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properly define perl_parse() return value
[perl5.git] / pod / perlembed.pod
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1=head1 NAME
2
cb1a09d0 3perlembed - how to embed perl in your C program
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4
5=head1 DESCRIPTION
6
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7=head2 PREAMBLE
8
9Do you want to:
10
11=over 5
12
96dbc785 13=item B<Use C from Perl?>
cb1a09d0 14
4929bf7b 15Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>.
cb1a09d0 16
54310121 17=item B<Use a Unix program from Perl?>
cb1a09d0 18
5f05dabc 19Read about back-quotes and about C<system> and C<exec> in L<perlfunc>.
cb1a09d0 20
96dbc785 21=item B<Use Perl from Perl?>
cb1a09d0 22
5e6bcc01 23Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require>
e010571f 24and L<perlfunc/use>.
cb1a09d0 25
96dbc785 26=item B<Use C from C?>
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27
28Rethink your design.
29
96dbc785 30=item B<Use Perl from C?>
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31
32Read on...
33
34=back
35
36=head2 ROADMAP
37
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38=over 5
39
551e1d92 40=item *
cb1a09d0 41
551e1d92 42Compiling your C program
cb1a09d0 43
551e1d92 44=item *
cb1a09d0 45
551e1d92 46Adding a Perl interpreter to your C program
cb1a09d0 47
551e1d92 48=item *
cb1a09d0 49
551e1d92 50Calling a Perl subroutine from your C program
cb1a09d0 51
551e1d92 52=item *
cb1a09d0 53
551e1d92 54Evaluating a Perl statement from your C program
a6006777 55
551e1d92 56=item *
8ebc5c01 57
551e1d92
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58Performing Perl pattern matches and substitutions from your C program
59
60=item *
61
62Fiddling with the Perl stack from your C program
63
64=item *
65
66Maintaining a persistent interpreter
67
68=item *
69
70Maintaining multiple interpreter instances
71
72=item *
73
74Using Perl modules, which themselves use C libraries, from your C program
75
76=item *
77
78Embedding Perl under Win32
96dbc785 79
5e6bcc01 80=back
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81
82=head2 Compiling your C program
83
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84If you have trouble compiling the scripts in this documentation,
85you're not alone. The cardinal rule: COMPILE THE PROGRAMS IN EXACTLY
86THE SAME WAY THAT YOUR PERL WAS COMPILED. (Sorry for yelling.)
cb1a09d0 87
8a7dc658 88Also, every C program that uses Perl must link in the I<perl library>.
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89What's that, you ask? Perl is itself written in C; the perl library
90is the collection of compiled C programs that were used to create your
91perl executable (I</usr/bin/perl> or equivalent). (Corollary: you
92can't use Perl from your C program unless Perl has been compiled on
93your machine, or installed properly--that's why you shouldn't blithely
94copy Perl executables from machine to machine without also copying the
95I<lib> directory.)
96
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97When you use Perl from C, your C program will--usually--allocate,
98"run", and deallocate a I<PerlInterpreter> object, which is defined by
99the perl library.
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100
101If your copy of Perl is recent enough to contain this documentation
a6006777 102(version 5.002 or later), then the perl library (and I<EXTERN.h> and
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103I<perl.h>, which you'll also need) will reside in a directory
104that looks like this:
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105
106 /usr/local/lib/perl5/your_architecture_here/CORE
107
108or perhaps just
109
110 /usr/local/lib/perl5/CORE
111
112or maybe something like
113
114 /usr/opt/perl5/CORE
115
116Execute this statement for a hint about where to find CORE:
117
96dbc785 118 perl -MConfig -e 'print $Config{archlib}'
cb1a09d0 119
54310121 120Here's how you'd compile the example in the next section,
5a0de581 121L</Adding a Perl interpreter to your C program>, on my Linux box:
cb1a09d0 122
54310121 123 % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include
8a7dc658 124 -I/usr/local/lib/perl5/i586-linux/5.003/CORE
54310121 125 -L/usr/local/lib/perl5/i586-linux/5.003/CORE
8a7dc658 126 -o interp interp.c -lperl -lm
cb1a09d0 127
5e6bcc01 128(That's all one line.) On my DEC Alpha running old 5.003_05, the
e010571f 129incantation is a bit different:
8a7dc658 130
b78ed007 131 % cc -O2 -Olimit 2900 -I/usr/local/include
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132 -I/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE
133 -L/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE -L/usr/local/lib
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134 -D__LANGUAGE_C__ -D_NO_PROTO -o interp interp.c -lperl -lm
135
136How can you figure out what to add? Assuming your Perl is post-5.001,
137execute a C<perl -V> command and pay special attention to the "cc" and
54310121 138"ccflags" information.
8a7dc658 139
54310121 140You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for
8a7dc658 141your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what
54310121 142to use.
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143
144You'll also have to choose the appropriate library directory
145(I</usr/local/lib/...>) for your machine. If your compiler complains
146that certain functions are undefined, or that it can't locate
147I<-lperl>, then you need to change the path following the C<-L>. If it
148complains that it can't find I<EXTERN.h> and I<perl.h>, you need to
149change the path following the C<-I>.
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150
151You may have to add extra libraries as well. Which ones?
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152Perhaps those printed by
153
154 perl -MConfig -e 'print $Config{libs}'
155
54310121 156Provided your perl binary was properly configured and installed the
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157B<ExtUtils::Embed> module will determine all of this information for
158you:
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159
160 % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
161
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162If the B<ExtUtils::Embed> module isn't part of your Perl distribution,
163you can retrieve it from
4b05bc8e 164L<http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/>
f224927c 165(If this documentation came from your Perl distribution, then you're
8a7dc658 166running 5.004 or better and you already have it.)
96dbc785 167
8a7dc658 168The B<ExtUtils::Embed> kit on CPAN also contains all source code for
54310121 169the examples in this document, tests, additional examples and other
8a7dc658 170information you may find useful.
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171
172=head2 Adding a Perl interpreter to your C program
173
174In a sense, perl (the C program) is a good example of embedding Perl
175(the language), so I'll demonstrate embedding with I<miniperlmain.c>,
353c6505 176included in the source distribution. Here's a bastardized, non-portable
8a7dc658 177version of I<miniperlmain.c> containing the essentials of embedding:
cb1a09d0 178
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179 #include <EXTERN.h> /* from the Perl distribution */
180 #include <perl.h> /* from the Perl distribution */
96dbc785 181
5e6bcc01 182 static PerlInterpreter *my_perl; /*** The Perl interpreter ***/
96dbc785 183
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184 int main(int argc, char **argv, char **env)
185 {
1ccffcf5 186 PERL_SYS_INIT3(&argc,&argv,&env);
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187 my_perl = perl_alloc();
188 perl_construct(my_perl);
d95b23b2 189 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
96dbc785 190 perl_parse(my_perl, NULL, argc, argv, (char **)NULL);
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191 perl_run(my_perl);
192 perl_destruct(my_perl);
193 perl_free(my_perl);
1ccffcf5 194 PERL_SYS_TERM();
0301e899 195 exit(EXIT_SUCCESS);
5e6bcc01 196 }
cb1a09d0 197
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198Notice that we don't use the C<env> pointer. Normally handed to
199C<perl_parse> as its final argument, C<env> here is replaced by
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200C<NULL>, which means that the current environment will be used.
201
202The macros PERL_SYS_INIT3() and PERL_SYS_TERM() provide system-specific
203tune up of the C runtime environment necessary to run Perl interpreters;
204they should only be called once regardless of how many interpreters you
205create or destroy. Call PERL_SYS_INIT3() before you create your first
206interpreter, and PERL_SYS_TERM() after you free your last interpreter.
207
208Since PERL_SYS_INIT3() may change C<env>, it may be more appropriate to
209provide C<env> as an argument to perl_parse().
96dbc785 210
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211Also notice that no matter what arguments you pass to perl_parse(),
212PERL_SYS_INIT3() must be invoked on the C main() argc, argv and env and
213only once.
214
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215Mind that argv[argc] must be NULL, same as those passed to a main
216function in C.
217
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218Now compile this program (I'll call it I<interp.c>) into an executable:
219
96dbc785 220 % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
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221
222After a successful compilation, you'll be able to use I<interp> just
223like perl itself:
224
225 % interp
226 print "Pretty Good Perl \n";
227 print "10890 - 9801 is ", 10890 - 9801;
228 <CTRL-D>
229 Pretty Good Perl
230 10890 - 9801 is 1089
231
232or
233
234 % interp -e 'printf("%x", 3735928559)'
235 deadbeef
236
237You can also read and execute Perl statements from a file while in the
238midst of your C program, by placing the filename in I<argv[1]> before
e010571f 239calling I<perl_run>.
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240
241=head2 Calling a Perl subroutine from your C program
242
4929bf7b 243To call individual Perl subroutines, you can use any of the B<call_*>
7b8d334a 244functions documented in L<perlcall>.
4929bf7b 245In this example we'll use C<call_argv>.
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246
247That's shown below, in a program I'll call I<showtime.c>.
248
cb1a09d0 249 #include <EXTERN.h>
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250 #include <perl.h>
251
252 static PerlInterpreter *my_perl;
253
c07a80fd 254 int main(int argc, char **argv, char **env)
cb1a09d0 255 {
8ebc5c01 256 char *args[] = { NULL };
1ccffcf5 257 PERL_SYS_INIT3(&argc,&argv,&env);
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258 my_perl = perl_alloc();
259 perl_construct(my_perl);
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260
261 perl_parse(my_perl, NULL, argc, argv, NULL);
d95b23b2 262 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
96dbc785 263
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264 /*** skipping perl_run() ***/
265
4929bf7b 266 call_argv("showtime", G_DISCARD | G_NOARGS, args);
8ebc5c01 267
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268 perl_destruct(my_perl);
269 perl_free(my_perl);
1ccffcf5 270 PERL_SYS_TERM();
0301e899 271 exit(EXIT_SUCCESS);
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272 }
273
274where I<showtime> is a Perl subroutine that takes no arguments (that's the
96dbc785 275I<G_NOARGS>) and for which I'll ignore the return value (that's the
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276I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>.
277
278I'll define the I<showtime> subroutine in a file called I<showtime.pl>:
279
5e6bcc01 280 print "I shan't be printed.";
96dbc785 281
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282 sub showtime {
283 print time;
284 }
cb1a09d0 285
5e6bcc01 286Simple enough. Now compile and run:
96dbc785 287
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288 % cc -o showtime showtime.c \
289 `perl -MExtUtils::Embed -e ccopts -e ldopts`
290 % showtime showtime.pl
291 818284590
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292
293yielding the number of seconds that elapsed between January 1, 1970
8a7dc658 294(the beginning of the Unix epoch), and the moment I began writing this
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295sentence.
296
5e6bcc01 297In this particular case we don't have to call I<perl_run>, as we set
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298the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in
299perl_destruct.
8ebc5c01 300
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301If you want to pass arguments to the Perl subroutine, you can add
302strings to the C<NULL>-terminated C<args> list passed to
4929bf7b 303I<call_argv>. For other data types, or to examine return values,
13a2d996 304you'll need to manipulate the Perl stack. That's demonstrated in
5a0de581 305L</Fiddling with the Perl stack from your C program>.
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306
307=head2 Evaluating a Perl statement from your C program
308
137443ea 309Perl provides two API functions to evaluate pieces of Perl code.
4929bf7b 310These are L<perlapi/eval_sv> and L<perlapi/eval_pv>.
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311
312Arguably, these are the only routines you'll ever need to execute
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313snippets of Perl code from within your C program. Your code can be as
314long as you wish; it can contain multiple statements; it can employ
315L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to
316include external Perl files.
cb1a09d0 317
4929bf7b 318I<eval_pv> lets us evaluate individual Perl strings, and then
96dbc785 319extract variables for coercion into C types. The following program,
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320I<string.c>, executes three Perl strings, extracting an C<int> from
321the first, a C<float> from the second, and a C<char *> from the third.
322
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323 #include <EXTERN.h>
324 #include <perl.h>
c47ff5f1 325
5e6bcc01 326 static PerlInterpreter *my_perl;
c47ff5f1 327
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328 main (int argc, char **argv, char **env)
329 {
0301e899 330 char *embedding[] = { "", "-e", "0", NULL };
c47ff5f1 331
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332 PERL_SYS_INIT3(&argc,&argv,&env);
333 my_perl = perl_alloc();
334 perl_construct( my_perl );
c47ff5f1 335
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336 perl_parse(my_perl, NULL, 3, embedding, NULL);
337 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
338 perl_run(my_perl);
c47ff5f1 339
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340 /** Treat $a as an integer **/
341 eval_pv("$a = 3; $a **= 2", TRUE);
342 printf("a = %d\n", SvIV(get_sv("a", 0)));
c47ff5f1 343
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344 /** Treat $a as a float **/
345 eval_pv("$a = 3.14; $a **= 2", TRUE);
346 printf("a = %f\n", SvNV(get_sv("a", 0)));
c47ff5f1 347
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348 /** Treat $a as a string **/
349 eval_pv(
350 "$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE);
351 printf("a = %s\n", SvPV_nolen(get_sv("a", 0)));
c47ff5f1 352
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353 perl_destruct(my_perl);
354 perl_free(my_perl);
355 PERL_SYS_TERM();
356 }
cb1a09d0 357
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358All of those strange functions with I<sv> in their names help convert Perl
359scalars to C types. They're described in L<perlguts> and L<perlapi>.
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360
361If you compile and run I<string.c>, you'll see the results of using
362I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and
363I<SvPV()> to create a string:
364
365 a = 9
366 a = 9.859600
367 a = Just Another Perl Hacker
368
8f183262 369In the example above, we've created a global variable to temporarily
353c6505 370store the computed value of our eval'ed expression. It is also
8f183262 371possible and in most cases a better strategy to fetch the return value
4929bf7b 372from I<eval_pv()> instead. Example:
8f183262 373
8f183262 374 ...
4929bf7b 375 SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE);
1c5b513e 376 printf("%s\n", SvPV_nolen(val));
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377 ...
378
379This way, we avoid namespace pollution by not creating global
380variables and we've simplified our code as well.
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381
382=head2 Performing Perl pattern matches and substitutions from your C program
383
4929bf7b 384The I<eval_sv()> function lets us evaluate strings of Perl code, so we can
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385define some functions that use it to "specialize" in matches and
386substitutions: I<match()>, I<substitute()>, and I<matches()>.
387
e010571f 388 I32 match(SV *string, char *pattern);
cb1a09d0 389
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390Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which
391in your C program might appear as "/\\b\\w*\\b/"), match()
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392returns 1 if the string matches the pattern and 0 otherwise.
393
1f05cdcd 394 int substitute(SV **string, char *pattern);
cb1a09d0 395
1f05cdcd 396Given a pointer to an C<SV> and an C<=~> operation (e.g.,
8a7dc658 397C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string
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398within the C<SV> as according to the operation, returning the number of
399substitutions made.
cb1a09d0 400
c70927a6 401 SSize_t matches(SV *string, char *pattern, AV **matches);
cb1a09d0 402
1f05cdcd 403Given an C<SV>, a pattern, and a pointer to an empty C<AV>,
90fdbbb7 404matches() evaluates C<$string =~ $pattern> in a list context, and
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405fills in I<matches> with the array elements, returning the number of matches
406found.
cb1a09d0 407
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408Here's a sample program, I<match.c>, that uses all three (long lines have
409been wrapped here):
cb1a09d0 410
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411 #include <EXTERN.h>
412 #include <perl.h>
c47ff5f1 413
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414 static PerlInterpreter *my_perl;
415
4929bf7b 416 /** my_eval_sv(code, error_check)
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417 ** kinda like eval_sv(),
418 ** but we pop the return value off the stack
1f05cdcd 419 **/
4929bf7b 420 SV* my_eval_sv(SV *sv, I32 croak_on_error)
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421 {
422 dSP;
423 SV* retval;
1c5b513e 424
c47ff5f1 425
924508f0 426 PUSHMARK(SP);
4929bf7b 427 eval_sv(sv, G_SCALAR);
c47ff5f1 428
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429 SPAGAIN;
430 retval = POPs;
431 PUTBACK;
c47ff5f1 432
9cde0e7f 433 if (croak_on_error && SvTRUE(ERRSV))
1c5b513e 434 croak(SvPVx_nolen(ERRSV));
c47ff5f1 435
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436 return retval;
437 }
c47ff5f1 438
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439 /** match(string, pattern)
440 **
441 ** Used for matches in a scalar context.
442 **
443 ** Returns 1 if the match was successful; 0 otherwise.
444 **/
c47ff5f1 445
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446 I32 match(SV *string, char *pattern)
447 {
561b68a9 448 SV *command = newSV(0), *retval;
c47ff5f1 449
1f05cdcd 450 sv_setpvf(command, "my $string = '%s'; $string =~ %s",
1c5b513e 451 SvPV_nolen(string), pattern);
c47ff5f1 452
4929bf7b 453 retval = my_eval_sv(command, TRUE);
1f05cdcd 454 SvREFCNT_dec(command);
c47ff5f1 455
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456 return SvIV(retval);
457 }
c47ff5f1 458
1f05cdcd
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459 /** substitute(string, pattern)
460 **
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461 ** Used for =~ operations that
462 ** modify their left-hand side (s/// and tr///)
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463 **
464 ** Returns the number of successful matches, and
465 ** modifies the input string if there were any.
466 **/
c47ff5f1 467
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468 I32 substitute(SV **string, char *pattern)
469 {
561b68a9 470 SV *command = newSV(0), *retval;
c47ff5f1 471
1f05cdcd 472 sv_setpvf(command, "$string = '%s'; ($string =~ %s)",
1c5b513e 473 SvPV_nolen(*string), pattern);
c47ff5f1 474
4929bf7b 475 retval = my_eval_sv(command, TRUE);
1f05cdcd 476 SvREFCNT_dec(command);
c47ff5f1 477
64ace3f8 478 *string = get_sv("string", 0);
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479 return SvIV(retval);
480 }
c47ff5f1 481
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482 /** matches(string, pattern, matches)
483 **
90fdbbb7 484 ** Used for matches in a list context.
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485 **
486 ** Returns the number of matches,
487 ** and fills in **matches with the matching substrings
488 **/
c47ff5f1 489
c70927a6 490 SSize_t matches(SV *string, char *pattern, AV **match_list)
1f05cdcd 491 {
561b68a9 492 SV *command = newSV(0);
c70927a6 493 SSize_t num_matches;
c47ff5f1 494
1f05cdcd 495 sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)",
1c5b513e 496 SvPV_nolen(string), pattern);
c47ff5f1 497
4929bf7b 498 my_eval_sv(command, TRUE);
1f05cdcd 499 SvREFCNT_dec(command);
c47ff5f1 500
cbfd0a87 501 *match_list = get_av("array", 0);
23aa77bc 502 num_matches = av_top_index(*match_list) + 1;
c47ff5f1 503
cb1a09d0 504 return num_matches;
1f05cdcd 505 }
c47ff5f1 506
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507 main (int argc, char **argv, char **env)
508 {
0301e899 509 char *embedding[] = { "", "-e", "0", NULL };
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510 AV *match_list;
511 I32 num_matches, i;
7fef744d 512 SV *text;
c47ff5f1 513
1ccffcf5 514 PERL_SYS_INIT3(&argc,&argv,&env);
7fef744d 515 my_perl = perl_alloc();
1f05cdcd 516 perl_construct(my_perl);
96dbc785 517 perl_parse(my_perl, NULL, 3, embedding, NULL);
d95b23b2 518 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
c47ff5f1 519
561b68a9 520 text = newSV(0);
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521 sv_setpv(text, "When he is at a convenience store and the "
522 "bill comes to some amount like 76 cents, Maynard is "
523 "aware that there is something he *should* do, something "
524 "that will enable him to get back a quarter, but he has "
525 "no idea *what*. He fumbles through his red squeezey "
526 "changepurse and gives the boy three extra pennies with "
527 "his dollar, hoping that he might luck into the correct "
528 "amount. The boy gives him back two of his own pennies "
529 "and then the big shiny quarter that is his prize. "
530 "-RICHH");
c47ff5f1 531
96dbc785 532 if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/
1f05cdcd 533 printf("match: Text contains the word 'quarter'.\n\n");
96dbc785 534 else
1f05cdcd 535 printf("match: Text doesn't contain the word 'quarter'.\n\n");
c47ff5f1 536
96dbc785 537 if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/
1f05cdcd 538 printf("match: Text contains the word 'eighth'.\n\n");
96dbc785 539 else
1f05cdcd 540 printf("match: Text doesn't contain the word 'eighth'.\n\n");
c47ff5f1 541
96dbc785
PP
542 /** Match all occurrences of /wi../ **/
543 num_matches = matches(text, "m/(wi..)/g", &match_list);
544 printf("matches: m/(wi..)/g found %d matches...\n", num_matches);
c47ff5f1 545
96dbc785 546 for (i = 0; i < num_matches; i++)
5e6bcc01
GID
547 printf("match: %s\n",
548 SvPV_nolen(*av_fetch(match_list, i, FALSE)));
cb1a09d0 549 printf("\n");
c47ff5f1 550
96dbc785
PP
551 /** Remove all vowels from text **/
552 num_matches = substitute(&text, "s/[aeiou]//gi");
cb1a09d0 553 if (num_matches) {
c70927a6
FC
554 printf("substitute: s/[aeiou]//gi...%lu substitutions made.\n",
555 (unsigned long)num_matches);
1c5b513e 556 printf("Now text is: %s\n\n", SvPV_nolen(text));
cb1a09d0 557 }
c47ff5f1 558
96dbc785
PP
559 /** Attempt a substitution **/
560 if (!substitute(&text, "s/Perl/C/")) {
1f05cdcd 561 printf("substitute: s/Perl/C...No substitution made.\n\n");
cb1a09d0 562 }
c47ff5f1 563
1f05cdcd 564 SvREFCNT_dec(text);
9cde0e7f 565 PL_perl_destruct_level = 1;
cb1a09d0
AD
566 perl_destruct(my_perl);
567 perl_free(my_perl);
1ccffcf5 568 PERL_SYS_TERM();
1f05cdcd 569 }
cb1a09d0 570
96dbc785 571which produces the output (again, long lines have been wrapped here)
cb1a09d0 572
5e6bcc01 573 match: Text contains the word 'quarter'.
96dbc785 574
5e6bcc01 575 match: Text doesn't contain the word 'eighth'.
96dbc785 576
5e6bcc01
GID
577 matches: m/(wi..)/g found 2 matches...
578 match: will
579 match: with
96dbc785 580
5e6bcc01
GID
581 substitute: s/[aeiou]//gi...139 substitutions made.
582 Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts,
583 Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt
584 bck qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd
585 gvs th by thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct
586 mnt. Th by gvs hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s
587 hs prz. -RCHH
96dbc785 588
5e6bcc01 589 substitute: s/Perl/C...No substitution made.
96dbc785 590
cb1a09d0
AD
591=head2 Fiddling with the Perl stack from your C program
592
593When trying to explain stacks, most computer science textbooks mumble
594something about spring-loaded columns of cafeteria plates: the last
595thing you pushed on the stack is the first thing you pop off. That'll
596do for our purposes: your C program will push some arguments onto "the Perl
597stack", shut its eyes while some magic happens, and then pop the
598results--the return value of your Perl subroutine--off the stack.
96dbc785 599
cb1a09d0
AD
600First you'll need to know how to convert between C types and Perl
601types, with newSViv() and sv_setnv() and newAV() and all their
4929bf7b 602friends. They're described in L<perlguts> and L<perlapi>.
cb1a09d0
AD
603
604Then you'll need to know how to manipulate the Perl stack. That's
605described in L<perlcall>.
606
96dbc785 607Once you've understood those, embedding Perl in C is easy.
cb1a09d0 608
54310121 609Because C has no builtin function for integer exponentiation, let's
cb1a09d0 610make Perl's ** operator available to it (this is less useful than it
5f05dabc 611sounds, because Perl implements ** with C's I<pow()> function). First
cb1a09d0
AD
612I'll create a stub exponentiation function in I<power.pl>:
613
614 sub expo {
615 my ($a, $b) = @_;
616 return $a ** $b;
617 }
618
619Now I'll create a C program, I<power.c>, with a function
620I<PerlPower()> that contains all the perlguts necessary to push the
621two arguments into I<expo()> and to pop the return value out. Take a
622deep breath...
623
5e6bcc01
GID
624 #include <EXTERN.h>
625 #include <perl.h>
96dbc785 626
5e6bcc01 627 static PerlInterpreter *my_perl;
96dbc785 628
5e6bcc01
GID
629 static void
630 PerlPower(int a, int b)
631 {
632 dSP; /* initialize stack pointer */
633 ENTER; /* everything created after here */
634 SAVETMPS; /* ...is a temporary variable. */
635 PUSHMARK(SP); /* remember the stack pointer */
636 XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */
637 XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */
638 PUTBACK; /* make local stack pointer global */
639 call_pv("expo", G_SCALAR); /* call the function */
640 SPAGAIN; /* refresh stack pointer */
641 /* pop the return value from stack */
642 printf ("%d to the %dth power is %d.\n", a, b, POPi);
643 PUTBACK;
644 FREETMPS; /* free that return value */
645 LEAVE; /* ...and the XPUSHed "mortal" args.*/
646 }
96dbc785 647
5e6bcc01
GID
648 int main (int argc, char **argv, char **env)
649 {
0301e899 650 char *my_argv[] = { "", "power.pl", NULL };
96dbc785 651
5e6bcc01
GID
652 PERL_SYS_INIT3(&argc,&argv,&env);
653 my_perl = perl_alloc();
654 perl_construct( my_perl );
96dbc785 655
5e6bcc01
GID
656 perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
657 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
658 perl_run(my_perl);
96dbc785 659
5e6bcc01 660 PerlPower(3, 4); /*** Compute 3 ** 4 ***/
96dbc785 661
5e6bcc01
GID
662 perl_destruct(my_perl);
663 perl_free(my_perl);
664 PERL_SYS_TERM();
0301e899 665 exit(EXIT_SUCCESS);
5e6bcc01 666 }
96dbc785 667
cb1a09d0
AD
668
669
670Compile and run:
671
96dbc785
PP
672 % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
673
674 % power
cb1a09d0
AD
675 3 to the 4th power is 81.
676
a6006777
PP
677=head2 Maintaining a persistent interpreter
678
8a7dc658
JO
679When developing interactive and/or potentially long-running
680applications, it's a good idea to maintain a persistent interpreter
681rather than allocating and constructing a new interpreter multiple
682times. The major reason is speed: since Perl will only be loaded into
54310121 683memory once.
8a7dc658
JO
684
685However, you have to be more cautious with namespace and variable
686scoping when using a persistent interpreter. In previous examples
687we've been using global variables in the default package C<main>. We
688knew exactly what code would be run, and assumed we could avoid
689variable collisions and outrageous symbol table growth.
690
691Let's say your application is a server that will occasionally run Perl
692code from some arbitrary file. Your server has no way of knowing what
693code it's going to run. Very dangerous.
694
695If the file is pulled in by C<perl_parse()>, compiled into a newly
696constructed interpreter, and subsequently cleaned out with
697C<perl_destruct()> afterwards, you're shielded from most namespace
698troubles.
699
700One way to avoid namespace collisions in this scenario is to translate
701the filename into a guaranteed-unique package name, and then compile
e010571f 702the code into that package using L<perlfunc/eval>. In the example
8a7dc658
JO
703below, each file will only be compiled once. Or, the application
704might choose to clean out the symbol table associated with the file
4929bf7b 705after it's no longer needed. Using L<perlapi/call_argv>, We'll
8a7dc658
JO
706call the subroutine C<Embed::Persistent::eval_file> which lives in the
707file C<persistent.pl> and pass the filename and boolean cleanup/cache
a6006777
PP
708flag as arguments.
709
8a7dc658
JO
710Note that the process will continue to grow for each file that it
711uses. In addition, there might be C<AUTOLOAD>ed subroutines and other
712conditions that cause Perl's symbol table to grow. You might want to
713add some logic that keeps track of the process size, or restarts
714itself after a certain number of requests, to ensure that memory
715consumption is minimized. You'll also want to scope your variables
e010571f 716with L<perlfunc/my> whenever possible.
a6006777 717
54310121 718
a6006777
PP
719 package Embed::Persistent;
720 #persistent.pl
54310121 721
a6006777 722 use strict;
77ca0c92 723 our %Cache;
1ee082b7 724 use Symbol qw(delete_package);
54310121 725
a6006777
PP
726 sub valid_package_name {
727 my($string) = @_;
728 $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg;
729 # second pass only for words starting with a digit
730 $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg;
54310121 731
a6006777
PP
732 # Dress it up as a real package name
733 $string =~ s|/|::|g;
734 return "Embed" . $string;
735 }
54310121 736
a6006777
PP
737 sub eval_file {
738 my($filename, $delete) = @_;
739 my $package = valid_package_name($filename);
740 my $mtime = -M $filename;
741 if(defined $Cache{$package}{mtime}
742 &&
54310121 743 $Cache{$package}{mtime} <= $mtime)
a6006777 744 {
54310121 745 # we have compiled this subroutine already,
8ebc5c01
PP
746 # it has not been updated on disk, nothing left to do
747 print STDERR "already compiled $package->handler\n";
a6006777
PP
748 }
749 else {
8ebc5c01
PP
750 local *FH;
751 open FH, $filename or die "open '$filename' $!";
752 local($/) = undef;
753 my $sub = <FH>;
754 close FH;
54310121 755
8ebc5c01
PP
756 #wrap the code into a subroutine inside our unique package
757 my $eval = qq{package $package; sub handler { $sub; }};
758 {
759 # hide our variables within this block
760 my($filename,$mtime,$package,$sub);
761 eval $eval;
762 }
763 die $@ if $@;
54310121 764
8ebc5c01
PP
765 #cache it unless we're cleaning out each time
766 $Cache{$package}{mtime} = $mtime unless $delete;
a6006777 767 }
54310121 768
a6006777
PP
769 eval {$package->handler;};
770 die $@ if $@;
54310121 771
a6006777 772 delete_package($package) if $delete;
54310121 773
a6006777
PP
774 #take a look if you want
775 #print Devel::Symdump->rnew($package)->as_string, $/;
776 }
54310121 777
a6006777 778 1;
54310121 779
a6006777
PP
780 __END__
781
782 /* persistent.c */
54310121
PP
783 #include <EXTERN.h>
784 #include <perl.h>
785
5e6bcc01
GID
786 /* 1 = clean out filename's symbol table after each request,
787 0 = don't
788 */
a6006777
PP
789 #ifndef DO_CLEAN
790 #define DO_CLEAN 0
791 #endif
54310121 792
2307c6d0
SB
793 #define BUFFER_SIZE 1024
794
7fef744d 795 static PerlInterpreter *my_perl = NULL;
54310121 796
a6006777
PP
797 int
798 main(int argc, char **argv, char **env)
799 {
0301e899 800 char *embedding[] = { "", "persistent.pl", NULL };
a6006777 801 char *args[] = { "", DO_CLEAN, NULL };
2307c6d0 802 char filename[BUFFER_SIZE];
0301e899 803 int failing, exitstatus;
54310121 804
1ccffcf5 805 PERL_SYS_INIT3(&argc,&argv,&env);
7fef744d 806 if((my_perl = perl_alloc()) == NULL) {
8ebc5c01 807 fprintf(stderr, "no memory!");
0301e899 808 exit(EXIT_FAILURE);
a6006777 809 }
7fef744d 810 perl_construct(my_perl);
54310121 811
5e6bcc01
GID
812 PL_origalen = 1; /* don't let $0 assignment update the
813 proctitle or embedding[0] */
0301e899 814 failing = perl_parse(my_perl, NULL, 2, embedding, NULL);
d95b23b2 815 PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
0301e899
Z
816 if(!failing)
817 failing = perl_run(my_perl);
818 if(!failing) {
2307c6d0
SB
819 while(printf("Enter file name: ") &&
820 fgets(filename, BUFFER_SIZE, stdin)) {
54310121 821
2307c6d0 822 filename[strlen(filename)-1] = '\0'; /* strip \n */
5e6bcc01
GID
823 /* call the subroutine,
824 passing it the filename as an argument */
8ebc5c01 825 args[0] = filename;
4929bf7b 826 call_argv("Embed::Persistent::eval_file",
8ebc5c01 827 G_DISCARD | G_EVAL, args);
54310121 828
8ebc5c01 829 /* check $@ */
9cde0e7f 830 if(SvTRUE(ERRSV))
1c5b513e 831 fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV));
8ebc5c01 832 }
a6006777 833 }
54310121 834
9cde0e7f 835 PL_perl_destruct_level = 0;
0301e899 836 exitstatus = perl_destruct(my_perl);
7fef744d 837 perl_free(my_perl);
1ccffcf5 838 PERL_SYS_TERM();
a6006777
PP
839 exit(exitstatus);
840 }
841
a6006777
PP
842Now compile:
843
5e6bcc01
GID
844 % cc -o persistent persistent.c \
845 `perl -MExtUtils::Embed -e ccopts -e ldopts`
a6006777 846
d1be9408 847Here's an example script file:
a6006777
PP
848
849 #test.pl
850 my $string = "hello";
851 foo($string);
852
853 sub foo {
854 print "foo says: @_\n";
855 }
856
857Now run:
858
859 % persistent
860 Enter file name: test.pl
861 foo says: hello
862 Enter file name: test.pl
863 already compiled Embed::test_2epl->handler
864 foo says: hello
865 Enter file name: ^C
866
d95b23b2
AB
867=head2 Execution of END blocks
868
869Traditionally END blocks have been executed at the end of the perl_run.
870This causes problems for applications that never call perl_run. Since
871perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END>
872to get the new behaviour. This also enables the running of END blocks if
bf9cdc68 873the perl_parse fails and C<perl_destruct> will return the exit value.
d95b23b2 874
a2722ac9
GA
875=head2 $0 assignments
876
877When a perl script assigns a value to $0 then the perl runtime will
878try to make this value show up as the program name reported by "ps" by
879updating the memory pointed to by the argv passed to perl_parse() and
880also calling API functions like setproctitle() where available. This
881behaviour might not be appropriate when embedding perl and can be
882disabled by assigning the value C<1> to the variable C<PL_origalen>
883before perl_parse() is called.
884
885The F<persistent.c> example above is for instance likely to segfault
886when $0 is assigned to if the C<PL_origalen = 1;> assignment is
887removed. This because perl will try to write to the read only memory
888of the C<embedding[]> strings.
889
8ebc5c01
PP
890=head2 Maintaining multiple interpreter instances
891
8a7dc658
JO
892Some rare applications will need to create more than one interpreter
893during a session. Such an application might sporadically decide to
54310121 894release any resources associated with the interpreter.
8a7dc658
JO
895
896The program must take care to ensure that this takes place I<before>
9bbedd82
JH
897the next interpreter is constructed. By default, when perl is not
898built with any special options, the global variable
9cde0e7f 899C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't
9bbedd82
JH
900usually needed when a program only ever creates a single interpreter
901in its entire lifetime.
8a7dc658 902
9cde0e7f 903Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean:
8a7dc658 904
8ebc5c01
PP
905 while(1) {
906 ...
9cde0e7f 907 /* reset global variables here with PL_perl_destruct_level = 1 */
bf9cdc68 908 PL_perl_destruct_level = 1;
54310121 909 perl_construct(my_perl);
8ebc5c01
PP
910 ...
911 /* clean and reset _everything_ during perl_destruct */
bf9cdc68 912 PL_perl_destruct_level = 1;
54310121
PP
913 perl_destruct(my_perl);
914 perl_free(my_perl);
8ebc5c01
PP
915 ...
916 /* let's go do it again! */
917 }
918
54310121 919When I<perl_destruct()> is called, the interpreter's syntax parse tree
bf9cdc68
RG
920and symbol tables are cleaned up, and global variables are reset. The
921second assignment to C<PL_perl_destruct_level> is needed because
922perl_construct resets it to C<0>.
8ebc5c01 923
8a7dc658 924Now suppose we have more than one interpreter instance running at the
9bbedd82
JH
925same time. This is feasible, but only if you used the Configure option
926C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when
bf9cdc68 927building perl. By default, enabling one of these Configure options
9bbedd82 928sets the per-interpreter global variable C<PL_perl_destruct_level> to
bf9cdc68
RG
929C<1>, so that thorough cleaning is automatic and interpreter variables
930are initialized correctly. Even if you don't intend to run two or
931more interpreters at the same time, but to run them sequentially, like
932in the above example, it is recommended to build perl with the
933C<-Dusemultiplicity> option otherwise some interpreter variables may
934not be initialized correctly between consecutive runs and your
935application may crash.
9bbedd82 936
832a833b
JH
937See also L<perlxs/Thread-aware system interfaces>.
938
9bbedd82
JH
939Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity>
940is more appropriate if you intend to run multiple interpreters
941concurrently in different threads, because it enables support for
942linking in the thread libraries of your system with the interpreter.
8ebc5c01
PP
943
944Let's give it a try:
945
946
947 #include <EXTERN.h>
8a7dc658 948 #include <perl.h>
8ebc5c01
PP
949
950 /* we're going to embed two interpreters */
8ebc5c01 951
8ebc5c01
PP
952 #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)"
953
8ebc5c01
PP
954 int main(int argc, char **argv, char **env)
955 {
1ccffcf5 956 PerlInterpreter *one_perl, *two_perl;
0301e899
Z
957 char *one_args[] = { "one_perl", SAY_HELLO, NULL };
958 char *two_args[] = { "two_perl", SAY_HELLO, NULL };
8ebc5c01 959
1ccffcf5
IZ
960 PERL_SYS_INIT3(&argc,&argv,&env);
961 one_perl = perl_alloc();
962 two_perl = perl_alloc();
963
9bbedd82 964 PERL_SET_CONTEXT(one_perl);
8ebc5c01 965 perl_construct(one_perl);
9bbedd82 966 PERL_SET_CONTEXT(two_perl);
8ebc5c01
PP
967 perl_construct(two_perl);
968
9bbedd82 969 PERL_SET_CONTEXT(one_perl);
8ebc5c01 970 perl_parse(one_perl, NULL, 3, one_args, (char **)NULL);
9bbedd82 971 PERL_SET_CONTEXT(two_perl);
8ebc5c01
PP
972 perl_parse(two_perl, NULL, 3, two_args, (char **)NULL);
973
9bbedd82 974 PERL_SET_CONTEXT(one_perl);
8ebc5c01 975 perl_run(one_perl);
9bbedd82 976 PERL_SET_CONTEXT(two_perl);
8ebc5c01
PP
977 perl_run(two_perl);
978
9bbedd82 979 PERL_SET_CONTEXT(one_perl);
8ebc5c01 980 perl_destruct(one_perl);
9bbedd82 981 PERL_SET_CONTEXT(two_perl);
8ebc5c01
PP
982 perl_destruct(two_perl);
983
9bbedd82 984 PERL_SET_CONTEXT(one_perl);
8ebc5c01 985 perl_free(one_perl);
9bbedd82 986 PERL_SET_CONTEXT(two_perl);
8ebc5c01 987 perl_free(two_perl);
1ccffcf5 988 PERL_SYS_TERM();
0301e899 989 exit(EXIT_SUCCESS);
8ebc5c01
PP
990 }
991
9bbedd82
JH
992Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize
993the global state that tracks which interpreter is the "current" one on
994the particular process or thread that may be running it. It should
995always be used if you have more than one interpreter and are making
996perl API calls on both interpreters in an interleaved fashion.
997
998PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is
999used by a thread that did not create it (using either perl_alloc(), or
1000the more esoteric perl_clone()).
8ebc5c01
PP
1001
1002Compile as usual:
1003
5e6bcc01
GID
1004 % cc -o multiplicity multiplicity.c \
1005 `perl -MExtUtils::Embed -e ccopts -e ldopts`
8ebc5c01
PP
1006
1007Run it, Run it:
1008
1009 % multiplicity
1010 Hi, I'm one_perl
1011 Hi, I'm two_perl
1012
5e6bcc01
GID
1013=head2 Using Perl modules, which themselves use C libraries, from your C
1014program
96dbc785
PP
1015
1016If you've played with the examples above and tried to embed a script
5e6bcc01
GID
1017that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++
1018library, this probably happened:
96dbc785
PP
1019
1020
1021 Can't load module Socket, dynamic loading not available in this perl.
1022 (You may need to build a new perl executable which either supports
1023 dynamic loading or has the Socket module statically linked into it.)
1024
1025
1026What's wrong?
1027
1028Your interpreter doesn't know how to communicate with these extensions
1029on its own. A little glue will help. Up until now you've been
1030calling I<perl_parse()>, handing it NULL for the second argument:
1031
1032 perl_parse(my_perl, NULL, argc, my_argv, NULL);
1033
5e6bcc01
GID
1034That's where the glue code can be inserted to create the initial contact
1035between Perl and linked C/C++ routines. Let's take a look some pieces of
1036I<perlmain.c> to see how Perl does this:
96dbc785 1037
cc7dda15 1038 static void xs_init (pTHX);
96dbc785 1039
cc7dda15
GS
1040 EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
1041 EXTERN_C void boot_Socket (pTHX_ CV* cv);
96dbc785
PP
1042
1043
1044 EXTERN_C void
cc7dda15 1045 xs_init(pTHX)
96dbc785
PP
1046 {
1047 char *file = __FILE__;
1048 /* DynaLoader is a special case */
1049 newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file);
1050 newXS("Socket::bootstrap", boot_Socket, file);
1051 }
1052
1053Simply put: for each extension linked with your Perl executable
1054(determined during its initial configuration on your
1055computer or when adding a new extension),
1056a Perl subroutine is created to incorporate the extension's
1057routines. Normally, that subroutine is named
1058I<Module::bootstrap()> and is invoked when you say I<use Module>. In
1059turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl
1060counterpart for each of the extension's XSUBs. Don't worry about this
1061part; leave that to the I<xsubpp> and extension authors. If your
1062extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()>
1063for you on the fly. In fact, if you have a working DynaLoader then there
5f05dabc 1064is rarely any need to link in any other extensions statically.
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1065
1066
1067Once you have this code, slap it into the second argument of I<perl_parse()>:
1068
1069
1070 perl_parse(my_perl, xs_init, argc, my_argv, NULL);
1071
1072
1073Then compile:
1074
8a7dc658 1075 % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts`
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1076
1077 % interp
1078 use Socket;
1079 use SomeDynamicallyLoadedModule;
1080
1081 print "Now I can use extensions!\n"'
1082
1083B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code.
1084
8a7dc658 1085 % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c
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1086 % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts`
1087 % cc -c interp.c `perl -MExtUtils::Embed -e ccopts`
8a7dc658 1088 % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts`
96dbc785 1089
4929bf7b 1090Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details.
96dbc785 1091
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1092=head2 Using embedded Perl with POSIX locales
1093
1094(See L<perllocale> for information about these.)
1095When a Perl interpreter normally starts up, it tells the system it wants
1096to use the system's default locale. This is often, but not necessarily,
1097the "C" or "POSIX" locale. Absent a S<C<"use locale">> within the perl
1098code, this mostly has no effect (but see L<perllocale/Not within the
d6ded950 1099scope of "use locale">). Also, there is not a problem if the
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1100locale you want to use in your embedded Perl is the same as the system
1101default. However, this doesn't work if you have set up and want to use
1102a locale that isn't the system default one. Starting in Perl v5.20, you
1103can tell the embedded Perl interpreter that the locale is already
1104properly set up, and to skip doing its own normal initialization. It
1105skips if the environment variable C<PERL_SKIP_LOCALE_INIT> is set (even
1106if set to 0 or C<"">). A Perl that has this capability will define the
1107C pre-processor symbol C<HAS_SKIP_LOCALE_INIT>. This allows code that
1108has to work with multiple Perl versions to do some sort of work-around
1109when confronted with an earlier Perl.
1110
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1111=head1 Hiding Perl_
1112
e1020413 1113If you completely hide the short forms of the Perl public API,
d51482e4 1114add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that
35209cc8
JH
1115for example instead of writing
1116
1117 warn("%d bottles of beer on the wall", bottlecount);
1118
1119you will have to write the explicit full form
1120
1121 Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount);
1122
96090e4f
A
1123(See L<perlguts/"Background and PERL_IMPLICIT_CONTEXT"> for the explanation
1124of the C<aTHX_>. ) Hiding the short forms is very useful for avoiding
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1125all sorts of nasty (C preprocessor or otherwise) conflicts with other
1126software packages (Perl defines about 2400 APIs with these short names,
1127take or leave few hundred, so there certainly is room for conflict.)
1128
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1129=head1 MORAL
1130
1131You can sometimes I<write faster code> in C, but
5f05dabc 1132you can always I<write code faster> in Perl. Because you can use
cb1a09d0
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1133each from the other, combine them as you wish.
1134
1135
1136=head1 AUTHOR
1137
8eabb633
JH
1138Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern
1139<F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom
e010571f
GS
1140Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya
1141Zakharevich.
cb1a09d0 1142
e010571f 1143Doug MacEachern has an article on embedding in Volume 1, Issue 4 of
4b05bc8e 1144The Perl Journal ( L<http://www.tpj.com/> ). Doug is also the developer of the
e010571f
GS
1145most widely-used Perl embedding: the mod_perl system
1146(perl.apache.org), which embeds Perl in the Apache web server.
1147Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl
1148have used this model for Oracle, Netscape and Internet Information
1149Server Perl plugins.
cb1a09d0 1150
8a7dc658
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1151=head1 COPYRIGHT
1152
e010571f 1153Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All
8a7dc658
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1154Rights Reserved.
1155
608704e1 1156This document may be distributed under the same terms as Perl itself.