[C++-sig] Re: Boost::Python for C code -> Segmentation fault

[Mario Palomo]

thor.arne.johansen at ibas.no wrote:
> 
>>typedef struct user {
>>  char *name;
>>  int number;
>>}user;
>>
>>void greet(user *u)
>>{
>>   printf("Hello %s, your number is %d.\n"
>>          , u->name, u->number);
>>}
> 
> 
> 
> You never allocate (or initilialize) the memory for user, so your printf
> runs wild in memory.
> 
> --
> Thor Arne Johansen
> Dept. Manager R&D
> Ibas AS

But I get the "Segmentation fault" and I don't use the 'greet' function (the 
printf never get executed):

$ python
Python 2.3.4 (#2, Jul  5 2004, 09:15:05)
[GCC 3.3.4 (Debian 1:3.3.4-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>> import hello
 >>> u = hello.user()
 >>> u.number=10
Segmentation fault
$

I think Python allocate the memory for user, in the 'u' variable.


As a note, this same example works under SWIG, when I use this files:
==================> FILE: hello.c <==============
/*---------------- C code -------------------- */
#ifdef __cplusplus
extern "C" {
#endif

#include <stdio.h>

   typedef struct user {
       char *name;
         int number;
   }user;

   void greet(user *u)
   {
        printf("Hello %s, your number is %d.\n"
                      , u->name, u->number);
   }

#ifdef __cplusplus
}
#endif
/*-------------------------------------------- */


==================> FILE: hello.i <==============
%module hello
%{

typedef struct user {
   char *name;
   int number;
}user;

%}

typedef struct user {
   char *name;
   int number;
}user;

void greet(user *u);
=================================================

Using Linux (Debian Sid) 'swig' packages, when I compile, I get:
$ swig -python hello.i
$ gcc -c hello.c -Wall
$ gcc -c hello_wrap.c -Wall -I/usr/include/python2.3
$ ld -shared -o _hello.so hello.o hello_wrap.o

I get '_hello.so' and 'hello.py', that work fine:

Python 2.3.4 (#2, Jul  5 2004, 09:15:05)
[GCC 3.3.4 (Debian 1:3.3.4-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>> import hello
 >>> u = hello.user()
 >>> u.number=10
 >>> u.name="Mario"
 >>> hello.greet(u)
Hello Mario, your number is 10.
 >>>


Why this doesn't work on Boost::Python?

Thanks for your response.

Mario