From: "Sean O'Dell" <sean@...[REMOVE_THE_SPAM]>
Date: 2003-09-01T16:47:37+09:00
Subject: Re: questions about embedding ruby

Basile STARYNKEVITCH wrote:
> Dear All,
> 
> (I'm re-asking in a simpler way some previously asked questions)
> 
> I'm using ruby1.8 under Linux (Debian/sid x86); I compiled ruby1.8
> with gcc-3.3
> 
> I have the file myscript.rb
> 
> ################ file myscript.rb
> # -*- ruby -*- script myscript.rb
> def sayhello(name)
>   $stderr.printf("hello %s\n", name)
>   $stderr.flush
> end
> 
> $stderr.printf("loaded myscript.rb\n")
> $stderr.flush
> ################ end of myscript
> 
> I also have the following C program:
> 
> ################ file testemb_ruby.c
> // file testemb_ruby.c
> #include <stdio.h>
> #include <stdlib.h>
> #include <ruby.h>
> 
> int
> main (int argc, char **argv)
> {
>   VALUE res = 0;
>   int state = 0;
>   char *script = 0;
>   char *cmd = 0;
>   ruby_init ();
>   ruby_init_loadpath ();	/* to find the libraries */
>   if (argc > 1)
>     {
>       script = argv[1];
>       printf ("loading ruby script %s\n", script);
>       ruby_script (script);
>       rb_load_file (script);
>       printf ("after load_file errinfo=");
>       rb_p (ruby_errinfo);
>     }
>   if (argc > 2)
>     cmd = argv[2];
>   else
>     cmd = "sayhello(\"world\")";
>   printf ("before eval %s\n", cmd);
>   res = rb_eval_string_protect (cmd, &state);
>   printf ("after eval state=%d res=", state);
>   rb_p (res);
>   printf ("after eval errinfo=");
>   rb_p (ruby_errinfo);
>   return state;
> }				// end of main
> 
> // eof testemb_ruby.c
> ################ end of testemb_ruby.c
> 
> I'm compiling testemb_ruby.c with ruby1.8 by
> 
> cc -g -O -Wall -O -g -I /usr/local/lib/ruby/1.8/i686-linux \
>  testemb_ruby.c -o testemb_ruby -L/usr/local/lib/ruby/1.8/i686-linux \
>  -lruby_1.8-static -ldl -lcrypt -lm
> 
> I'm running it with testemb_ruby myscript.rb and I am getting
>                                       
> loading ruby script myscript.rb
> after load_file errinfo=nil
> before eval sayhello("world")
> after eval state=6 res=nil
> after eval errinfo=#<NoMethodError: (eval):9: undefined method `sayhello' for main:Object>
> 
> I have some questions:
> 
> 1. why the loading of myscript.rb don't show the "loaded myscript.rb"
>    message (without giving any errors)?
> 
> 2. why the eval of the 'sayhello("world")' fails after having loaded
>    myscript.rb which defines the sayhello function?
> 
> 3. If I run irb1.8 and type load("myscript.rb") and then
>    sayhello("world") it does work (by saying hello to me)
> 
> regards

Well, cmd is pointing to an area of the stack which no longer exists 
when the if statement returns.  Subsequent calls to printf and calls 
inside rb_eval_string_protect are probably stomping around on the 
string.  Before I looked elsewhere, I'd fix that.

Change your code to this, and try again:

int
main (int argc, char **argv)
{
   VALUE res = 0;
   int state = 0;
   char *script = 0;
   char *cmd = 0;
   char *defaultcmd = "sayhello(\"world\")";
   ruby_init ();
   ruby_init_loadpath ();	/* to find the libraries */
   if (argc > 1)
     {
       script = argv[1];
       printf ("loading ruby script %s\n", script);
       ruby_script (script);
       rb_load_file (script);
       printf ("after load_file errinfo=");
       rb_p (ruby_errinfo);
     }
   if (argc > 2)
     cmd = argv[2];
   else
     cmd = defaultcmd;
   printf ("before eval %s\n", cmd);
   res = rb_eval_string_protect (cmd, &state);
   printf ("after eval state=%d res=", state);
   rb_p (res);
   printf ("after eval errinfo=");
   rb_p (ruby_errinfo);
   return state;
}				// end of main


	Sean O'Dell