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发信人: boom (www), 信区: Linux
标  题: another way for C++ in kernel
发信站: BBS 水木清华站 (Sat Nov 18 13:23:56 2000)

前面的文章里面介绍过可以在kernel中用c++,但是需要崇写new,delete等等
最近由人在rtlinux的mailing list 上又提出了一种方法

(rtlinux)
On Fri, 17 Nov 2000, Alexander Lichius wrote:
＞ i tried to use c++ because i wanted to estimate the performance of
＞ plain C code and some C++ "object oriented" code. but my humble trials
＞ were killed at compile time. i think the macros for using module
＞ parameters are not defined in the g++ standard include files and i
＞ didn't have the time to track down the definition in the C includes.

Hi Alexander and Jef,
I think they are defined in linux/module.h

I have tried to compile a module in C++, but some of the necessary
kernel module #include files use C++ reserved words as variable names.
e.g., there is a variable called "new" (it is C, not C++, so it is ok)

therefore, I could not compile C++ directly, but I did this way
(skeleton code, missing many details):

file module_main_file.c (C, not C++, gcc, not g++)
#define MODULE
#define __KERNEL__
#define __RT__
..
#include <rtl_sched.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/version.h>
#include "wrapper.c"
..
int init_module() {
...my rt stuff initilization, etc...
pthread_create (&mytask, NULL, execute_module, (void *) 1);
pthread_make_periodic_np (mytask, now + 0.5 * NSECS_PER_SEC, 0.1 *
NSECS_PER_SEC);

wrapper_init();
}

void* execute_module(void *data){
  while(1){
wrapper_do();
pthread_wait_np();
  }
}

void cleanup_module() {
  wrapper_close();
  pthread_delete_np (mytask);
}

----------------end of file

file wrapper.cc

MYMAINOBJECT myobj;

void wrapper_init() { myobj.init(); }
void wrapper_do() { myobj.do(); }
void wrapper_close() { myobj.close(); }

this file I can compile with g++, and link with my c++ .o files.
then I link this .o file with the main module .o file and... voilla! my
c++ code works!

Interesting: I use rtlinux 2.0, but with rtlinux 0.6 and linux
2.0.33 I do not need this stuff: the main module can call my object and be
compiledwith g++, no problem.

＞ so i didn't bother about C++ but wrote my tasks in C.
＞ did you or anybody else compiled some working C++ kernel modules?

I know C++ is not supported in the kernel, and many people do not like
to hear "c++ and kernel", but c++ can be still worth...

-----------------------------------------------------------
Luiz Gustavo Bizarro Mirisola
Mestrando em Ciencia da Computacao - IC-Unicamp/LRV-IA-CTI
MSc Student in Computer Science
State University of Campinas, Brazil
mirisola@dcc.unicamp.br
-----------------------------------------------------------

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