malloc, DICE and IPC

[Ronald AIGNER]

Hi,

Tiago Jorge wrote:
<snip>
> 
> WOO_Send_Retval WOO_send(void){
>  CORBA_Environment env = dice_default_environment;
<snip>
> #####################################################################
> 
> all ok, until i get it to run...
> There, he gives me an error (page fault) at the stubs, when 
> unmarshalling the return value of the woo_send() call, more precisely, 
> when allocating the string(tag) inside the return structure. the line is 
> the following:
> 
> _dice_return.tag = 
> (CORBA_char_ptr)(_dice_corba_env->malloc)(_dice_tmp_offset);
> 
> i've checked the string size tha comes from the server and it is correct...
> 
> So... why is it page faulting??
That's strange. What version of dice are you using? With the above code 
it should not pagefault, but instead jump into the kernel-debugger.

Ok. You are using the default environment, which contains function 
pointers to malloc and free functions to allocate memory for such things 
as string returned from the server. These functions are (in old versions 
of dice set to NULL -> pagefault) or a default function (in the latest 
version), which jumps into the kernel debugger (to allow to see why its 
pagefaulting :).
If you turn on warnings when using dice (-Wall or see --help for other 
options) it tells you when and for which variable it uses malloc. The 
idea is, that you can provide your own versions of malloc and free (just 
have to have the same signature) and set them in the local environment:

CORBA_Environment env = dice_default_environment;
env.malloc = (dice_malloc)malloc;

The cast is to eliminate a warning: the libc malloc usually uses size_t 
type, which is not defined in L4Env.

Hope that helps,
Ron.

-- 
With regards
Ronald Aigner @ ST Microelectronics
aigner.eurecom at st.com