Embeddig ruby in a C application

ruby-talk
1

Hi folks,

I'm doing research on what are the current options to embed a ruby interpreter in an application written in C (on Windows)? About five years ago I successfully embedded MRI 1.8.7 in my app on WinXP, and I could achieve pretty cool stuff with it.

Now the same subject came up, and I was quite disappointed to find that that there seems to be no longer a definitive and proven way to do this with MRI 2.0 and up; and also every version I tried starting from 1.8.7, whether statically or dynamically linked, using either MinGW or Cygwin toolchain, and any combination of the various C embedding sample codes, it segfaults upon init on Windows 8.1.

I learned about MRuby, which seems pretty cool, and I was able to run some hello world code using it, but it's really undocumented. I was unable to do as much as get a string ruby constant's value as a C string - so communication between the two worlds needs some explanation, as well as how one can have a more complete ruby environment (standard lib, require and stuff).

Any explanation, pointers welcome!

thanks
mortee

2

are you familiar with this document?
https://github.com/ruby/ruby/blob/trunk/doc/extension.rdoc#initialize-and-start-the-interpreter

-rec/mm

···

On Fri, 2015-03-27 at 19:30 +0100, mortee wrote:

Hi folks,

I'm doing research on what are the current options to embed a ruby
interpreter in an application written in C (on Windows)? About five
years ago I successfully embedded MRI 1.8.7 in my app on WinXP, and I
could achieve pretty cool stuff with it.

Now the same subject came up, and I was quite disappointed to find that
that there seems to be no longer a definitive and proven way to do this
with MRI 2.0 and up; and also every version I tried starting from 1.8.7,
whether statically or dynamically linked, using either MinGW or Cygwin
toolchain, and any combination of the various C embedding sample codes,
it segfaults upon init on Windows 8.1.

I learned about MRuby, which seems pretty cool, and I was able to run
some hello world code using it, but it's really undocumented. I was
unable to do as much as get a string ruby constant's value as a C string
- so communication between the two worlds needs some explanation, as
well as how one can have a more complete ruby environment (standard lib,
require and stuff).

Any explanation, pointers welcome!

thanks
mortee

3

Quoting mortee (mortee.lists@kavemalna.hu):

I learned about MRuby, which seems pretty cool, and I was able to run some
hello world code using it, but it's really undocumented. I was unable to do
as much as get a string ruby constant's value as a C string - so
communication between the two worlds needs some explanation, as well as how
one can have a more complete ruby environment (standard lib, require and
stuff).

I have been developing exclusively with Mruby+C for the past four
months. With great satisfaction. It is true that there is not too much
in the field of documentation, but the code is well-written, and there
are in it more than enough practical examples to help you learn.

I do not understand precisely what you mean by "a string ruby
constant's value". You pass parameters from Ruby to C by defining
methods this way:

mrb_define_method(mrb,cls,"method_name",method_function,MRB_ARGS_REQ(1));

(in this example you specify you will pass exactly one parameter to
the method). Then, inside your method, you obtain the parameters with
a call to 'mrb_get_args.' A little bit of info can be found in the
doc/api/mruby.h.md file.

For each parameter to be received into C, one letter is included in
the second parameter to mrb_get_args. There are three ways to receive
strings (instances of String class) from Mruby to C. If you include a
'S' (capital es), you assign your string to a mrb_value (common Mruby
object). For example:

mrb_value str;
mrb_get_args(mrb,"S",&str);

Then, you handle this mrb_value with the same macros you can use in
MRI:

RSTRING_LEN(str) returns the length of the string
RSTRING_PTR(str) returns a pointer to the string's contents

If you use a lowercase 's', you will then pass to mrb_get_args two
parameters:

int str_len;
char *str;
mrb_get_args(mrb,"s",&str,&len);

str then contains the pointer to the string's data, while len contains
the length.

You can also use a lowercase 'z'. This way, the string will be
received as a 'C' (i.e. zero-terminated) string:

char *str;
mrb_get_args(mrb,"z",&str);

Just search into the Mruby code for examples of mrb_define_method and
mrb_get_args. There are many.

HTH

Carlo

···

Subject: embeddig ruby in a C application
  Date: Fri 27 Mar 15 07:30:03PM +0100

--
  * Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as che bisogno ci sarebbe
  * di parlare tanto di amore e di rettitudine? (Chuang-Tzu)

4

I've been familiar with RUBY_GLOBAL_SETUP (not needed anymore, afaik), RUBY_INIT_STACK, ruby_init(), and ruby_script().

But in actuality, if I simply load msvcrt-ruby{18|191|200}.dll, and don't even call any of those, it causes my app to segfault.

mortee

···

On 2015.03.27. 20:02, Recursive Madman wrote:

are you familiar with this document?
https://github.com/ruby/ruby/blob/trunk/doc/extension.rdoc#initialize-and-start-the-interpreter

-rec/mm

On Fri, 2015-03-27 at 19:30 +0100, mortee wrote:

Hi folks,

I'm doing research on what are the current options to embed a ruby
interpreter in an application written in C (on Windows)? About five
years ago I successfully embedded MRI 1.8.7 in my app on WinXP, and I
could achieve pretty cool stuff with it.

Now the same subject came up, and I was quite disappointed to find that
that there seems to be no longer a definitive and proven way to do this
with MRI 2.0 and up; and also every version I tried starting from 1.8.7,
whether statically or dynamically linked, using either MinGW or Cygwin
toolchain, and any combination of the various C embedding sample codes,
it segfaults upon init on Windows 8.1.

I learned about MRuby, which seems pretty cool, and I was able to run
some hello world code using it, but it's really undocumented. I was
unable to do as much as get a string ruby constant's value as a C string
- so communication between the two worlds needs some explanation, as
well as how one can have a more complete ruby environment (standard lib,
require and stuff).

Any explanation, pointers welcome!

thanks
mortee

5

Hey Carlo, thanks for the intro!

Actually, I 've been trying to make a more-than-trivial test code, e.g. acquire the value of MRUBY_DESCRIPTION from the C side, and do whatever with it. This is important for me because my application will eventually become a dll to be loaded into a host application, and I need to pass stuff back to it, so simply executing "puts MRUBY_DESCRIPTION" won't do the trick.

With MRI, I would do that by calling

StringValuePtr(rb_const_get(rb_cObject, rb_intern("MRUBY_DESCRIPTION")))

Currently, I don't really see how I'd go about that with Mruby.

mortee

···

On 2015.03.27. 20:26, Carlo E. Prelz wrote:

  Subject: embeddig ruby in a C application
  Date: Fri 27 Mar 15 07:30:03PM +0100

Quoting mortee (mortee.lists@kavemalna.hu):

I learned about MRuby, which seems pretty cool, and I was able to run some
hello world code using it, but it's really undocumented. I was unable to do
as much as get a string ruby constant's value as a C string - so
communication between the two worlds needs some explanation, as well as how
one can have a more complete ruby environment (standard lib, require and
stuff).

I have been developing exclusively with Mruby+C for the past four
months. With great satisfaction. It is true that there is not too much
in the field of documentation, but the code is well-written, and there
are in it more than enough practical examples to help you learn.

I do not understand precisely what you mean by "a string ruby
constant's value". You pass parameters from Ruby to C by defining
methods this way:

mrb_define_method(mrb,cls,"method_name",method_function,MRB_ARGS_REQ(1));

(in this example you specify you will pass exactly one parameter to
the method). Then, inside your method, you obtain the parameters with
a call to 'mrb_get_args.' A little bit of info can be found in the
doc/api/mruby.h.md file.

For each parameter to be received into C, one letter is included in
the second parameter to mrb_get_args. There are three ways to receive
strings (instances of String class) from Mruby to C. If you include a
'S' (capital es), you assign your string to a mrb_value (common Mruby
object). For example:

mrb_value str;
mrb_get_args(mrb,"S",&str);

Then, you handle this mrb_value with the same macros you can use in
MRI:

RSTRING_LEN(str) returns the length of the string
RSTRING_PTR(str) returns a pointer to the string's contents

If you use a lowercase 's', you will then pass to mrb_get_args two
parameters:

int str_len;
char *str;
mrb_get_args(mrb,"s",&str,&len);

str then contains the pointer to the string's data, while len contains
the length.

You can also use a lowercase 'z'. This way, the string will be
received as a 'C' (i.e. zero-terminated) string:

char *str;
mrb_get_args(mrb,"z",&str);

Just search into the Mruby code for examples of mrb_define_method and
mrb_get_args. There are many.

HTH

Carlo

6

OK, so any word on the current status of embedding MRI into an application on recent systems, like Win 8.1? So far any combination of MRI version and toolchain I've tried resulted in unexplained segfaults.

I'd like to explore this path too as much as possible.

thanks
mortee

···

On 2015.03.27. 20:02, Recursive Madman wrote:

are you familiar with this document?
https://github.com/ruby/ruby/blob/trunk/doc/extension.rdoc#initialize-and-start-the-interpreter

-rec/mm

On Fri, 2015-03-27 at 19:30 +0100, mortee wrote:

Hi folks,

I'm doing research on what are the current options to embed a ruby
interpreter in an application written in C (on Windows)? About five
years ago I successfully embedded MRI 1.8.7 in my app on WinXP, and I
could achieve pretty cool stuff with it.

Now the same subject came up, and I was quite disappointed to find that
that there seems to be no longer a definitive and proven way to do this
with MRI 2.0 and up; and also every version I tried starting from 1.8.7,
whether statically or dynamically linked, using either MinGW or Cygwin
toolchain, and any combination of the various C embedding sample codes,
it segfaults upon init on Windows 8.1.

I learned about MRuby, which seems pretty cool, and I was able to run
some hello world code using it, but it's really undocumented. I was
unable to do as much as get a string ruby constant's value as a C string
- so communication between the two worlds needs some explanation, as
well as how one can have a more complete ruby environment (standard lib,
require and stuff).

Any explanation, pointers welcome!

thanks
mortee

7

Quoting mortee (mortee.lists@kavemalna.hu):

Actually, I 've been trying to make a more-than-trivial test code, e.g.
acquire the value of MRUBY_DESCRIPTION from the C side, and do whatever with
it. This is important for me because my application will eventually become a
dll to be loaded into a host application, and I need to pass stuff back to
it, so simply executing "puts MRUBY_DESCRIPTION" won't do the trick.

With MRI, I would do that by calling

StringValuePtr(rb_const_get(rb_cObject, rb_intern("MRUBY_DESCRIPTION")))

Currently, I don't really see how I'd go about that with Mruby.

A quick search comes up with this example, from source file src/print.c:

  mrb_value msg;

  msg = mrb_const_get(mrb, mrb_obj_value(mrb->object_class),
                      mrb_intern_lit(mrb, "MRUBY_DESCRIPTION"));

msg is the Mruby String object. Try

printf("The string is <%s>\n",RSTRING_PTR(msg));

Carlo

···

Subject: Re: embeddig ruby in a C application
  Date: Fri 27 Mar 15 09:26:55PM +0100

--
  * Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as che bisogno ci sarebbe
  * di parlare tanto di amore e di rettitudine? (Chuang-Tzu)

8

Just as a datapoint, I have been experimenting with rubysdl & the rsdl gem. The latter is just the following C code that embeds ruby and SDL in a binary to replace `ruby` and it works fine on OSX w/ the latest clang tooling from apple:

#include <ruby.h>
#include "ruby.h"

#define HAVE_RUBY_SYSINIT 1
#define HAVE_RUBY_RUN_NODE 1
#include <SDL.h>
#include "SDL_main.h"
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#ifdef RUBY_GLOBAL_SETUP
RUBY_GLOBAL_SETUP
#endif

int main(int argc, char **argv)
{
#ifdef HAVE_LOCALE_H
  setlocale(LC_CTYPE, "");
#endif

#ifdef HAVE_RUBY_SYSINIT
  ruby_sysinit(&argc, &argv);
#endif
  {
#ifdef RUBY_INIT_STACK
    RUBY_INIT_STACK;
#endif
    ruby_init();
#ifdef HAVE_RUBY_RUN_NODE
    return ruby_run_node(ruby_options(argc, argv));
#else
    ruby_options(argc, argv);
    ruby_run(); //no return
    return 0;
#endif
  }
}

···

On Apr 2, 2015, at 11:15, mortee <mortee.lists@kavemalna.hu> wrote:

OK, so any word on the current status of embedding MRI into an application on recent systems, like Win 8.1? So far any combination of MRI version and toolchain I've tried resulted in unexplained segfaults.

I'd like to explore this path too as much as possible.

9

Okhay, so I figured out why it wasn't working.

Now I'm trying to link against libmsvcrt-ruby220-static.a using 32-bit MinGW toolchain (ruby is 32-bit too). I figured out quite a few undefined references, but I can't seem to find these:

gcc "-LC:\\Ruby221\\lib" -o ruby-embed.exe "src\\ruby-embed.o" -lmsvcrt-ruby220-static -lws2_32 -liphlpapi -limagehlp -lshlwapi -lmsvcrt
C:\Ruby221\lib/libmsvcrt-ruby220-static.a(win32.o): In function `gmtime_r':
C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/win32/win32.c:7172: undefined reference to `_imp___gmtime64_s'
C:\Ruby221\lib/libmsvcrt-ruby220-static.a(win32.o): In function `localtime_r':
C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/win32/win32.c:7196: undefined reference to `_imp___localtime64_s'
C:\Ruby221\lib/libmsvcrt-ruby220-static.a(file.o): In function `rb_file_truncate':
C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/file.c:4505: undefined reference to `ftruncate64'
C:\Ruby221\lib/libmsvcrt-ruby220-static.a(file.o): In function `rb_file_s_truncate':
C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/file.c:4446: undefined reference to `truncate64'
collect2.exe: error: ld returned 1 exit status

Any clues?

thx
mortee

···

On 2015.04.02. 21:16, Ryan Davis wrote:

On Apr 2, 2015, at 11:15, mortee <mortee.lists@kavemalna.hu> wrote:

OK, so any word on the current status of embedding MRI into an application on recent systems, like Win 8.1? So far any combination of MRI version and toolchain I've tried resulted in unexplained segfaults.

I'd like to explore this path too as much as possible.

Just as a datapoint, I have been experimenting with rubysdl & the rsdl gem. The latter is just the following C code that embeds ruby and SDL in a binary to replace `ruby` and it works fine on OSX w/ the latest clang tooling from apple:

#include <ruby.h>
#include "ruby.h"

#define HAVE_RUBY_SYSINIT 1
#define HAVE_RUBY_RUN_NODE 1
#include <SDL.h>
#include "SDL_main.h"
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#ifdef RUBY_GLOBAL_SETUP
RUBY_GLOBAL_SETUP
#endif

int main(int argc, char **argv)
{
#ifdef HAVE_LOCALE_H
   setlocale(LC_CTYPE, "");
#endif

#ifdef HAVE_RUBY_SYSINIT
   ruby_sysinit(&argc, &argv);
#endif
   {
#ifdef RUBY_INIT_STACK
     RUBY_INIT_STACK;
#endif
     ruby_init();
#ifdef HAVE_RUBY_RUN_NODE
     return ruby_run_node(ruby_options(argc, argv));
#else
     ruby_options(argc, argv);
     ruby_run(); //no return
     return 0;
#endif
   }
}

10

Ah, nice. Probably I should have been more thorough searching the source. Actually, I specifically looked for something like mrb_const_get(), but by looking over a few basic headers in there, I wouldn't find it (neither did Eclipse's code completion starting with mrb_). Anyways, it takes a bit of getting used to the other calls involved in your example, too. Thanks.

mortee

···

On 2015.03.27. 21:47, Carlo E. Prelz wrote:

  Subject: Re: embeddig ruby in a C application
  Date: Fri 27 Mar 15 09:26:55PM +0100

Quoting mortee (mortee.lists@kavemalna.hu):

Actually, I 've been trying to make a more-than-trivial test code, e.g.
acquire the value of MRUBY_DESCRIPTION from the C side, and do whatever with
it. This is important for me because my application will eventually become a
dll to be loaded into a host application, and I need to pass stuff back to
it, so simply executing "puts MRUBY_DESCRIPTION" won't do the trick.

With MRI, I would do that by calling

StringValuePtr(rb_const_get(rb_cObject, rb_intern("MRUBY_DESCRIPTION")))

Currently, I don't really see how I'd go about that with Mruby.

A quick search comes up with this example, from source file src/print.c:

   mrb_value msg;

   msg = mrb_const_get(mrb, mrb_obj_value(mrb->object_class),
                       mrb_intern_lit(mrb, "MRUBY_DESCRIPTION"));

msg is the Mruby String object. Try

printf("The string is <%s>\n",RSTRING_PTR(msg));

Carlo

11

This is nice, and works like a charm. But so far itt seems to me that Mruby can only use gems specifically targeted for it, and even those have to be specified at build time. Actually, I'd like to give more or less free hand to the users of my app with regards to the ruby code they want to execute.

So how would I go about using regular gems, especially stuff like ActiveSupport? And how can I not have to know these at build time?

thanks
mortee

···

On 2015.03.27. 21:47, Carlo E. Prelz wrote:

  Subject: Re: embeddig ruby in a C application
  Date: Fri 27 Mar 15 09:26:55PM +0100

Quoting mortee (mortee.lists@kavemalna.hu):

Actually, I 've been trying to make a more-than-trivial test code, e.g.
acquire the value of MRUBY_DESCRIPTION from the C side, and do whatever with
it. This is important for me because my application will eventually become a
dll to be loaded into a host application, and I need to pass stuff back to
it, so simply executing "puts MRUBY_DESCRIPTION" won't do the trick.

With MRI, I would do that by calling

StringValuePtr(rb_const_get(rb_cObject, rb_intern("MRUBY_DESCRIPTION")))

Currently, I don't really see how I'd go about that with Mruby.

A quick search comes up with this example, from source file src/print.c:

   mrb_value msg;

   msg = mrb_const_get(mrb, mrb_obj_value(mrb->object_class),
                       mrb_intern_lit(mrb, "MRUBY_DESCRIPTION"));

msg is the Mruby String object. Try

printf("The string is <%s>\n",RSTRING_PTR(msg));

Carlo

12

Well, one thing I can't seem to figure out. What's the Mruby equivalent of rb_protect()?

thx
mortee

···

On 2015.03.27. 21:47, Carlo E. Prelz wrote:

  Subject: Re: embeddig ruby in a C application
  Date: Fri 27 Mar 15 09:26:55PM +0100

Quoting mortee (mortee.lists@kavemalna.hu):

Actually, I 've been trying to make a more-than-trivial test code, e.g.
acquire the value of MRUBY_DESCRIPTION from the C side, and do whatever with
it. This is important for me because my application will eventually become a
dll to be loaded into a host application, and I need to pass stuff back to
it, so simply executing "puts MRUBY_DESCRIPTION" won't do the trick.

With MRI, I would do that by calling

StringValuePtr(rb_const_get(rb_cObject, rb_intern("MRUBY_DESCRIPTION")))

Currently, I don't really see how I'd go about that with Mruby.

A quick search comes up with this example, from source file src/print.c:

   mrb_value msg;

   msg = mrb_const_get(mrb, mrb_obj_value(mrb->object_class),
                       mrb_intern_lit(mrb, "MRUBY_DESCRIPTION"));

msg is the Mruby String object. Try

printf("The string is <%s>\n",RSTRING_PTR(msg));

Carlo

13

Well, OK no answer on this previous one... too bad.

My next big issue is that when I try to use MRI 2.2.1 32-bit inside a host application through a DLL, ruby_init() causes "Access violation read to 0x00000000". Is this a known phenomenon, and is there a solution for it?

thanks
mortee

···

On 2015.04.14. 13:55, mortee wrote:

Okhay, so I figured out why it wasn't working.

Now I'm trying to link against libmsvcrt-ruby220-static.a using 32-bit
MinGW toolchain (ruby is 32-bit too). I figured out quite a few
undefined references, but I can't seem to find these:

gcc "-LC:\\Ruby221\\lib" -o ruby-embed.exe "src\\ruby-embed.o"
-lmsvcrt-ruby220-static -lws2_32 -liphlpapi -limagehlp -lshlwapi -lmsvcrt

C:\Ruby221\lib/libmsvcrt-ruby220-static.a(win32.o): In function `gmtime_r':

C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/win32/win32.c:7172:

undefined reference to `_imp___gmtime64_s'

C:\Ruby221\lib/libmsvcrt-ruby220-static.a(win32.o): In function
`localtime_r':

C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/win32/win32.c:7196:

undefined reference to `_imp___localtime64_s'

C:\Ruby221\lib/libmsvcrt-ruby220-static.a(file.o): In function
`rb_file_truncate':

C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/file.c:4505:

undefined reference to `ftruncate64'

C:\Ruby221\lib/libmsvcrt-ruby220-static.a(file.o): In function
`rb_file_s_truncate':

C:\Users\Justin\Projects\rubyinstaller\sandbox\ruby22_build/../ruby_2_2/file.c:4446:

undefined reference to `truncate64'

collect2.exe: error: ld returned 1 exit status

Any clues?

thx

mortee

On 2015.04.02. 21:16, Ryan Davis wrote:

On Apr 2, 2015, at 11:15, mortee <mortee.lists@kavemalna.hu> wrote:

OK, so any word on the current status of embedding MRI into an application on recent systems, like Win 8.1? So far any combination of MRI version and toolchain I've tried resulted in unexplained segfaults.

I'd like to explore this path too as much as possible.

Just as a datapoint, I have been experimenting with rubysdl & the rsdl gem. The latter is just the following C code that embeds ruby and SDL in a binary to replace `ruby` and it works fine on OSX w/ the latest clang tooling from apple:

#include <ruby.h>

#include "ruby.h"

#define HAVE_RUBY_SYSINIT 1

#define HAVE_RUBY_RUN_NODE 1

#include <SDL.h>

#include "SDL_main.h"

#ifdef HAVE_LOCALE_H

#include <locale.h>

#endif

#ifdef RUBY_GLOBAL_SETUP

RUBY_GLOBAL_SETUP

#endif

int main(int argc, char **argv)

{

#ifdef HAVE_LOCALE_H

   setlocale(LC_CTYPE, "");

#endif

#ifdef HAVE_RUBY_SYSINIT

   ruby_sysinit(&argc, &argv);

#endif

   {

#ifdef RUBY_INIT_STACK

     RUBY_INIT_STACK;

#endif

     ruby_init();

#ifdef HAVE_RUBY_RUN_NODE

     return ruby_run_node(ruby_options(argc, argv));

#else

     ruby_options(argc, argv);

     ruby_run(); //no return

     return 0;

#endif

   }

}

14

Quoting mortee (mortee.lists@kavemalna.hu):

This is nice, and works like a charm. But so far itt seems to me that Mruby
can only use gems specifically targeted for it, and even those have to be
specified at build time. Actually, I'd like to give more or less free hand
to the users of my app with regards to the ruby code they want to execute.

So how would I go about using regular gems, especially stuff like
ActiveSupport? And how can I not have to know these at build time?

Mruby is a different beast from MRI Ruby. It is targeted to different
usage models (specifically to the embedded world), it does not plan to
substitute Ruby altogether.

The design of Mruby is surprisingly elegant. Every source tree is
self-enclosed, so that you can have as many versions coexisting on
your machine, including exactly what you need for that specific
run. The procedure is a little bit less automatic, but it gains in
flexibility.

If you need ActiveSupport, and find the mechanism of plain Ruby gems
necessary for your needs, then you'd better use MRI. Mruby certainly
offers simple gems for database access (I currently use Redis), but
feeding it with behemoth packages like those that make up the Rails
world goes (I hope) against the scope of that project.

Carlo

···

Subject: Re: embeddig ruby in a C application
  Date: gio 02 apr 15 08:19:16 +0200

--
  * Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as che bisogno ci sarebbe
  * di parlare tanto di amore e di rettitudine? (Chuang-Tzu)

15

Quoting mortee (mortee.lists@kavemalna.hu):

Well, one thing I can't seem to figure out. What's the Mruby equivalent of
rb_protect()?

I never happened to use that specific function in MRI/C. When I
recently needed to call Ruby code from C in Mruby, I passed to a C
method a block object like this:

ob.meth(arg1,arg2) do |para|
  do_something_with(para)
  do_something_else
  ...
  ...
end

and in meth I would obtain the block in mrb_get_args with something
like:

mrb_get_args(mrb,"ii&",&s->arg1,&s->arg2,&s->blk);

where arg1, arg2 and blk are defined in the C-structure associated
with the object as follows:

int arg1,arg2;
mrb_value blk;

Then, very important, to avoid the block being reaped by the GC, I
would assign it to a Ruby method variable with something like this:

mrb_funcall(mrb,self,"instance_variable_set",2,mrb_symbol_value(mrb_intern_lit(mrb,"@blk")),s->blk);
   
At that point, when I needed to execute the Ruby code (from another
C-coded method) I would call something like this:

mrb_yield(mrb,s->blk,[whatever ruby object you want to appear as 'para']);

Note that I have done this only once, and it required me quite a lot
of research and experimenting. But it nicely solves the problem I
needed to solve. YMMV

Carlo

···

Subject: Re: embeddig ruby in a C application
  Date: ven 03 apr 15 05:18:52 +0200

--
  * Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as che bisogno ci sarebbe
  * di parlare tanto di amore e di rettitudine? (Chuang-Tzu)

16

A very different beast. See Zach's talk at ruby on ales this year for some good info:

http://confreaks.tv/videos/roa2015-tba

···

On Apr 2, 2015, at 11:47, Carlo E. Prelz <fluido@fluido.as> wrote:

Mruby is a different beast from MRI Ruby. It is targeted to different
usage models (specifically to the embedded world), it does not plan to
substitute Ruby altogether.

17

Okhay, I see the point. But then what's the current, working method of running ordinary and arbitrary Ruby code inside an application?

mortee

···

On 2015.04.02. 20:47, Carlo E. Prelz wrote:

  Subject: Re: embeddig ruby in a C application
  Date: gio 02 apr 15 08:19:16 +0200

Quoting mortee (mortee.lists@kavemalna.hu):

This is nice, and works like a charm. But so far itt seems to me that Mruby
can only use gems specifically targeted for it, and even those have to be
specified at build time. Actually, I'd like to give more or less free hand
to the users of my app with regards to the ruby code they want to execute.

So how would I go about using regular gems, especially stuff like
ActiveSupport? And how can I not have to know these at build time?

Mruby is a different beast from MRI Ruby. It is targeted to different
usage models (specifically to the embedded world), it does not plan to
substitute Ruby altogether.

The design of Mruby is surprisingly elegant. Every source tree is
self-enclosed, so that you can have as many versions coexisting on
your machine, including exactly what you need for that specific
run. The procedure is a little bit less automatic, but it gains in
flexibility.

If you need ActiveSupport, and find the mechanism of plain Ruby gems
necessary for your needs, then you'd better use MRI. Mruby certainly
offers simple gems for database access (I currently use Redis), but
feeding it with behemoth packages like those that make up the Rails
world goes (I hope) against the scope of that project.

Carlo

18

I'm not entirely sure how this helps me... I need to call ruby code from C, and have some error handling/protection.

For example, after initializing mruby, I try to load a ruby file (which BTW tries to 'require' another file, which can be found on $:). I dunno what's happening, but my app fails with an assertion:

src\debug.c:135, irep->filename

I have no idea where to get a hold on this error (or, for that matter, any other error/exception I might encounter in ruby code called from C).

PS.: the mruby-require mrbgem is installed

···

On 2015.04.04. 08:52, Carlo E. Prelz wrote:

  Subject: Re: embeddig ruby in a C application
  Date: ven 03 apr 15 05:18:52 +0200

Quoting mortee (mortee.lists@kavemalna.hu):

Well, one thing I can't seem to figure out. What's the Mruby equivalent of
rb_protect()?

I never happened to use that specific function in MRI/C. When I
recently needed to call Ruby code from C in Mruby, I passed to a C
method a block object like this:

ob.meth(arg1,arg2) do |para|
   do_something_with(para)
   do_something_else
   ...
end

and in meth I would obtain the block in mrb_get_args with something
like:

mrb_get_args(mrb,"ii&",&s->arg1,&s->arg2,&s->blk);

where arg1, arg2 and blk are defined in the C-structure associated
with the object as follows:

int arg1,arg2;
mrb_value blk;

Then, very important, to avoid the block being reaped by the GC, I
would assign it to a Ruby method variable with something like this:

mrb_funcall(mrb,self,"instance_variable_set",2,mrb_symbol_value(mrb_intern_lit(mrb,"@blk")),s->blk);
    At that point, when I needed to execute the Ruby code (from another
C-coded method) I would call something like this:

mrb_yield(mrb,s->blk,[whatever ruby object you want to appear as 'para']);

Note that I have done this only once, and it required me quite a lot
of research and experimenting. But it nicely solves the problem I
needed to solve. YMMV

Carlo

19

Quoting mortee (mortee.lists@kavemalna.hu):

I'm not entirely sure how this helps me... I need to call ruby code from C,
and have some error handling/protection.

You do not specify what sort of protection you are looking for. In my
usage of mruby I generally find error messages sufficiently
informative.

For example, after initializing mruby, I try to load a ruby file (which BTW
tries to 'require' another file, which can be found on $:). I dunno what's
happening, but my app fails with an assertion:

src\debug.c:135, irep->filename

The fact that Mruby does not originally provide the 'require'
mechanism was a bit disorienting for me, but it is now
well-digested. In my mrbgem.rake files I include this line:

spec.rbfiles=(Dir.glob("#{dir}/mrblib/*.rb")+Dir.glob("#{dir}/mrblib/*/*.rb")).sort

so that all the rb files found in mrblib and included directories are
byte-compiled into the mruby executable, and do not need to be
required. Since I sort the file names I can manage the order of
inclusion by appropriately crafting their names (I prepend the name
of files that are prerequisites for others with a 2-digit number).

About your error: if you look at the debug.c file at line 135, you
will find this line:

mrb_assert(irep->filename);

Thus: whatever code you run gets at that line, and the filename member
of the mrb_irep structure pointed to by irep is null. This is why your
app fails. Why does this happen? That's up to you to find out, via
normal methods of debugging.

I have no idea where to get a hold on this error (or, for that matter, any
other error/exception I might encounter in ruby code called from C).

PS.: the mruby-require mrbgem is installed

I see that there are two, completely different, mruby-require
repositories on github. I have no experience with either, so I
cannot be of help on this, I am afraid.

Carlo

···

Subject: Re: embeddig ruby in a C application
  Date: mar 07 apr 15 06:13:11 +0200

--
  * Se la Strada e la sua Virtu' non fossero state messe da parte,
* K * Carlo E. Prelz - fluido@fluido.as che bisogno ci sarebbe
  * di parlare tanto di amore e di rettitudine? (Chuang-Tzu)