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:
13 -w wide; short for: type_width=45 member_width=35 offset_width=8
15 -x hex; short for: offset_fmt=x offset_width=08 size_fmt=x size_width=04
16 -n do not generate perl code (default when invoked as pstruct)
18 -p generate perl code (default when invoked as c2ph)
19 -v generate perl code, with C decls as comments
20 -i do NOT recompute sizes for intrinsic datatypes
22 -a dump information on intrinsics also
23 -t trace execution
25 -d spew reams of debugging output
26 -slist give comma-separated list a structures to dump
28
30 The following is the old c2ph.doc documentation by Tom Christiansen
31 <tchrist@perl.com> Date: 25 Jul 91 08:10:21 GMT
32 Once upon a time, I wrote a program called pstruct. It was a perl
34 program that tried to parse out C structures and display their member
35 offsets for you. This was especially useful for people looking at
36 binary dumps or poking around the kernel.
37 Pstruct was not a pretty program. Neither was it particularly robust.
39 The problem, you see, was that the C compiler was much better at
40 parsing C than I could ever hope to be.
41 So I got smart: I decided to be lazy and let the C compiler parse the
43 C, which would spit out debugger stabs for me to read. These were much
44 easier to parse. It's still not a pretty program, but at least it's
45 more robust.
46 Pstruct takes any .c or .h files, or preferably .s ones, since that's
48 the format it is going to massage them into anyway, and spits out
49 listings like this:
50 struct tty {
52 int tty.t_locker 000 4
53 int tty.t_mutex_index 004 4
54 struct tty * tty.t_tp_virt 008 4
55 struct clist tty.t_rawq 00c 20
56 int tty.t_rawq.c_cc 00c 4
57 int tty.t_rawq.c_cmax 010 4
58 int tty.t_rawq.c_cfx 014 4
59 int tty.t_rawq.c_clx 018 4
60 struct tty * tty.t_rawq.c_tp_cpu 01c 4
61 struct tty * tty.t_rawq.c_tp_iop 020 4
62 unsigned char * tty.t_rawq.c_buf_cpu 024 4
63 unsigned char * tty.t_rawq.c_buf_iop 028 4
64 struct clist tty.t_canq 02c 20
65 int tty.t_canq.c_cc 02c 4
66 int tty.t_canq.c_cmax 030 4
67 int tty.t_canq.c_cfx 034 4
68 int tty.t_canq.c_clx 038 4
69 struct tty * tty.t_canq.c_tp_cpu 03c 4
70 struct tty * tty.t_canq.c_tp_iop 040 4
71 unsigned char * tty.t_canq.c_buf_cpu 044 4
72 unsigned char * tty.t_canq.c_buf_iop 048 4
73 struct clist tty.t_outq 04c 20
74 int tty.t_outq.c_cc 04c 4
75 int tty.t_outq.c_cmax 050 4
76 int tty.t_outq.c_cfx 054 4
77 int tty.t_outq.c_clx 058 4
78 struct tty * tty.t_outq.c_tp_cpu 05c 4
79 struct tty * tty.t_outq.c_tp_iop 060 4
80 unsigned char * tty.t_outq.c_buf_cpu 064 4
81 unsigned char * tty.t_outq.c_buf_iop 068 4
82 (*int)() tty.t_oproc_cpu 06c 4
83 (*int)() tty.t_oproc_iop 070 4
84 (*int)() tty.t_stopproc_cpu 074 4
85 (*int)() tty.t_stopproc_iop 078 4
86 struct thread * tty.t_rsel 07c 4
87 etc.
89 Actually, this was generated by a particular set of options. You can
91 control the formatting of each column, whether you prefer wide or fat,
92 hex or decimal, leading zeroes or whatever.
93 All you need to be able to use this is a C compiler than generates
95 BSD/GCC-style stabs. The -g option on native BSD compilers and GCC
96 should get this for you.
97 To learn more, just type a bogus option, like -\?, and a long usage
99 message will be provided. There are a fair number of possibilities.
100 If you're only a C programmer, than this is the end of the message for
102 you. You can quit right now, and if you care to, save off the source
103 and run it when you feel like it. Or not.
104 But if you're a perl programmer, then for you I have something much
106 more wondrous than just a structure offset printer.
107 You see, if you call pstruct by its other incybernation, c2ph, you have
109 a code generator that translates C code into perl code! Well,
110 structure and union declarations at least, but that's quite a bit.
111 Prior to this point, anyone programming in perl who wanted to interact
113 with C programs, like the kernel, was forced to guess the layouts of
114 the C structures, and then hardwire these into his program. Of course,
115 when you took your wonderfully crafted program to a system where the
116 sgtty structure was laid out differently, your program broke. Which is
117 a shame.
118 We've had Larry's h2ph translator, which helped, but that only works on
120 cpp symbols, not real C, which was also very much needed. What I offer
121 you is a symbolic way of getting at all the C structures. I've couched
122 them in terms of packages and functions. Consider the following
123 program:
124 #!/usr/local/bin/perl
126 require 'syscall.ph';
128 require 'sys/time.ph';
129 require 'sys/resource.ph';
130 $ru = "\0" x &rusage'sizeof();
132 syscall(&SYS_getrusage, &RUSAGE_SELF, $ru) && die "getrusage: $!";
134 @ru = unpack($t = &rusage'typedef(), $ru);
136 $utime = $ru[ &rusage'ru_utime + &timeval'tv_sec ]
138 + ($ru[ &rusage'ru_utime + &timeval'tv_usec ]) / 1e6;
139 $stime = $ru[ &rusage'ru_stime + &timeval'tv_sec ]
141 + ($ru[ &rusage'ru_stime + &timeval'tv_usec ]) / 1e6;
142 printf "you have used %8.3fs+%8.3fu seconds.\n", $utime, $stime;
144 As you see, the name of the package is the name of the structure.
146 Regular fields are just their own names. Plus the following accessor
147 functions are provided for your convenience:
148 struct This takes no arguments, and is merely the number of first-level
150 elements in the structure. You would use this for indexing
151 into arrays of structures, perhaps like this
152 $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
197 communicated with each other, etc. It might also have helped if I
198 didn't have to divine the makeup of the stabs on the fly, and then
199 account for micro differences between my compiler and gcc.
200 Anyway, here it is. Should run on perl v4 or greater. Maybe less.
202 --tom
204perl v5.10.1 2017-03-22 C2PH(1)