ACID(1)                                                   ACID(1)

     NAME
          acid, acidtypes - debugger

     SYNOPSIS
          acid [ -l library ] [ -wq ] [ -m machine ] [ pid | core ] [
          textfile ]

          acidtypes [ -p prefix ] file ...

     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 (a.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       Print variable renamings at startup.

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

          -m machine
                   Assume instructions are for the given CPU type (see
                   mach(3)) instead of using the executable header to
                   select the CPU type.

          -k       Debug the kernel state for the process, rather than
                   the user state.

          At startup, acid obtains standard function definitions from
          the library file /acid/port, architecture-dependent func-
          tions from /acid/$objtype, user-specified functions from
          $home/lib/acid, and further functions from -l files.  Defi-
          nitions in any file may override previously defined func-
          tions.  If the function acidinit() is defined, it will be
          invoked after all modules have been loaded.  Then the func-
          tion acidmap() will be invoked if defined.  /acid/port pro-
          vides a definition of acidmap that attaches all the shared
          libraries being used by the target process and then runs
          acidtypes (q.v.)  to create 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

     ACID(1)                                                   ACID(1)

          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
          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(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 }
               defn name
               name(args)
               builtin name(args)
               local name
               return expr
               whatis [  name ]

          The statement defn name clears the definition for name. A
          defn may override a built-in function; prefixing a function
          call with builtin ignores any overriding defn, forcing the
          use of the built-in function.

          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

     ACID(1)                                                   ACID(1)

                        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 sam(1) and select
                        it.
          line(address) Print source line nearest to the program
                        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.  (Doesn't work on Unix yet.)
          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.  (Doesn't work on Unix yet.)
          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

     ACID(1)                                                   ACID(1)

                        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, rc(1), to execute the
                        command string.
          include(string)
                        Read acid commands from the named file.
          includepipe(string)
                        Run the command string, reading its standard
                        output as acid commands.

        Shared library segments
          When a pid or core file is specified on the command line,
          acid will, as part of its startup, determine the set of
          shared libraries in use by the process image and map those
          at appropriate locations.  If acid is started without a pid
          or core file and is subsequently attached to a process via
          setproc, the shared library maps can be initialized by call-
          ing dynamicmap().

        Type information
          Unix compilers conventionally include detailed type informa-
          tion in the debugging symbol section of binaries.  The
          external program acidtypes extracts this information and
          formats it as acid program text.  Once the shared libraries
          have been mapped, the default acid startup invokes acidtypes
          (via includepipe) on the set of currently mapped text files.
          The function acidtypes() can be called to rerun the command
          after changing the set of mapped text files.

        Acid Libraries
          There are a number of acid `libraries' that provide higher-
          level debugging facilities.  One notable example is trump,
          which uses acid to trace memory allocation.  Trump requires
          starting acid on the program, either by attaching to a run-
          ning process or by executing new() on a binary (perhaps
          after setting progargs), stopping the process, and then run-
          ning trump() to execute the program under the scaffolding.
          The output will be a trace of the memory allocation and free
          calls executed by the program.  When finished tracing, stop
          the process and execute untrump() followed by cont() to
          resume execution.

     EXAMPLES
          Start to debug /bin/ls; set some breakpoints; run up to the
          first one (this example doesn't work on Unix yet):

     ACID(1)                                                   ACID(1)

               % acid /bin/ls
               /bin/ls: mips plan 9 executable
               /sys/lib/acid/port
               /sys/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; };
               s = *headstr;
               while s != 0 do{
                    complex Str s;
                    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.

          Trace the system calls executed by ls(1) (neither does this
          one):

               % acid -l truss /bin/ls
               /bin/ls:386 plan 9 executable

               /sys/lib/acid/port
               /sys/lib/acid/kernel
               /sys/lib/acid/truss
               /sys/lib/acid/386
               acid: progargs = "-l lib/profile"
               acid: new()
               acid: truss()
               open("#c/pid", 0)

     ACID(1)                                                   ACID(1)

                    return value: 3
               pread(3, 0x7fffeeac, 20, -1)
                    return value: 12
                    data: "        166 "
               ...
               stat("lib/profile", 0x0000f8cc, 113)
                    return value: 65
               open("/env/timezone", 0)
                    return value: 3
               pread(3, 0x7fffd7c4, 1680, -1)
                    return value: 1518
                    data: "EST -18000 EDT -14400
                  9943200   25664400   41392800   57718800   73447200   89168400
                104896800  ..."
               close(3)
                    return value: 0
               pwrite(1, "--rw-rw-r-- M 9 rob rob 2519 Mar 22 10:29 lib/profile
               ", 54, -1)
               --rw-rw-r-- M 9 rob rob 2519 Mar 22 10:29 lib/profile
                    return value: 54
               ...
               166: breakpoint     _exits+0x5     INTB $0x40
               acid: cont()

     FILES
          /acid/$objtype
          /acid/port
          /acid/kernel
          /acid/trump
          /acid/truss
          $home/lib/acid

     SOURCE
          /src/cmd/acid

     SEE ALSO
          mk(1), db(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

     ACID(1)                                                   ACID(1)

          debug across process forks.

          Breakpoints do not work yet.  Therefore, commands such as
          step, new, and truss do not work either.  New in particular
          will need some help to cope with dynamic libraries.