sdb(1) DG/UX 4.30 sdb(1)
NAME
sdb - symbolic debugger
SYNOPSIS
sdb [-V] [-W] [-w] [objfile [corfile [directory-list]]]
DESCRIPTION
sdb is the symbolic debugger for C and F77 programs. sdb
may be used to examine executable program files and core
files. It may also be used to examine live processes in a
controlled execution environment.
The objfile argument is the name of an executable program
file. To take full advantage of the symbolic capabilities
of sdb, this file should be compiled with the -g (debug)
option. If it has not been compiled with the -g option, the
symbolic capabilities of sdb will be limited, but the file
can still be examined and the program debugged.
The corfile argument is the name of a core image file. A
core image file is produced by the abnormal termination of
objfile. The default for corfile is core. A core image
file need not be present to use sdb. Using a hyphen (-)
instead of corfile forces sdb to ignore an existing core
image file.
The directory-list argument is a colon-separated list of
directories that is used by sdb to locate source files used
to build objfile. If no directory list is specified, sdb
will look in the current directory.
The following options are recognized by sdb:
-V Print version information. If no objfile argument is
specified on the command line, sdb will exit after
printing the version information.
-W Suppress warnings about corfile being older than
objfile or about source files that are older than
objfile.
-w Allow user to write to objfile or corfile.
sdb recognizes a current line and a current file. When sdb
is examining an executable program file without a core file,
the current line and current file are initially set to the
line and file containing the first line of main. If corfile
exists, then current line and current file are initially set
to the line and file containing the source statement where
the process terminated. Note that on the 88K, this may not
be the instruction which actually caused the process to
terminate. The current line and current file change
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automatically as a live process executes. They may also be
changed with the source file examination commands.
Names of variables are written as in C. 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.
Structure members may be referred to as variable.member,
pointers to structure members as variable->member, and array
elements as variable[number]. Pointers may also be
dereferenced by using the form pointer[number].
Combinations of these forms may also be used. The form
number->member may be used where number is the address of a
pointer, and number.member where number is interpreted as
the address of a structure instance. The template of the
structure type used in this case will be the last structure
type referenced. When sdb displays the value of a
structure, it does so by displaying the value of all
elements of the structure. The address of a structure is
displayed by displaying the address of the structure
instance rather than the addresses of individual elements.
Elements of a multidimensional array may be referred to as
variable [number][number]..., or as variable
[number,number,...]. In place of number, the form
number;number may be used to indicate a range of values, *
may be used to indicate all legitimate values for that
subscript, or subscripts may be omitted entirely if they are
the last subscripts and the full range of values is desired.
If no subscripts are specified, sdb will display the value
of all elements of the array.
A particular instance of a variable on the stack is referred
to as procedure:variable,number. The number is the
occurrence of the specified procedure on the stack, with the
topmost occurrence being 1. The default procedure is the
one containing the current line.
Addresses may be used in sdb commands as well. Addresses
are specified by decimal, octal, or hexadecimal numbers.
Line numbers in the source program are specified by the form
filename:number or procedure:number. In either case, the
number is relative to the beginning of the file and
corresponds to the line number used by text editors or the
output of pr. A number used by itself implies a line in the
current file.
While a live process is running under sdb, all addresses and
identifiers refer to the live process. When sdb is not
examining a live process, the addresses and identifiers
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refer to objfile or corfile.
Commands
The commands for examining data in the program are:
t Prints a stack trace of the terminated or halted
program. The function invoked most recently is at the
top of the stack.
T Prints the top line of the stack trace.
variable/clm
Prints the value of variable according to length l and
format m. The numeric count c indicates that a region
of memory, beginning at the address implied by
variable, is to be displayed. 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 signed decimal
u unsigned decimal
o octal
x hexadecimal
X hexadecimal (uppercase)
f 32-bit single precision floating point
g 64-bit double precision floating point
s Assumes that 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. Do not use this with register variables.
p pointer to procedure
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i Disassembles machine-language instruction with
addresses printed numerically and symbolically.
I Disassembles machine-language instruction with
addresses printed numerically only.
Length specifiers are effective with formats c, d, u,
o, x. The length specifier determines the output
length of the value to be displayed. This value may be
truncated. The count specifier c displays that many
units of memory, starting at the address of the
variable. The number of bytes in the unit of memory is
determined by l or by the size associated with the
variable. If the specifiers c, l, and m are omitted,
sdb uses defaults. If a count specifier is used with
the s or a command, then that many characters are
printed. Otherwise, successive characters are printed
until either a null byte is reached or 128 characters
are printed. The last variable may be redisplayed with
the ./ command.
For a limited form of pattern matching, use the sh
metacharacters * and ? within procedure and variable
names. (sdb does not accept these metacharacters in
file names, as the function name in a line number when
setting a breakpoint, in the function call command, or
as the argument to the e command.) If no procedure
name is supplied, sdb matches both local and global
variables. If the procedure name is specified, then
sdb matches only local variables. To match global
variables only, use :pattern. To print all variables,
use *:*.
linenumber?lm
variable:?lm
Prints the value at the address from the executable or
text space given by linenumber or variable (procedure
name), according to the format lm. The default format
is i.
variable=lm
linenumber=lm
number=lm
Prints the address of variable or linenumber, or the
value of number. l specifies length and m specifies the
format. If no format is specified, then sdb uses lx
(four-byte hex). m allows you to convert between
decimal, octal, and hexadecimal.
variable!value
Sets variable to the given value. The value may be a
number, a character constant, or a variable. The value
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must be well-defined. Character constants are denoted
'character. Numbers are viewed as integers unless a
decimal point or exponent is used. In this case, they
are treated as having the type double. Registers,
except the floating point registers, are viewed as
integers. Register names are identical to those used by
the assembler, but with an appended %. (for example,
regname% where regname is the name of a register). R30
and r31 are accessed with fp% and sp%. If the address
of a variable is given, it is regarded as the address
of a variable of type int. C conventions are used in
any type conversions necessary to perform the indicated
assignment. If sdb is invoked with the -w flag,
writing to text addresses before the execution of the
program, (objfile), will change the actual values in
the objfile, not just the image in memory. This is not
true once execution has begun.
x Prints the machine registers and the current machine-
language instruction.
X Prints the current machine-language instruction.
The commands for examining source files are:
e
e procedure
e filename
e directory/
e, without arguments, prints the name of the current
file. The second form sets the current file to the
file containing the procedure. The third form sets the
current file to filename. The current line is set to
the first line in the named procedure or file. Source
files are assumed to be in the directories in the
directory list. The fourth form adds directory to the
end of the directory list, replacing any directory
previously added with the e command.
/regular expression/
Searches forward from the current line for a line
containing a string matching regular expression, as in
ed. The trailing / may be omitted, except when
associated with a breakpoint.
?regular expression?
Searches backward from the current line for a line
containing a string matching regular expression, as in
ed. The trailing ? may be omitted, except when
associated with a breakpoint.
p Prints the current line.
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z Prints the current line and the following nine lines.
Sets the current line to the last line printed.
w Prints the 10 lines (the window) around the current
line.
number
Specifies the current line. Prints the new current
line.
count+
Advances the current line by count lines. Prints the
new current line.
count-
Resets the current line by count lines back. Prints
the new current line.
The commands for controlling the execution of the source
program are:
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. The R command runs the program with no
arguments. An argument beginning with < or > redirects
the standard input or output, respectively. Full sh
syntax is accepted. If count is given, it specifies
the number of breakpoints to be ignored.
linenumber c count
linenumber C count
Continues execution. sdb stops when it encounters
count breakpoints. The signal that stopped the program
is reactivated with the C command and ignored with the
c command. If a line number is specified, then a
temporary breakpoint is placed at the line and
execution continues. The breakpoint is deleted when
the command finishes.
linenumber g count
Continues with execution resumed at the given line. If
count is given, it specifies the number of breakpoints
to be ignored. Results are undefined if linenumber is
in a different context (eg. another procedure).
s count
S count
s single steps the program through count lines or if no
count is given, then the program runs for one line. s
will step from one function into a called function. S
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also steps a program, but it will not step into a
called function. It steps over the function called.
i count
I count
Single steps by count machine-language instructions.
The signal that caused the program to stop is
reactivated with the I command and ignored with the i
command.
variable$m count
address:m count
Single steps (as with s) until the specified location
is modified with a new value. If count is omitted, it
is, in effect, infinity. Variable must be accessible
from the current procedure. This command can be very
slow.
level v
Toggles verbose mode. This is for use when single
stepping with S, s, or m. If level is omitted, then
just the current source file and/or function name is
printed when either changes. If level is 1 or greater,
each C source line is printed before it executes. If
level is 2 or greater, each assembler statement is also
printed. A v turns verbose mode off.
k Kills the program being debugged.
procedure(arg1,arg2,...)
procedure(arg1,arg2,...)/m
Executes the named procedure with the given arguments.
Arguments can be register names, integer, character, or
string constants, or names of variables accessible from
the current procedure. The second form causes the
value returned by the procedure to be printed according
to format m. If no 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., proc:), a
breakpoint is placed at the first line in the procedure
even if it was not compiled with the -g option. If no
linenumber is given, a breakpoint is placed at the
current line. If no commands are given, execution
stops at the breakpoint and control is returned to sdb.
Otherwise the commands are executed when the breakpoint
is encountered. Multiple commands are specified by
separating them with semicolons. Nested associated
commands are not permitted; setting breakpoints within
the associated environments is permitted.
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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.
linenumber a
Announces a line number. If linenumber is of the form
proc:number, the command effectively does a
linenumber:b l;c. If linenumber is of the form proc:,
the command effectively does a proc:b T;c.
Miscellaneous commands:
!command
The command is interpreted by sh.
new-line
If the previous command printed a source line, then
advance the current line by one line and print the new
current line. If the previous command displayed a
memory location, then display the next memory location.
If the previous command disassembled an instruction,
then disassemble the next instruction.
end-of-file character
Scrolls the next 10 lines of instructions, source, or
data depending on which was printed last. The end-of-
file character is usually control-d.
< filename
Read commands from filename until the end of file is
reached, and then continue to accept commands from
standard input. Commands are echoed, preceded by two
asterisks, just before being executed. This command
may not be nested; < may not appear as a command in a
file.
M Prints the address maps.
" string "
Prints the given string. The C escape sequences of the
form \character, \octaldigits, or \xhexdigits are
recognized, where character is a nonnumeric character.
The trailing quote may be omitted.
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q Exits the debugger.
V Prints version stamping information.
SEE ALSO
cc(1), signal(2), a.out(4), core(4), syms(4).
ed(1), sh(1) in the User's Reference Manual.
The ``sdb'' chapter in the Programmer's Guide: ANSI C and
Programming Support Tools.
WARNINGS
When sdb prints the value of an external variable for which
there is no debugging information, a warning is printed
before the value. The size is assumed to be int (integer).
Data which are stored in text sections are indistinguishable
from functions.
Line number information in optimized functions is
unreliable, and some information may be missing.
Function calls from within sdb cannot be made before main is
reached. Arguments in function calls are limited in size to
32 bits (pointers are allowed).
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