1C2PH(1) Perl Programmers Reference Guide C2PH(1)
2
6 c2ph, pstruct - Dump C structures as generated from "cc -g -S" stabs
7
9 c2ph [-dpnP] [var=val] [files ...]
10 OPTIONS
12 Options:
14 -w wide; short for: type_width=45 member_width=35 offset_width=8
16 -x hex; short for: offset_fmt=x offset_width=08 size_fmt=x size_width=04
17 -n do not generate perl code (default when invoked as pstruct)
19 -p generate perl code (default when invoked as c2ph)
20 -v generate perl code, with C decls as comments
21 -i do NOT recompute sizes for intrinsic datatypes
23 -a dump information on intrinsics also
24 -t trace execution
26 -d spew reams of debugging output
27 -slist give comma-separated list a structures to dump
29
31 The following is the old c2ph.doc documentation by Tom Christiansen
32 <tchrist@perl.com> Date: 25 Jul 91 08:10:21 GMT
33 Once upon a time, I wrote a program called pstruct. It was a perl pro‐
35 gram that tried to parse out C structures and display their member off‐
36 sets for you. This was especially useful for people looking at binary
37 dumps or poking around the kernel.
38 Pstruct was not a pretty program. Neither was it particularly robust.
40 The problem, you see, was that the C compiler was much better at pars‐
41 ing C than I could ever hope to be.
42 So I got smart: I decided to be lazy and let the C compiler parse the
44 C, which would spit out debugger stabs for me to read. These were much
45 easier to parse. It's still not a pretty program, but at least it's
46 more robust.
47 Pstruct takes any .c or .h files, or preferably .s ones, since that's
49 the format it is going to massage them into anyway, and spits out list‐
50 ings like this:
51 struct tty {
53 int tty.t_locker 000 4
54 int tty.t_mutex_index 004 4
55 struct tty * tty.t_tp_virt 008 4
56 struct clist tty.t_rawq 00c 20
57 int tty.t_rawq.c_cc 00c 4
58 int tty.t_rawq.c_cmax 010 4
59 int tty.t_rawq.c_cfx 014 4
60 int tty.t_rawq.c_clx 018 4
61 struct tty * tty.t_rawq.c_tp_cpu 01c 4
62 struct tty * tty.t_rawq.c_tp_iop 020 4
63 unsigned char * tty.t_rawq.c_buf_cpu 024 4
64 unsigned char * tty.t_rawq.c_buf_iop 028 4
65 struct clist tty.t_canq 02c 20
66 int tty.t_canq.c_cc 02c 4
67 int tty.t_canq.c_cmax 030 4
68 int tty.t_canq.c_cfx 034 4
69 int tty.t_canq.c_clx 038 4
70 struct tty * tty.t_canq.c_tp_cpu 03c 4
71 struct tty * tty.t_canq.c_tp_iop 040 4
72 unsigned char * tty.t_canq.c_buf_cpu 044 4
73 unsigned char * tty.t_canq.c_buf_iop 048 4
74 struct clist tty.t_outq 04c 20
75 int tty.t_outq.c_cc 04c 4
76 int tty.t_outq.c_cmax 050 4
77 int tty.t_outq.c_cfx 054 4
78 int tty.t_outq.c_clx 058 4
79 struct tty * tty.t_outq.c_tp_cpu 05c 4
80 struct tty * tty.t_outq.c_tp_iop 060 4
81 unsigned char * tty.t_outq.c_buf_cpu 064 4
82 unsigned char * tty.t_outq.c_buf_iop 068 4
83 (*int)() tty.t_oproc_cpu 06c 4
84 (*int)() tty.t_oproc_iop 070 4
85 (*int)() tty.t_stopproc_cpu 074 4
86 (*int)() tty.t_stopproc_iop 078 4
87 struct thread * tty.t_rsel 07c 4
88 etc.
90 Actually, this was generated by a particular set of options. You can
92 control the formatting of each column, whether you prefer wide or fat,
93 hex or decimal, leading zeroes or whatever.
94 All you need to be able to use this is a C compiler than generates
96 BSD/GCC-style stabs. The -g option on native BSD compilers and GCC
97 should get this for you.
98 To learn more, just type a bogus option, like -\?, and a long usage
100 message will be provided. There are a fair number of possibilities.
101 If you're only a C programmer, than this is the end of the message for
103 you. You can quit right now, and if you care to, save off the source
104 and run it when you feel like it. Or not.
105 But if you're a perl programmer, then for you I have something much
107 more wondrous than just a structure offset printer.
108 You see, if you call pstruct by its other incybernation, c2ph, you have
110 a code generator that translates C code into perl code! Well, struc‐
111 ture and union declarations at least, but that's quite a bit.
112 Prior to this point, anyone programming in perl who wanted to interact
114 with C programs, like the kernel, was forced to guess the layouts of
115 the C structures, and then hardwire these into his program. Of course,
116 when you took your wonderfully crafted program to a system where the
117 sgtty structure was laid out differently, your program broke. Which is
118 a shame.
119 We've had Larry's h2ph translator, which helped, but that only works on
121 cpp symbols, not real C, which was also very much needed. What I offer
122 you is a symbolic way of getting at all the C structures. I've couched
123 them in terms of packages and functions. Consider the following pro‐
124 gram:
125 #!/usr/local/bin/perl
127 require 'syscall.ph';
129 require 'sys/time.ph';
130 require 'sys/resource.ph';
131 $ru = "\0" x &rusage'sizeof();
133 syscall(&SYS_getrusage, &RUSAGE_SELF, $ru) && die "getrusage: $!";
135 @ru = unpack($t = &rusage'typedef(), $ru);
137 $utime = $ru[ &rusage'ru_utime + &timeval'tv_sec ]
139 + ($ru[ &rusage'ru_utime + &timeval'tv_usec ]) / 1e6;
140 $stime = $ru[ &rusage'ru_stime + &timeval'tv_sec ]
142 + ($ru[ &rusage'ru_stime + &timeval'tv_usec ]) / 1e6;
143 printf "you have used %8.3fs+%8.3fu seconds.\n", $utime, $stime;
145 As you see, the name of the package is the name of the structure. Reg‐
147 ular fields are just their own names. Plus the following accessor
148 functions are provided for your convenience:
149 struct This takes no arguments, and is merely the number of first-level
151 elements in the structure. You would use this for indexing
152 into arrays of structures, perhaps like this
153 $usec = $u[ &user'u_utimer
155 + (&ITIMER_VIRTUAL * &itimerval'struct)
156 + &itimerval'it_value
157 + &timeval'tv_usec
158 ];
159 sizeof Returns the bytes in the structure, or the member if
161 you pass it an argument, such as
162 &rusage'sizeof(&rusage'ru_utime)
164 typedef This is the perl format definition for passing to pack and
166 unpack. If you ask for the typedef of a nothing, you get
167 the whole structure, otherwise you get that of the member
168 you ask for. Padding is taken care of, as is the magic to
169 guarantee that a union is unpacked into all its aliases.
170 Bitfields are not quite yet supported however.
171 offsetof This function is the byte offset into the array of that
173 member. You may wish to use this for indexing directly
174 into the packed structure with vec() if you're too lazy
175 to unpack it.
176 typeof Not to be confused with the typedef accessor function, this
178 one returns the C type of that field. This would allow
179 you to print out a nice structured pretty print of some
180 structure without knoning anything about it beforehand.
181 No args to this one is a noop. Someday I'll post such
182 a thing to dump out your u structure for you.
183 The way I see this being used is like basically this:
185 % h2ph <some_include_file.h > /usr/lib/perl/tmp.ph
187 % c2ph some_include_file.h >> /usr/lib/perl/tmp.ph
188 % install
189 It's a little tricker with c2ph because you have to get the includes
191 right. I can't know this for your system, but it's not usually too
192 terribly difficult.
193 The code isn't pretty as I mentioned -- I never thought it would be a
195 1000- line program when I started, or I might not have begun. :-) But
196 I would have been less cavalier in how the parts of the program commu‐
197 nicated with each other, etc. It might also have helped if I didn't
198 have to divine the makeup of the stabs on the fly, and then account for
199 micro differences between my compiler and gcc.
200 Anyway, here it is. Should run on perl v4 or greater. Maybe less.
202 --tom
204perl v5.8.8 2008-05-05 C2PH(1)