Force ddbbxx to act as though standard input is a terminal.
--kk Map memory addresses, useful for kernel debugging.
--II _d_i_r Add _d_i_r to the list of directories that are searched when look-
ing for a source file. Normally ddbbxx looks for source files in
the current directory and in the directory where _o_b_j_f_i_l_e is lo-
cated. The directory search path can also be set with the uussee
command.
--cc _f_i_l_e Execute the ddbbxx commands in the _f_i_l_e before reading from stan-
dard input.
Unless --rr is specified, ddbbxx just prompts and waits for a command.
EExxeeccuuttiioonn aanndd TTrraacciinngg CCoommmmaannddss
rruunn [_a_r_g_s] [<< _f_i_l_e_n_a_m_e] [>> _f_i_l_e_n_a_m_e]
rreerruunn [_a_r_g_s] [<< _f_i_l_e_n_a_m_e] [>> _f_i_l_e_n_a_m_e]
Start executing _o_b_j_f_i_l_e, passing _a_r_g_s as command line argu-
ments; << or >> can be used to redirect input or output in the
usual manner. When rreerruunn is used without any arguments the
previous argument list is passed to the program; otherwise it
is identical to rruunn. If _o_b_j_f_i_l_e has been written since the
last time the symbolic information was read in, ddbbxx will read
in the new information.
ttrraaccee [iinn _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n] [iiff _c_o_n_d_i_t_i_o_n]
ttrraaccee _s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r [iiff _c_o_n_d_i_t_i_o_n]
ttrraaccee _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n [iinn _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n] [iiff _c_o_n_d_i_t_i_o_n]
ttrraaccee _e_x_p_r_e_s_s_i_o_n aatt _s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r [iiff _c_o_n_d_i_t_i_o_n]
ttrraaccee _v_a_r_i_a_b_l_e [iinn _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n] [iiff _c_o_n_d_i_t_i_o_n]
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 ddeelleettee command).
The first argument describes what is to be traced. If it is a
_s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r, 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 param-
eters 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 _e_x_p_r_e_s_s_i_o_n with an aatt 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. Execution is substan-
tially slower during this form of tracing.
If no argument is specified then all source lines are printed
before they are executed. Execution is substantially slower
during this form of tracing.
The clause iinn _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n restricts tracing information
to be printed only while executing inside the given procedure
or function.
_C_o_n_d_i_t_i_o_n is a boolean expression and is evaluated prior to
printing the tracing information; if it is false then the in-
formation is not printed.
ssttoopp iiff _c_o_n_d_i_t_i_o_n
ssttoopp aatt _s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r [iiff _c_o_n_d_i_t_i_o_n]
ssttoopp iinn _s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r [iiff _c_o_n_d_i_t_i_o_n]
ssttoopp _v_a_r_i_a_b_l_e [iiff _c_o_n_d_i_t_i_o_n]
Stop execution when the given line is reached, procedure or
function called, variable changed, or condition true.
ssttaattuuss [>> _f_i_l_e_n_a_m_e]
Print out the currently active ttrraaccee and ssttoopp commands.
ddeelleettee _c_o_m_m_a_n_d-_n_u_m_b_e_r ...
The traces or stops corresponding to the given numbers are
removed. The numbers associated with traces and stops are
printed by the ssttaattuuss command.
ccaattcchh _n_u_m_b_e_r
ccaattcchh _s_i_g_n_a_l-_n_a_m_e
iiggnnoorree _n_u_m_b_e_r
iiggnnoorree _s_i_g_n_a_l-_n_a_m_e
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'' prefix is optional. By default all
signals are trapped except SIGCONT, SIGCHILD, SIGALRM and
SIGKILL.
ccoonntt _i_n_t_e_g_e_r
ccoonntt _s_i_g_n_a_l-_n_a_m_e
Continue execution from where it stopped. If a signal is
specified, the process continues as though it received the
signal. Otherwise, the process is continued as though it had
not been stopped.
Execution cannot be continued if the process has ``finished'',
that is, called the standard procedure ``exit''. DDbbxx does not
allow the process to exit, thereby letting the user to examine
the program state.
sstteepp Execute one source line.
nneexxtt Execute up to the next source line. The difference between
this and sstteepp is that if the line contains a call to a pro-
cedure or function the sstteepp command will stop at the beginning
of that block, while the nneexxtt command will not.
rreettuurrnn [_p_r_o_c_e_d_u_r_e]
Continue until a return to _p_r_o_c_e_d_u_r_e is executed, or until the
current procedure returns if none is specified.
ccaallll _p_r_o_c_e_d_u_r_e (_p_a_r_a_m_e_t_e_r_s)
Execute the object code associated with the named procedure or
function.
PPrriinnttiinngg VVaarriiaabblleess aanndd EExxpprreessssiioonnss
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 Ar qualified name]''
is printed. The name resolution procedure may be overridden by qualify-
ing an identifier with a block name, e.g., ``module.variable'' For C,
source files are treated as modules named by the file name without
``.c''.
Expressions are specified with an approximately common subset of C and
Pascal (or equivalently Modula-2) syntax. Indirection can be denoted us-
ing 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 ``_t_y_p_e-_n_a_m_e (_e_x_p_r_e_s_s_i_o_n)''. When there is no
corresponding named type the special constructs ``&_t_y_p_e-_n_a_m_e'' and
``$$_t_a_g-_n_a_m_e'' can be used to represent a pointer to a named type or C
structure tag.
aassssiiggnn _v_a_r_i_a_b_l_e==_e_x_p_r_e_s_s_i_o_n
Assign the value of the expression to the variable.
dduummpp [_p_r_o_c_e_d_u_r_e] [>> _f_i_l_e_n_a_m_e]
Print the names and values of variables in the given procedure,
or the current one if none is specified. If the procedure
given is ``.'', then the all active variables are dumped.
pprriinntt _e_x_p_r_e_s_s_i_o_n [,, _e_x_p_r_e_s_s_i_o_n ...]
Print out the values of the expressions.
wwhhaattiiss _n_a_m_e
Print the declaration of the given name, which may be qualified
with block names as above.
wwhhiicchh _i_d_e_n_t_i_f_i_e_r
Print the full qualification of the given identifer, i.e. the
outer blocks that the identifier is associated with.
uupp [_c_o_u_n_t]
ddoowwnn [_c_o_u_n_t]
Move the current function, which is used for resolving names,
up or down the stack _c_o_u_n_t levels. The default _c_o_u_n_t is 1.
wwhheerree Print out a list of the active procedures and function.
wwhheerreeiiss _i_d_e_n_t_i_f_i_e_r
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.
AAcccceessssiinngg SSoouurrccee FFiilleess
/_r_e_g_u_l_a_r _e_x_p_r_e_s_s_i_o_n[/]
?_r_e_g_u_l_a_r _e_x_p_r_e_s_s_i_o_n[?]
Search forward or backward in the current source file
for the given pattern.
eeddiitt [_f_i_l_e_n_a_m_e]
eeddiitt _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n-_n_a_m_e
Invoke an editor on _f_i_l_e_n_a_m_e or the current source
file if none is specified. If a _p_r_o_c_e_d_u_r_e or
_f_u_n_c_t_i_o_n 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 overridden by setting the environment variable
EDITOR to the name of the desired editor.
ffiillee [_f_i_l_e_n_a_m_e] Change the current source file name to _f_i_l_e_n_a_m_e. If
none is specified then the current source file name
is printed.
ffuunncc [_p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n]
Change the current function. If none is specified
then print the current function. Changing the
current function implicitly changes the current
source file to the one that contains the function; it
also changes the current scope used for name
resolution.
lliisstt [_s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r [,,_s_o_u_r_c_e-_l_i_n_e-_n_u_m_b_e_r]
lliisstt _p_r_o_c_e_d_u_r_e/_f_u_n_c_t_i_o_n
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
_n-_k to _n+_k are listed where _n is the first statement
in the procedure or function and _k is small.
uussee _d_i_r_e_c_t_o_r_y-_l_i_s_t
Set the list of directories to be searched when
looking for source files.
CCoommmmaanndd AAlliiaasseess aanndd VVaarriiaabblleess
aalliiaass _n_a_m_e _n_a_m_e
aalliiaass _n_a_m_e _s_t_r_i_n_g
aalliiaass _n_a_m_e (_p_a_r_a_m_e_t_e_r_s) ``_s_t_r_i_n_g''
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''.
sseett _n_a_m_e[_e_x_p_r_e_s_s_i_o_n]
The sseett command defines values for debugger variables. The
names of these variables cannot conflict with names in the pro-
gram being debugged, and are expanded to the corresponding ex-
pression within other commands. The following variables have a
special meaning:
$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 particular use for kernel debugging.
$hexchars
$hexints
$hexoffsets
$hexstrings
When set, dbx prints out out characters, integers,
offsets from registers, or character pointers respective-
ly in hexadecimal.
$listwindow
The value of this variable specifies the number of lines
to list around a function or when the lliisstt 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 debugging.
$unsafecall
$unsafeassign
When ``$unsafecall'' is set, strict type checking is
turned off for arguments to subroutine or function calls
( _e ._g. in the ccaallll statement). When ``$unsafeassign''
is set, strict type checking between the two sides of an
aassssiiggnn statement is turned off. These variables should
be used only with great care, because they severely limit
dbx's usefulness for detecting errors.
uunnaalliiaass _n_a_m_e
Remove the alias with the given name.
uunnsseett _n_a_m_e
Delete the debugger variable associated with _n_a_m_e.
MMaacchhiinnee LLeevveell CCoommmmaannddss
ttrraacceeii [_a_d_d_r_e_s_s] [_c_o_n_d]
ttrraacceeii [_v_a_r_i_a_b_l_e] [aatt_a_d_d_r_e_s_s] [iiff_c_o_n_d]
ssttooppii [_a_d_d_r_e_s_s] [iiff_c_o_n_d]
ssttooppii [aatt] [_a_d_d_r_e_s_s] [iiff_c_o_n_d]
Turn on tracing or set a stop using a machine instruction
address.
sstteeppii
nneexxttii Single step as in sstteepp or nneexxtt, but do a single instruction
rather than source line.
_a_d_d_r_e_s_s,_a_d_d_r_e_s_s/[_m_o_d_e]
_a_d_d_r_e_s_s/[_c_o_u_n_t][_m_o_d_e]
Print the contents of memory starting at the first _a_d_d_r_e_s_s and
continuing up to the second _a_d_d_r_e_s_s or until _c_o_u_n_t items are
printed. If the address is ``.'', the address following the
one printed most recently is used. The _m_o_d_e specifies how
memory is to be printed; if it is omitted the previous mode
specified is used. The initial mode is ``X''. The following
modes are supported:
ii print the machine instruction
dd print a short word in decimal
DD print a long word in decimal
oo print a short word in octal
OO print a long word in octal
xx print a short word in hexadecimal
XX print a long word in hexadecimal
bb print a byte in octal
cc print a byte as a character
ss print a string of characters terminated by a
null byte
ff print a single precision real number
gg print a double precision real number
Symbolic addresses are specified by preceding the name with an
``&''. Registers are denoted by ``$rN'' where N is the number
of the register. Addresses may be expressions made up of other
addresses and the operators ``+'', ``-'', and indirection
(unary ``*'').
MMiisscceellllaanneeoouuss CCoommmmaannddss
ggrriippee Invoke a mail program to send a message to the person in charge
of ddbbxx.
hheellpp Print out a synopsis of ddbbxx commands.
qquuiitt Exit ddbbxx.
sshh _c_o_m_m_a_n_d-_l_i_n_e
Pass the command line to the shell for execution. The SHELL
environment variable determines which shell is used.
ssoouurrccee _f_i_l_e_n_a_m_e
Read ddbbxx commands from the given _f_i_l_e_n_a_m_e.
EENNVVIIRROONNMMEENNTT
DDbbxx utilizes the following environment variables:
EDITOR
HOME
PATH
SHELL
FFIILLEESS
_a._o_u_t object file
._d_b_x_i_n_i_t initial commands
SSEEEE AALLSSOO
cc(1), mod(l), f77(1), pc(1)
HHIISSTTOORRYY
DDbbxx appeared in 4.2 BSD.
BBUUGGSS
DDbbxx suffers from the same ``multiple include'' malady as did ssddbb. 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 de-
bugger start-up is done for each link, having the linker ld(1) 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 ac-
tually the first few bytes of the procedure text; to find the location of
the procedure, use ``&'' to take the address of the variable).