embedding Perl into C for Windows

ccad has asked for the wisdom of the Perl Monks concerning the following question:

Hello PerlMonks, i want to embedd a perl interpreter into a C program. See below an example, very similar to the perl doc. Now the problem is: The C program and the perl sub are running fine under LINUX. Compiling under Windows7 works fine, too, but it crashes on start. What am i doing wrong? I used the latest Strawberry Perl und did the following: perl -MExtUtils::Embed -e ccopts -e ldopts > cp1.bat and modified this batch file by inserting gcc -o ccp2 ccp2.c (and the rest what was piped in). As i said, compiling under Windows was a breeze but on start the executable crashed.

/**********************************************
* C calls a Perl subroutine and pushes two 
* double scalars.These two scalars are modified 
* in the sub and popped.
* 7.2.2014 Frank
**********************************************/
#include <EXTERN.h>
#include <perl.h>
#include <stdio.h>

/*---------------------------------------------
* global variables
*--------------------------------------------*/
double x, y;
int    icoun;
static PerlInterpreter *my_perl; 

/*---------------------------------------------
* the C-"Assembly"routine
*--------------------------------------------*/
static void harry(double x, double y)
{
printf("in Harry vor call, x= %lf, y= %lf\n",x,y);

dSP;     
ENTER;
SAVETMPS;

PUSHMARK(SP);  

XPUSHs(sv_2mortal(newSVnv(x))); // PUSH one double "n"
XPUSHs(sv_2mortal(newSVnv(y))); // PUSH one double "n"

PUTBACK;

icoun= call_pv("points",G_ARRAY);

SPAGAIN;

y= POPn;  // POP one double "n"
x= POPn;  // POP one double "n"

printf("in Harry after call, icoun= %d, x= %lf, y= %lf\n",icoun,x,y);

PUTBACK;
FREETMPS;

LEAVE;
}

/*---------------------------------------------
* main
*--------------------------------------------*/
int main(int argc, char **argv, char **env)
{
char *my_argv[]= {"", "punkte2.pl"};

x= 3.1416;
y= 47.11;

printf("Controll of the entry values\n");
printf("X= %lf, Y= %lf\n",x,y);

/*=============================================
* start Perl Interpreter
*============================================*/
my_perl= perl_alloc();
perl_construct(my_perl);

perl_parse(my_perl,NULL, 2, my_argv, (char **)NULL);
perl_run(my_perl);

/*=============================================
* launch the C-"Assembly" routine
*============================================*/
harry(x,y);

/*=============================================
* ...and clean up
*============================================*/
perl_destruct(my_perl);
perl_free(my_perl);
}


#*********************************************
# the Subroutine points
# 7.2.2014 Frank
#*********************************************
sub points
{
my ($xup,$yup)= @_;  # value,value

print "in der Subroutine\n"; # kleiner Test

print "XUP= $xup, YUP= $yup\n";

$xup *= 3;
$yup *= 4;

return $xup, $yup;
}
[download]

Has anyone an idea? Many thanks in advance! Frank

Comment on embedding Perl into C for Windows Download Code

Replies are listed 'Best First'.
Re: embedding Perl into C for Windows by syphilis (Archbishop) on Feb 11, 2014 at 23:55 UTC
Hi, With the code you posted, I too get a crash on latest Strawberry Perl (5.18.2). By inserting a couple of debug printf() statements, I found that it crashed when perl_parse() was executed. Same for you ? However, there's a very similar example given in Strawberry Perl's perlembed (perldoc perlembed) documentation: #include <EXTERN.h> #include <perl.h> static PerlInterpreter my_perl; static void PerlPower(int a, int b) { dSP; / initialize stack pointer / ENTER; / everything created after here / SAVETMPS; / ...is a temporary variable. / PUSHMARK(SP); / remember the stack pointer / XPUSHs(sv_2mortal(newSViv(a))); / push the base onto the stack / XPUSHs(sv_2mortal(newSViv(b))); / push the exponent onto stack / PUTBACK; / make local stack pointer global / call_pv("expo", G_SCALAR); / call the function / SPAGAIN; / refresh stack pointer / / pop the return value from stack / printf ("%d to the %dth power is %d.\n", a, b, POPi); PUTBACK; FREETMPS; / free that return value / LEAVE; / ...and the XPUSHed "mortal" args./ } int main (int argc, char argv, char env) { char my_argv[] = { "", "power.pl" }; PERL_SYS_INIT3(&argc,&argv,&env); my_perl = perl_alloc(); perl_construct( my_perl ); perl_parse(my_perl, NULL, 2, my_argv, (char )NULL); PL_exit_flags \|= PERL_EXIT_DESTRUCT_END; perl_run(my_perl); PerlPower(3, 4); /* Compute 3 4 / perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM(); } [download] With the file "power.pl" that contains: `sub expo { my ($a, $b) = @_; return $a * $b; }` [download] That example works fine, for me. By working through the differences, you should be able to determine the reason(s) that one works, but the other doesn't. (I'm assuming the version provided by the Strawberry docs works for you.) Cheers, Rob	[reply] [d/l] [select]
Re^2: embedding Perl into C for Windows by ccad (Novice) on Feb 12, 2014 at 07:24 UTC
Hello Rob, this was the missing link: `PERL_SYS_INIT3(&argc,&argv,&env); PL_exit_flags \|= PERL_EXIT_DESTRUCT_END; PERL_SYS_TERM();` [download] I added these three commands - now it works! Many, many thanks - great! Greeting from Germany Frank	[reply] [d/l]
Re: embedding Perl into C for Windows by Anonymous Monk on Feb 11, 2014 at 21:23 UTC
Where does it crash? Can perl find power.pl? Looks like you don't have `PERL_SYS_INIT3(&argc,&argv,&env);` from http://perldoc.perl.org/perlembed.html#Fiddling-with-the-Perl-stack-from-your-C-program That might be responsible for not finding power.pl That example worked for me in 2011 :)	[reply] [d/l]
Re^2: embedding Perl into C for Windows by bulk88 (Priest) on Feb 12, 2014 at 01:38 UTC
Ditto on PERL_SYS_INIT3(&argc,&argv,&env);. It does nothing on no-threads Unix, but it mandatory on windows to setup process global (not interp/ithread global) data. Im not sure if it does something on ithreads unix.	[reply]
Re^3: embedding Perl into C for Windows by ccad (Novice) on Feb 12, 2014 at 07:25 UTC
Hello bulk88, this was the missing link: `PERL_SYS_INIT3(&argc,&argv,&env); PL_exit_flags \|= PERL_EXIT_DESTRUCT_END; PERL_SYS_TERM();` [download] I added these three commands - now it works! Many, many thanks - great! Greeting from Germany Frank	[reply] [d/l]
Re^2: embedding Perl into C for Windows by ccad (Novice) on Feb 12, 2014 at 07:28 UTC
Hello anonymous monk, thanks for your answer. The solution was: `PERL_SYS_INIT3(&argc,&argv,&env); PL_exit_flags \|= PERL_EXIT_DESTRUCT_END; PERL_SYS_TERM();` [download] I added these three commands - now it works! Frank	[reply] [d/l]