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Linux 2.6 - man page for c2ph (linux section 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 particularly 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:

	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 whatever.

       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.

       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 something 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 convenience:

	   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.

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

	--tom


perl v5.12.4				    2013-03-18					  C2PH(1)


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