ACID(10.1)                                             ACID(10.1)

     NAME
          acid - debugger

     SYNOPSIS
          acid [ -l libfile ] [ -wq ] [ -m machine ] [ pid ] [
          textfile ]

     DESCRIPTION
          Acid is a programmable symbolic debugger.  It can inspect
          one or more processes that share an address space.  A pro-
          gram to be debugged may be specified by the process id of a
          running or defunct process, or by the name of the program's
          text file (v.out by default).  At the prompt, acid will
          store function definitions or print the value of expres-
          sions.  Options are

          -w       Allow the textfile to be modified.

          -q       Don't print variable renamings at startup.

          -l library
                   Load from library at startup; see below.

          -m machine
                   Assume instructions are for the given CPU type (one
                   of 386, 86, 68020, 960, power, arm, mips, mipsco,
                   sparc, or sunsparc) instead of using the magic num-
                   ber to select the CPU type.

          At startup, acid obtains standard function definitions from
          the library file /lib/acid/port, architecture-dependent
          functions from /lib/acid/$objtype, user-specified functions
          from $home/lib/acid, and further functions from -l files.
          Definitions in any file may override previously defined
          functions.  If the function acidinit() is defined, it will
          be invoked after all modules have been loaded.  See 2c(10.1)
          for information about creating acid functions for examining
          data structures.

        Language
          Symbols of the program being debugged become integer vari-
          ables whose values are addresses.  Contents of addresses are
          obtained by indirection.  Local variables are qualified by
          function name, for example main:argv.  When program symbols
          conflict with acid words, distinguishing $ signs are pre-
          fixed.  Such renamings are reported at startup; option -q
          suppresses them.

          Variable types (integer, float, list, string) and formats
          are inferred from assignments.  Truth values false/true are

     ACID(10.1)                                             ACID(10.1)

          attributed to zero/nonzero integers or floats and to
          empty/nonempty lists or strings.  Lists are sequences of
          expressions surrounded by {} and separated by commas.

          Expressions are much as in C, but yield both a value and a
          format.  Casts to complex types are allowed.  Lists admit
          the following operators, with subscripts counted from 0.

               head list
               tail list
               append list, element
               delete list, subscript

          Format codes are the same as in db(10.1). Formats may be
          attached to (unary) expressions with \, e.g.  (32*7)\D.
          There are two indirection operators, * to address a core
          image, @ to address a text file.  The type and format of the
          result are determined by the format of the operand, whose
          type must be integer.

          Statements are

               if expr then statement [ else statement ]
               while expr do statement
               loop expr, expr do statement
               defn name(args) { statement }
               local name
               return expr
               whatis [  name ]

          Here is a partial list of functions; see the manual for a
          complete list.

          stk()         Print a stack trace for current process.
          lstk()        Print a stack trace with values of local vari-
                        ables.
          gpr()         Print general registers.  Registers can also
                        be accessed by name, for example *R0.
          spr()         Print special registers such as program
                        counter and stack pointer.
          fpr()         Print floating-point registers.
          regs()        Same as spr();gpr().
          fmt(expr,format)
                        Expression expr with format given by the char-
                        acter value of expression format.
          src(address)  Print 10 lines of source around the program
                        address.
          Bsrc(address) Get the source line for the program address
                        into a window of a running editor and select
                        it.  (This works only on Plan 9, or a Unix-
                        like system running `Plan 9 Ports'.)
          line(address) Print source line nearest to the program

     ACID(10.1)                                             ACID(10.1)

                        address.
          source()      List current source directories.
          addsrcdir(string)
                        Add a source directory to the list.
          filepc(where) Convert a string of the form
                        sourcefile:linenumber to a machine address.
          pcfile(address)
                        Convert a machine address to a source file
                        name.
          pcline(address)
                        Convert a machine address to a source line
                        number.
          bptab()       List breakpoints set in the current process.
          bpset(address)
                        Set a breakpoint in the current process at the
                        given address.
          bpdel(address)
                        Delete a breakpoint from the current process.
          cont()        Continue execution of current process and wait
                        for it to stop.
          step()        Execute a single machine instruction in the
                        current process.
          func()        Step repeatedly until after a function return.
          stopped(pid)  This replaceable function is called automati-
                        cally when the given process stops.  It nor-
                        mally prints the program counter and returns
                        to the prompt.
          asm(address)  Disassemble 30 machine instructions beginning
                        at the given address.
          mem(address,string)
                        Print a block of memory interpreted according
                        to a string of format codes.
          dump(address,n,string)
                        Like mem(), repeated for n consecutive blocks.
          print(expr,...)
                        Print the values of the expressions.
          newproc(arguments)
                        Start a new process with arguments given as a
                        string and halt at the first instruction.
          new()         Like newproc(), but take arguments (except
                        argv[0]) from string variable progargs.
          win()         Like new(), but run the process in a separate
                        window.
          start(pid)    Start a stopped process.
          kill(pid)     Kill the given process.
          setproc(pid)  Make the given process current.
          rc(string)    Escape to the shell, to execute the command
                        string.

     EXAMPLES
          Start to debug /bin/ls; set some breakpoints; run up to the
          first one:

     ACID(10.1)                                             ACID(10.1)

               % acid /bin/ls
               /bin/ls: mips plan 9 executable
               /lib/acid/port
               /lib/acid/mips
               acid: new()
               70094: system call  _main       ADD     $-0x14,R29
               70094: breakpoint   main+0x4    MOVW    R31,0x0(R29)
               acid: pid
               70094
               acid: argv0 = **main:argv\s
               acid: whatis argv0
               integer variable format s
               acid: *argv0
               /bin/ls
               acid: bpset(ls)
               acid: cont()
               70094: breakpoint  ls   ADD $-0x16c8,R29
               acid:

          Display elements of a linked list of structures:

               complex Str { 'D' 0 val; 'X' 4 next; };
               complex Str s;
               s = *headstr;
               while s != 0 do{
                    print(s.val, "\n");
                    s = s.next;
               }

          Note the use of the . operator instead of ->.

          Display an array of bytes declared in C as char array[].

               *(array\s)

          This example gives array string format, then prints the
          string beginning at the address (in acid notation) *array.

     FILES
          /proc/*/text
          /proc/*/mem
          /proc/*/ctl
          /proc/*/note
          /lib/acid/$objtype
          /lib/acid/port
          $home/lib/acid

     SOURCE
          /utils/acid

     SEE ALSO
          2a(10.1), 2c(10.1), 2l(10.1), mk(10.1), db(10.1)

     ACID(10.1)                                             ACID(10.1)

          Phil Winterbottom, ``Acid Manual''.

     DIAGNOSTICS
          At termination, kill commands are proposed for processes
          that are still active.

     BUGS
          There is no way to redirect the standard input and standard
          output of a new process.
          Source line selection near the beginning of a file may pick
          an adjacent file.
          With the extant stepping commands, one cannot step through
          instructions outside the text segment and it is hard to
          debug across process forks.