SDB(1)

NAME
sdb - symbolic debugger

SYNOPSIS
sdb [ objfil [ corfil [ directory ] ] ]

DESCRIPTION
Sdb is a symbolic debugger which can be used with C and F77 programs. It may be used to examine their files and to provide a controlled environment for their execution.

Objfil is an executable program file which has been compiled with the -g (debug) 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. The core file need not be present.

It is useful to know that at any time there is a current line and current file. If corfil exists then they are initially set to the line and file containing the source statement at which the process terminated or stopped. Otherwise, they are 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 or F77. 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. It is also possible to refer to structure members as `variable.member', pointers to structure members as `variable->member' and array elements as `variable[number]'. Combinations of these forms may also be used.

It is also possible to specify a variable by its address. All forms of integer constants which are valid in C may be used, so that addresses may be input in decimal, octal or hexadecimal.

Line numbers in the source program 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 file name 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.

The commands for examining data in the program are:

t   Print a stack trace of the terminated or stopped program.

T   Print the top line of the stack trace.

variable/lm
    Print the value of variable according to length l and format m. If l and m are omitted, sdb chooses a length and format suitable for the variable's type as declared in the program. The length specifiers are:

    b   one byte

    h   two bytes (half word)

    l   four bytes (long word)

    number
        string length for formats s and a

    Legal values for m are:

    c   character

    d   decimal

    u   decimal, unsigned

    o   octal

    x   hexadecimal

    f   32 bit single precision floating point

    g   64 bit double precision floating point

    s   Assume variable is a string pointer and print characters until a null is reached.

    a   Print characters starting at the variable's address until a null is reached.

    p   pointer to procedure

    The length specifiers are only effective with the formats d, u, o and x. If one of these formats is specified and l is omitted, the length defaults to the word length of the host machine; 4 for the DEC VAX/11-780. The last variable may be redisplayed with the command `./'.

    The sh(1) metacharacters * and ? may be used within procedure and variable names, providing a limited form of pattern matching. If no procedure name is given, both variables local to the current procedure and global (common for F77) variables are matched, while if a procedure name is specified then only variables local to that procedure and matched. To match only global variables (or blank common for F77), the form `:pattern' is used. The name of a common block may be specified instead of a procedure name for F77 programs.

variable=lm

linenumber=lm

number=lm
    Print the address of the variable or line number or the value of the number in the specified format. 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.

variable!value
    Set the variable to the given value. The value may be a number, character constant or a variable. If the variable is of type float or double, the value may also be a floating constant.

The commands for examining source files are

e procedure

e filename.c
    Set the current file to the file containing the named procedure or the named filename. Set the current line to the first line in the named procedure or file. All source files are assumed to be in directory. The default for directory is the working directory. If no procedure or file name is given, the current procedure and file names are reported.

/regular expression/
    Search forward from the current line for a line containing a string matching the regular expression as in ed(1). The trailing `/' may be elided.

?regular expression?
    Search backward from the current line for a line containing a string matching the regular expression as in ed(1). The trailing `?' may be elided.

p   Print the current line.

z   Print the current line followed by the next 9 lines. Set the current line to the last line printed.

control-D
    Scroll. Print the next 10 lines. Set the current line to the last line printed.

w   Window. Print the 10 lines around the current line.

number
    Set the current line to the given line number. Print the new current line.

count +
    Advance the current line by count lines. Print the new current line.

count -
    Retreat the current line by count lines. Print the new current line.

The commands for controlling the execution of the source program are:

count r args

count R
    Run 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
    Continue 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 and c ignores it.

    If a linenumber is specified then a temporary breakpoint is placed at the line and execution is continued. The breakpoint is deleted when the command finishes.

count s
    Single step. Run the program through count lines. If no count is given then the program is run for one line.

count S
    Single step, but step through subroutine calls.

k   Kill the debugged program.

procedure(arg1,arg2,...)

procedure(arg1,arg2,...)/m
    Execute the named procedure with the given arguments. Arguments can be 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
    Set 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 debug flag. 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.

linenumber d
    Delete 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.

B   Print a list of the currently active breakpoints.

D   Delete all breakpoints.

l   Print the last executed line.

linenumber a
    Announce. If linenumber is of the form `proc: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
    The command is interpreted by sh(1).

newline
    If the previous command printed a source line then advance the current line by 1 line and print the new current line. If the previous command displayed a core location then display the next core location.

" string
    Print the given string.

q   Exit the debugger.

The following commands also exist and are intended only for debugging the debugger.

V   Print the version number.

X   Print a list of procedures and files being debugged.

Y   Toggle debug output.

FILES
a.out
core

SEE ALSO
adb(1)

DIAGNOSTICS
Error reports are either identical to those of adb(1) or are self-explanatory.

BUGS
If a procedure is called when the program is not stopped at a breakpoint (such as when a core image is being debugged), all variables are initialized before the procedure is started. This makes it impossible to use a procedure which formats data from a core image.

Arrays must be of one dimension and of zero origin to be correctly addressed by sdb.

The default type for printing F77 parameters is incorrect. Their address is printed instead of their value.

Tracebacks containing F77 subprograms with multiple entry points may print too many arguments in the wrong order, but their values are correct.