SDB(CP) XENIX System V SDB(CP)
Name
sdb - Invokes symbolic debugger.
Syntax
sdb [ objfil [ corfil [ directory:directory ]]]
Description
sdb is a symbolic debugger which can be used with C
programs.
Objfil is an executable program file which has been compiled
with the -Zi (debug) option and linked with the -I option.
The default for objfil is a.out. Corfil is assumed to be a
core image file produced after executing objfil; the default
for corfil is core. A ``-'' in place of corfil forces sdb
to ignore any core image file. The colon separated
directory list is used to locate the source files used to
build objfil.
It is useful to know that at any time there is a current
line and current file. They are initially set to the first
line in main(). The current line and file may be changed
with the source file examination commands.
Names of variables are written just as they are in C
programs. Variables local to a procedure may be accessed
using the form procedure.variable. If no procedure name is
given, the procedure containing the current line is used by
default.
You can also refer to structure members as variable.member,
pointers to structure members as variable->member and array
elements as variable[number]. Pointers may be de-referenced
by using the form pointer[0]. You can also use combinations
of these forms.
It is also possible to specify a variable by its address.
You can use all forms of integer constants which are valid
in C programs, so that addresses and numbers may be input in
decimal, octal, or hexadecimal.
Line numbers in source programs are referred to as
filename:number or procedure:number. In either case the
number is relative to the beginning of the file. If no
procedure or filename is given, the current file is used by
default. If no number is given, the first line of the named
procedure or file is used.
There are several kinds of commands available to the sdb
debugger as described in the following sections. sdb
commands appear in boldface type. For all commands, items in
brackets ([ ]) are optional.
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Data Examination Commands
t Displays a stack trace.
T Prints the top line of the stack trace.
variable/[clm]
Displays the value of variable according to length l and
format m. A numeric count c indicates that a region of
memory, beginning at the address implied by variable, is to
be displayed. If l and m are omitted, sdb chooses a format
suitable for the variable type as declared in the program.
The length specifiers are:
b One byte
h Two bytes (half word)
l Four bytes (long word)
Legal values for
m are:
c Character
d Decimal
u Unsigned decimal
o Octal
x Hexadecimal
f 32 bit single precision floating point
g 64 bit single precision floating point
s Assumes variable is a string pointer and
prints characters starting at the address
pointed to by the variable.
a Prints characters starting at the variable's
address.
i Disassembles with numeric/symbolic addresses.
The length specifiers are only effective with the
formats c, d, u, o, and x. If one of these formats is
specified and l is omitted, the length defaults to two
bytes. If a numeric length specifier is used for the
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format variable then that many characters are printed.
Otherwise, successive characters are printed until
either a null byte is reached or 128 characters are
printed.
linenumber?[clm]
Prints the value at the address from a.out or i space given
by linenumber, according to the format lm. The default
format is i.
variable=[lm]
linenumber=[lm]
number=[lm]
Prints the address of variable or linenumber in the format
specified by lm . If no format is given, then lx is used.
The last variant of this command provides a convenient way
to convert between decimal, octal, and hexadecimal. A
single number cannot be used as a line number because the
command would be ambiguous; the proc:number form must be
used.
variable!value
Sets variable to the given value. The value may be any
valid C expression.
x Displays the machine registers and current machine-
language instruction.
X Displays the current machine-language instruction.
Source File Examination Commands
e Displays current procedure and filenames.
e procedure
Sets the current file and current line to the file
containing procedure.
e filename
Sets the current file and current line number to the first
line in filename .
/regular expression[/]
Searches forward from the current line for a line containing
a string matching regular expression as in ed(C).
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?regular expression[?]
Searches backward from the current line for a line
containing a string matching regular expression as in ed(C).
p Prints the current line.
z Prints the current line followed by the next nine
lines. Sets the current line to the last line printed.
w Creates a window by printing ten lines around the
current line.
number
Sets the current line to the given line number and displays
the line.
[count]+
Advances the current line by count lines and display the new
line. If count is omitted, the default is one line.
[count]-
Retreats from the current line by count lines and display
the new line. If count is omitted, the default is one line.
Execution Control Commands
L Load the program to be debugged but do not run it. If
you wish to examine the initial values of memory
locations before the program has started to run, or if
you wish to disassemble portions of the program without
actually running it, you must first enter the L
command.
[count] r [args]
[count] R
Runs the program with the given arguments. The r
command with no arguments reuses the previous arguments
to the program while the R command runs the program
with no arguments. An argument beginning with < or >
causes redirection for the standard input or output
respectively. If count is given, it specifies the
number of breakpoints to be ignored.
[linenumber] c [count]
[linenumber] C [count]
Continues after a breakpoint or interrupt. If count is
given, it specifies the number of breakpoints to be
ignored. C continues with the signal which caused the
program to stop reactivated and c ignores it. If a
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line number is specified then a temporary breakpoint is
placed at the line and execution is continued. The
breakpoint is deleted when the command finishes.
linenumber g [count]
Continues after a breakpoint with execution resumed at
the given line. If count is given, it specifies the
number of breakpoints to be ignored.
[count] s
Single steps. Runs the program through count lines.
If no count is given then the program is run for one
line.
[count] S
Single steps but steps through subroutine calls.
[count] i
Machine-language single steps. Runs the program
through count machine-language instructions. If no
count is given then one machine-language instruction is
executed.
[count] I
Machine-language single steps, but steps through call
instructions.
variable$m [count]
Single steps (as with s) until the specified location
is modified with a new value. Count specifies the
number of instructions to step; if omitted, count is
effectively infinity. The variable must be accessible
from the current procedure. Since this command is
performed by software, it can be very slow.
[level] v
Switches verbose mode on and off, for use with single
stepping with S, s, or m. If level is omitted or is
zero, then just the current source file and/or
subroutine name is printed when either changes. If
level is one, each C source line is printed before it
is executed; if level is two, each assembler line
statement is also printed. The v command turns verbose
mode off if it is on for any level.
k Kills the debugged program.
procedure(arg1,arg2,...)
procedure(arg1,arg2,...)/m
Executes the named procedure with the given arguments.
The second form causes the value to be returned by the
procedure to be printed according to format m. If no
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format is given, it defaults to d.
[linenumber] b [commands]
Sets a breakpoint at the given line. If a procedure
name without a line number is given (e.g., a breakpoint
is placed at the first line in the procedure. If no
linenumber is given, a breakpoint is placed at the
current line. If no commands are given then execution
stops just before the breakpoint and control is
returned to sdb. Otherwise the commands are executed
when the breakpoint is encountered and execution
continues. Multiple commands are specified by
separating them with semicolons.
B Prints a list of the currently active breakpoints.
[linenumber] d
Deletes a breakpoint at the given line. If no
linenumber is given, then the breakpoints are deleted
interactively: each breakpoint location is printed and
a line is read from the standard input. If the line
begins with a y or d, then the breakpoint is deleted.
D Deletes all breakpoints.
l Prints the last executed line. Makes the last executed
line the current line.
linenumber a
Announces. If linenumber is of the form proc:number or
number, the command effectively does a linenumber b l.
If linenumber is of the form proc:, the command
effectively does a proc: b T.
Miscellaneous Commands
!command
Interprets command. Command interpreter executes
command.
newline
Advances the current line by one line and prints the
new current line if the previous command printed a
source line. Displays the next memory location if the
previous command displayed a memory location.
Ctrl-D
Scrolls. Prints the next ten lines of instructions,
source or data depending on which was printed last.
< filename
Reads commands from filename until the end of file is
reached, and then continues to accept commands from
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standard input. When sdb is told to display a variable
by a command in such a file, the variable name is
displayed along with the value. This command may not
be nested; the redirection character (<) may not appear
as a command in a file.
"string
Prints the given string. The C escape sequences of the
form \character are recognized, where character is a
non-numeric character.
q Exits the debugger.
Debugger Commands
V Prints the version number.
Q Prints a list of procedures and files being debugged.
Files
a.out
core
See Also
adb(CP), a.out(F), cc(CP), core(F), ld(CP)
Notes
In order to make use of the symbolic debugging features of
sdb, the program being debugged must have been compiled with
the -Zi option. sdb does not use the ordinary symbol table
information in an a.out file and has limited facilities for
debugging at the machine code level. If you have to debug a
program that has been compiled without using the -Zi option,
it may be preferable to use adb.
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