mixing C/C++

mixing C/C++

[Elias Athanasopoulos]

Hello!

I want to create Ruby bindings for a C++ project, so my first
step is to call C++ code from C, since Ruby has a plain C API.

Consider I have a Foo class which its implementation is compiled
in a shared lib (libtest.so). I have a second wrapper lib:

#include "libtest.h"

extern "C" class Foo *  wrap_foo_ctor() { return new Foo(); }
extern "C" void wrap_foo_set_food(Foo *f, int i) { f->set_food(i); }
extern "C" int  wrap_foo_hello(Foo *f) { return f->hello();  }

Using the above my C program is:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
  struct Foo *m = (struct Foo*) wrap_foo_ctor();

  wrap_foo_set_food(m, 10);
  wrap_foo_hello(m);

  free(m);

  return 1;
}

And:

elathan@velka:~/src/bindings> gcc foo.c -Wall  -ltest -lwrap -o foo -L/home/elathan/src/bindings
foo.c: In function `main':
foo.c:6: warning: implicit declaration of function `wrap_foo_ctor'
foo.c:8: warning: implicit declaration of function `wrap_foo_set_food'
foo.c:9: warning: implicit declaration of function `wrap_foo_hello'
elathan@velka:~/src/bindings> ./foo
10


My main question is how to silent the implicit declaration warning in
gcc, which is, of course, correct. I want everything to compile with -Wall. 
Is there a warkaround? 

I tried to create a C header file, but I don't know how to make a C prototype
of:

 class Foo *  wrap_foo_ctor() { return new Foo(); }

Or silent the 'icompatible pointer type' warning in declarations, such as:

 int  wrap_foo_hello(Foo *f) { return f->hello();  }

TIA,
-- 
University of Athens			I bet the human brain 
Physics Department				is a kludge --Marvin Minsky 

	

Re: mixing C/C++

[James Stevenson]

Hi

this is because you program doesnt know what the functions
are called so you need to add protypes.

Either create a  header and put a prototype of the
function name in there and include the header file

or

add the prototypes to the top of the C file.

	James

On Sat, 8 Nov 2003, Elias Athanasopoulos wrote:

> Hello!
> 
> I want to create Ruby bindings for a C++ project, so my first
> step is to call C++ code from C, since Ruby has a plain C API.
> 
> Consider I have a Foo class which its implementation is compiled
> in a shared lib (libtest.so). I have a second wrapper lib:
> 
> #include "libtest.h"
> 
> extern "C" class Foo *  wrap_foo_ctor() { return new Foo(); }
> extern "C" void wrap_foo_set_food(Foo *f, int i) { f->set_food(i); }
> extern "C" int  wrap_foo_hello(Foo *f) { return f->hello();  }
> 
> Using the above my C program is:
> 
> #include <stdio.h>
> #include <stdlib.h>
> 
> int main(void)
> {
>   struct Foo *m = (struct Foo*) wrap_foo_ctor();
> 
>   wrap_foo_set_food(m, 10);
>   wrap_foo_hello(m);
> 
>   free(m);
> 
>   return 1;
> }
> 
> And:
> 
> elathan@velka:~/src/bindings> gcc foo.c -Wall  -ltest -lwrap -o foo -L/home/elathan/src/bindings
> foo.c: In function `main':
> foo.c:6: warning: implicit declaration of function `wrap_foo_ctor'
> foo.c:8: warning: implicit declaration of function `wrap_foo_set_food'
> foo.c:9: warning: implicit declaration of function `wrap_foo_hello'
> elathan@velka:~/src/bindings> ./foo
> 10
> 
> 
> My main question is how to silent the implicit declaration warning in
> gcc, which is, of course, correct. I want everything to compile with -Wall. 
> Is there a warkaround? 
> 
> I tried to create a C header file, but I don't know how to make a C prototype
> of:
> 
>  class Foo *  wrap_foo_ctor() { return new Foo(); }
> 
> Or silent the 'icompatible pointer type' warning in declarations, such as:
> 
>  int  wrap_foo_hello(Foo *f) { return f->hello();  }
> 
> TIA,
> 

Re: mixing C/C++

[Matthew Studley]

Have you considered using SWIG to automatically generate your wrappers?

... SWIG is a software development tool that connects programs written in C
and C++ with a variety of high-level programming languages. SWIG is
primarily used with common scripting languages such as Perl, Python, Tcl/Tk,
and Ruby...

http://www.swig.org/

May be a useful resource.  I've used it with C and Python.

regards

Matt

----- Original Message -----
From: Elias Athanasopoulos <elathan@phys.uoa.gr>
To: <linux-c-programming@vger.kernel.org>
Sent: Saturday, November 08, 2003 9:30 AM
Subject: mixing C/C++


> Hello!
>
> I want to create Ruby bindings for a C++ project, so my first
> step is to call C++ code from C, since Ruby has a plain C API.
>
> Consider I have a Foo class which its implementation is compiled
> in a shared lib (libtest.so). I have a second wrapper lib:
>
> #include "libtest.h"
>
> extern "C" class Foo *  wrap_foo_ctor() { return new Foo(); }
> extern "C" void wrap_foo_set_food(Foo *f, int i) { f->set_food(i); }
> extern "C" int  wrap_foo_hello(Foo *f) { return f->hello();  }
>
> Using the above my C program is:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(void)
> {
>   struct Foo *m = (struct Foo*) wrap_foo_ctor();
>
>   wrap_foo_set_food(m, 10);
>   wrap_foo_hello(m);
>
>   free(m);
>
>   return 1;
> }
>
> And:
>
> elathan@velka:~/src/bindings> gcc foo.c -Wall  -ltest -lwrap -o
foo -L/home/elathan/src/bindings
> foo.c: In function `main':
> foo.c:6: warning: implicit declaration of function `wrap_foo_ctor'
> foo.c:8: warning: implicit declaration of function `wrap_foo_set_food'
> foo.c:9: warning: implicit declaration of function `wrap_foo_hello'
> elathan@velka:~/src/bindings> ./foo
> 10
>
>
> My main question is how to silent the implicit declaration warning in
> gcc, which is, of course, correct. I want everything to compile
with -Wall.
> Is there a warkaround?
>
> I tried to create a C header file, but I don't know how to make a C
prototype
> of:
>
>  class Foo *  wrap_foo_ctor() { return new Foo(); }
>
> Or silent the 'icompatible pointer type' warning in declarations, such as:
>
>  int  wrap_foo_hello(Foo *f) { return f->hello();  }
>
> TIA,
> --
> University of Athens I bet the human brain
> Physics Department is a kludge --Marvin Minsky
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe
linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
> This incoming email to UWE has been independently scanned for viruses and
any virus detected has been removed using McAfee anti-virus software
>
>
>

Re: mixing C/C++

[Elias Athanasopoulos]

On Mon, Nov 10, 2003 at 03:00:31PM -0000, Matthew Studley wrote:
> Have you considered using SWIG to automatically generate your wrappers?
> 
> ... SWIG is a software development tool that connects programs written in C
> and C++ with a variety of high-level programming languages. SWIG is
> primarily used with common scripting languages such as Perl, Python, Tcl/Tk,
> and Ruby...

Yes, I have tried it. I found it quite complicated in the sense 
that I can't control stuff; it's difficult to hack the auto-generated
swig files. Also, it lacks compatibility with Ruby 1.8.

Thanks for your reply.

Regards,
-- 
University of Athens			I bet the human brain 
Physics Department				is a kludge --Marvin Minsky 

	

convert INT to CHAR but print's BEEP...

[J.]

Wednesday, November 12 05:19:21

Hello, I have kind of a problem with converting an int to a char.
The get_rand_str() function returns an string build of random 
charaters with a max length of int `MAX'.

This seems to work at first glance: 
~: ./program 
qqxfrd

However if I examen the output closer:
~: ./program | od -a
0000000   q   q soh   x stx   f etx   r eot   d enq  nl
0000014

Now I know why my computer keeps beeping everytime it
outputs a string :-)

What is the correct way of changing the int value to a
char value so that I can append it to the return string ?

char *get_rand_str(int max) {
 int i = 0;
 char value;
 char *retval = NULL;

 for(; i < max; i++) {
  value = get_ascii_code(97, 122);
  retval = (char *)realloc(retval, sizeof(char));
  strcat(retval, &value);
 }

 return retval;
 free(retval);
}

int get_ascii_code(int low, int high) {
 int k = 0;
 double d = 0;

 d = (double)rand() / ((double)RAND_MAX + 1);
 k = (int)(d * (high - low + 1));
 return(low + k);
}

Thank you.... 

J.

--
KonkyFong

Re: convert INT to CHAR but print's BEEP...

[Mikael Aronsson]

Hi !

The problem with strcat is that you cannot just use a pointer to the
character because all C string functions require that you end the string
with a zero (0) byte.

You could do something like this for eample:
char temp[ 2];
temp[ 0] = my_character;
temp[ 1] = '\0';
strcat( org_string, temp);

Mikael

----- Original Message ----- 
From: "J." <mailing-lists@xs4all.nl>
To: <linux-c-programming@vger.kernel.org>
Sent: Wednesday, November 12, 2003 5:35 AM
Subject: convert INT to CHAR but print's BEEP...


> Wednesday, November 12 05:19:21
>
> Hello, I have kind of a problem with converting an int to a char.
> The get_rand_str() function returns an string build of random
> charaters with a max length of int `MAX'.
>
> This seems to work at first glance:
> ~: ./program
> qqxfrd
>
> However if I examen the output closer:
> ~: ./program | od -a
> 0000000   q   q soh   x stx   f etx   r eot   d enq  nl
> 0000014
>
> Now I know why my computer keeps beeping everytime it
> outputs a string :-)
>
> What is the correct way of changing the int value to a
> char value so that I can append it to the return string ?
>
> char *get_rand_str(int max) {
>  int i = 0;
>  char value;
>  char *retval = NULL;
>
>  for(; i < max; i++) {
>   value = get_ascii_code(97, 122);
>   retval = (char *)realloc(retval, sizeof(char));
>   strcat(retval, &value);
>  }
>
>  return retval;
>  free(retval);
> }
>
> int get_ascii_code(int low, int high) {
>  int k = 0;
>  double d = 0;
>
>  d = (double)rand() / ((double)RAND_MAX + 1);
>  k = (int)(d * (high - low + 1));
>  return(low + k);
> }
>
> Thank you....
>
> J.
>
> --
> KonkyFong
>
> -
> To unsubscribe from this list: send the line "unsubscribe
linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: convert INT to CHAR - SOLVED....

[J.]

On Wed, 12 Nov 2003, Mikael Aronsson wrote:
> Hi !
> 
> The problem with strcat is that you cannot just use a pointer to the
> character because all C string functions require that you end the string
> with a zero (0) byte.
> 
> You could do something like this for eample:
> char temp[ 2];
> temp[ 0] = my_character;
> temp[ 1] = '\0';
> strcat( org_string, temp);
> 
> Mikael

THnkx.. I fixed that, and I allocated the return value with calloc, this 
works ... :)

I learnend something again....

Thnkx

J.

--
FOnkTong

Re: convert INT to CHAR but print's BEEP...

[Jeff Woods]

At 11/12/2003 05:35 AM +0100, J. wrote:
>Hello, I have kind of a problem with converting an int to a char. The 
>get_rand_str() function returns an string build of random charaters with a 
>max length of int `MAX'.

I'm sure there are faster algorithms, but how about something simple like:

#include <stdlib.h>

typedef unsigned char   U8;
typedef unsigned short  U16;

/* Set <buf_len> bytes at <buf> to random values from <low> to <high>. */
void set_rand_buf(char *buf, size_t buf_len, U8 low, U8 high) {
     U8 range = high - low + 1;
     while (buf_len--)
         *buf++ = low + (U8)((range*rand())/(RAND_MAX+1.0));
}

/* Sample calls */

#include <assert.h>

int main(void) {
     char        buf[80];
     size_t      k;

EXAMPLE_1:
     /* Completely fill buf with random data; may include embedded nulls */
     set_rand_buf(buf, sizeof buf, 0, 255);
     for (k = 0; k < sizeof buf; k++)
         printf("byte[%3d]=%3hu\n", k, (U16)buf[k]);

EXAMPLE_2:
     set_rand_buf(buf, 50, '0', '9');    /* Get 50 random ASCII digits. */
     buf[50] = 0;        /* Null-terminate the string. */
     printf("50 digits: %s\n", buf);

EXAMPLE_3:
     set_rand_buf(buf, 26, 'a', 'z');    /* Get 26 random lower-case 
letters. */
     buf[26] = 0;        /* Null-terminate the string. */
     printf("26 letters: %s\n", buf);

EXAMPLE_4:
#DEFINE LEN 27
     /* Get LEN random hex digits in ASCII */
     assert(LEN < sizeof buf);
     set_rand_buf(buf, LEN, 0, 15);      /* First get LEN hex values */
     {   /* Convert hex values from binary to ASCII */
         char *ptr = buf + LEN;
         while (ptr-- > buf)
             *ptr = (*ptr >= 10) ? ('a' - 10 + *ptr) : ('0' + *ptr);
     }
     buf[LEN] = 0;       /* Null-terminate as a string. */
     printf("hex digits %s\n", buf);


     return 0;   /* No-error program exit */
}

P.S.  The above code has never been compiled, so there may be all kinds of 
typos or other errors present.

--
Jeff Woods <kazrak+kernel@cesmail.net>