MirOS Manual: c2ph(1), pstruct(1)


C2PH(1)         Perl Programmers Reference Guide          C2PH(1)

NAME

     c2ph, pstruct - Dump C structures as generated from "cc -g
     -S" stabs

SYNOPSIS

         c2ph [-dpnP] [var=val] [files ...]

     OPTIONS

         Options:

         -w  wide; short for: type_width=45 member_width=35 offset_width=8
         -x  hex; short for:  offset_fmt=x offset_width=08 size_fmt=x size_width=04

         -n  do not generate perl code  (default when invoked as pstruct)
         -p  generate perl code         (default when invoked as c2ph)
         -v  generate perl code, with C decls as comments

         -i  do NOT recompute sizes for intrinsic datatypes
         -a  dump information on intrinsics also

         -t  trace execution
         -d  spew reams of debugging output

         -slist  give comma-separated list a structures to dump

DESCRIPTION

     The following is the old c2ph.doc documentation by Tom
     Christiansen <tchrist@perl.com> Date: 25 Jul 91 08:10:21 GMT

     Once upon a time, I wrote a program called pstruct.  It was
     a perl program that tried to parse out C structures and
     display their member offsets for you.  This was especially
     useful for people looking at binary dumps or poking around
     the kernel.

     Pstruct was not a pretty program.  Neither was it particu-
     larly robust. The problem, you see, was that the C compiler
     was much better at parsing C than I could ever hope to be.

     So I got smart:  I decided to be lazy and let the C compiler
     parse the C, which would spit out debugger stabs for me to
     read.  These were much easier to parse.  It's still not a
     pretty program, but at least it's more robust.

     Pstruct takes any .c or .h files, or preferably .s ones,
     since that's the format it is going to massage them into
     anyway, and spits out listings like this:

perl v5.8.8                2006-06-30                           1

C2PH(1)         Perl Programmers Reference Guide          C2PH(1)

      struct tty {
        int                          tty.t_locker                         000      4
        int                          tty.t_mutex_index                    004      4
        struct tty *                 tty.t_tp_virt                        008      4
        struct clist                 tty.t_rawq                           00c     20
          int                        tty.t_rawq.c_cc                      00c      4
          int                        tty.t_rawq.c_cmax                    010      4
          int                        tty.t_rawq.c_cfx                     014      4
          int                        tty.t_rawq.c_clx                     018      4
          struct tty *               tty.t_rawq.c_tp_cpu                  01c      4
          struct tty *               tty.t_rawq.c_tp_iop                  020      4
          unsigned char *            tty.t_rawq.c_buf_cpu                 024      4
          unsigned char *            tty.t_rawq.c_buf_iop                 028      4
        struct clist                 tty.t_canq                           02c     20
          int                        tty.t_canq.c_cc                      02c      4
          int                        tty.t_canq.c_cmax                    030      4
          int                        tty.t_canq.c_cfx                     034      4
          int                        tty.t_canq.c_clx                     038      4
          struct tty *               tty.t_canq.c_tp_cpu                  03c      4
          struct tty *               tty.t_canq.c_tp_iop                  040      4
          unsigned char *            tty.t_canq.c_buf_cpu                 044      4
          unsigned char *            tty.t_canq.c_buf_iop                 048      4
        struct clist                 tty.t_outq                           04c     20
          int                        tty.t_outq.c_cc                      04c      4
          int                        tty.t_outq.c_cmax                    050      4
          int                        tty.t_outq.c_cfx                     054      4
          int                        tty.t_outq.c_clx                     058      4
          struct tty *               tty.t_outq.c_tp_cpu                  05c      4
          struct tty *               tty.t_outq.c_tp_iop                  060      4
          unsigned char *            tty.t_outq.c_buf_cpu                 064      4
          unsigned char *            tty.t_outq.c_buf_iop                 068      4
        (*int)()                     tty.t_oproc_cpu                      06c      4
        (*int)()                     tty.t_oproc_iop                      070      4
        (*int)()                     tty.t_stopproc_cpu                   074      4
        (*int)()                     tty.t_stopproc_iop                   078      4
        struct thread *              tty.t_rsel                           07c      4

     etc.

     Actually, this was generated by a particular set of options.
     You can control the formatting of each column, whether you
     prefer wide or fat, hex or decimal, leading zeroes or what-
     ever.

     All you need to be able to use this is a C compiler than
     generates BSD/GCC-style stabs.  The -g option on native BSD
     compilers and GCC should get this for you.

     To learn more, just type a bogus option, like -\?, and a
     long usage message will be provided.  There are a fair
     number of possibilities.

perl v5.8.8                2006-06-30                           2

C2PH(1)         Perl Programmers Reference Guide          C2PH(1)

     If you're only a C programmer, than this is the end of the
     message for you. You can quit right now, and if you care to,
     save off the source and run it when you feel like it.  Or
     not.

     But if you're a perl programmer, then for you I have some-
     thing much more wondrous than just a structure offset
     printer.

     You see, if you call pstruct by its other incybernation,
     c2ph, you have a code generator that translates C code into
     perl code!  Well, structure and union declarations at least,
     but that's quite a bit.

     Prior to this point, anyone programming in perl who wanted
     to interact with C programs, like the kernel, was forced to
     guess the layouts of the C structures, and then hardwire
     these into his program.  Of course, when you took your
     wonderfully crafted program to a system where the sgtty
     structure was laid out differently, your program broke.
     Which is a shame.

     We've had Larry's h2ph translator, which helped, but that
     only works on cpp symbols, not real C, which was also very
     much needed.  What I offer you is a symbolic way of getting
     at all the C structures.  I've couched them in terms of
     packages and functions.  Consider the following program:

         #!/usr/local/bin/perl

         require 'syscall.ph';
         require 'sys/time.ph';
         require 'sys/resource.ph';

         $ru = "\0" x &rusage'sizeof();

         syscall(&SYS_getrusage, &RUSAGE_SELF, $ru)      && die "getrusage: $!";

         @ru = unpack($t = &rusage'typedef(), $ru);

         $utime =  $ru[ &rusage'ru_utime + &timeval'tv_sec  ]
                + ($ru[ &rusage'ru_utime + &timeval'tv_usec ]) / 1e6;

         $stime =  $ru[ &rusage'ru_stime + &timeval'tv_sec  ]
                + ($ru[ &rusage'ru_stime + &timeval'tv_usec ]) / 1e6;

         printf "you have used %8.3fs+%8.3fu seconds.\n", $utime, $stime;

     As you see, the name of the package is the name of the
     structure.  Regular fields are just their own names.  Plus
     the following accessor functions are provided for your con-
     venience:

perl v5.8.8                2006-06-30                           3

C2PH(1)         Perl Programmers Reference Guide          C2PH(1)

         struct      This takes no arguments, and is merely the number of first-level
                     elements in the structure.  You would use this for indexing
                     into arrays of structures, perhaps like this

                         $usec = $u[ &user'u_utimer
                                     + (&ITIMER_VIRTUAL * &itimerval'struct)
                                     + &itimerval'it_value
                                     + &timeval'tv_usec
                                   ];

         sizeof      Returns the bytes in the structure, or the member if
                     you pass it an argument, such as

                             &rusage'sizeof(&rusage'ru_utime)

         typedef     This is the perl format definition for passing to pack and
                     unpack.  If you ask for the typedef of a nothing, you get
                     the whole structure, otherwise you get that of the member
                     you ask for.  Padding is taken care of, as is the magic to
                     guarantee that a union is unpacked into all its aliases.
                     Bitfields are not quite yet supported however.

         offsetof    This function is the byte offset into the array of that
                     member.  You may wish to use this for indexing directly
                     into the packed structure with vec() if you're too lazy
                     to unpack it.

         typeof      Not to be confused with the typedef accessor function, this
                     one returns the C type of that field.  This would allow
                     you to print out a nice structured pretty print of some
                     structure without knoning anything about it beforehand.
                     No args to this one is a noop.  Someday I'll post such
                     a thing to dump out your u structure for you.

     The way I see this being used is like basically this:

             % h2ph <some_include_file.h  >  /usr/lib/perl/tmp.ph
             % c2ph  some_include_file.h  >> /usr/lib/perl/tmp.ph
             % install

     It's a little tricker with c2ph because you have to get the
     includes right. I can't know this for your system, but it's
     not usually too terribly difficult.

     The code isn't pretty as I mentioned  -- I never thought it
     would be a 1000- line program when I started, or I might not
     have begun. :-)  But I would have been less cavalier in how
     the parts of the program communicated with each other, etc.
     It might also have helped if I didn't have to divine the
     makeup of the stabs on the fly, and then account for micro
     differences between my compiler and gcc.

perl v5.8.8                2006-06-30                           4

C2PH(1)         Perl Programmers Reference Guide          C2PH(1)

     Anyway, here it is.  Should run on perl v4 or greater.
     Maybe less.

      --tom

perl v5.8.8                2006-06-30                           5

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