[LINUX-KERNEL] C++ in linux kernel

[LINUX-KERNEL] C++ in linux kernel

[rohit h]

Hi,
 I am a kernel newbie.
 I tried to insmod a C++ module containing classes, inheritance.
 I am getting 'unresolved symbol' error when I use the 'new' keyword.
 What could the problem be?

 What kind of runtime support is needed ( arm linux kernel)? Is a
patch available for it?

 Thanks,
Rohit

Re: C++ in linux kernel

[KOSAKI Motohiro]

Hi

>  I am a kernel newbie.
>  I tried to insmod a C++ module containing classes, inheritance.
>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
>  What could the problem be?

under using gcc, new operator use malloc by default.
but linux doesn't have malloc.

Could you create custom allocater?

>  What kind of runtime support is needed ( arm linux kernel)? Is a
> patch available for it?

may be nothing.

- kosaki

Re: [LINUX-KERNEL] C++ in linux kernel

[Bernd Petrovitsch]

On Fre, 2008-02-08 at 10:51 +0530, rohit h wrote:
> Hi,
>  I am a kernel newbie.
>  I tried to insmod a C++ module containing classes, inheritance.
>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
>  What could the problem be?

That you used C++ is the problem. Use plain C and the gcc.

>  What kind of runtime support is needed ( arm linux kernel)? Is a
> patch available for it?

Google for "linux kernel c++" and read on - this has been discussed
several times on this list.

	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
mobil: +43 664 4416156                 fax: +43 1 7890849-55
          Embedded Linux Development and Services

Re: C++ in linux kernel

[Andi Kleen]

"rohit h" <hrohit85@gmail.com> writes:

> Hi,
>  I am a kernel newbie.
>  I tried to insmod a C++ module containing classes, inheritance.
>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
>  What could the problem be?

If you want to use C++ in the kernel you would need to provide
all the run time library support for it youself. It's possible,
but not easy and encouraged

-Andi

Re: [LINUX-KERNEL] C++ in linux kernel

[Joonwoo Park]

2008/2/8, rohit h <hrohit85@gmail.com>:
> Hi,
>  I am a kernel newbie.
>  I tried to insmod a C++ module containing classes, inheritance.
>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
>  What could the problem be?
>
>  What kind of runtime support is needed ( arm linux kernel)? Is a
> patch available for it?
>
>  Thanks,
> Rohit
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

Rohit,
Please take a look at click modular router which is using c++ as a
linux kernel module.
http://www.read.cs.ucla.edu/click/
The lib/glue.cc provides custom operator new.

Thanks,
Joonwoo

Re: [LINUX-KERNEL] C++ in linux kernel

[Jan Engelhardt]

On Feb 9 2008 00:14, Joonwoo Park wrote:
>2008/2/8, rohit h <hrohit85@gmail.com>:
>> Hi,
>>  I am a kernel newbie.
>>  I tried to insmod a C++ module containing classes, inheritance.
>>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
>>  What could the problem be?
>>
>>  What kind of runtime support is needed ( arm linux kernel)? Is a
>> patch available for it?
>>
>Please take a look at click modular router which is using c++ as a
>linux kernel module.
>http://www.read.cs.ucla.edu/click/
>The lib/glue.cc provides custom operator new.

Uh, let's not make the world worse :)
Just call malloc from C++, and carefully select what C++ features
you are going to use. The VMware source for example does it right.

Re: [LINUX-KERNEL] C++ in linux kernel

[Joonwoo Park]

2008/2/9, Jan Engelhardt <jengelh@computergmbh.de>:
>
> On Feb 9 2008 00:14, Joonwoo Park wrote:
> >2008/2/8, rohit h <hrohit85@gmail.com>:
> >> Hi,
> >>  I am a kernel newbie.
> >>  I tried to insmod a C++ module containing classes, inheritance.
> >>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
> >>  What could the problem be?
> >>
> >>  What kind of runtime support is needed ( arm linux kernel)? Is a
> >> patch available for it?
> >>
> >Please take a look at click modular router which is using c++ as a
> >linux kernel module.
> >http://www.read.cs.ucla.edu/click/
> >The lib/glue.cc provides custom operator new.
>
> Uh, let's not make the world worse :)
> Just call malloc from C++, and carefully select what C++ features
> you are going to use. The VMware source for example does it right.
>

Yep, also I think that if kmalloc is possible it would better than the
operator new.

Rohit,
Compiling the kernel module with g++ is not a simple work, you may
need big patch for kernel itself.
The c++ has more internal keywords than c.
e.g) new, delete, and ::
The new and delete should be re-spelled with another names.
The '::' is used in inline assembly however in c++ it means global namespace.

In conclusion, I don't recommand c++ for linux kernel without very
special goal like the click project :)

Joonwoo

Re: [LINUX-KERNEL] C++ in linux kernel

[rohit h]

On Feb 8, 2008 9:24 PM, Jan Engelhardt <jengelh@computergmbh.de> wrote:
>
> On Feb 9 2008 00:14, Joonwoo Park wrote:
> >2008/2/8, rohit h <hrohit85@gmail.com>:
> >> Hi,
> >>  I am a kernel newbie.
> >>  I tried to insmod a C++ module containing classes, inheritance.
> >>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
> >>  What could the problem be?
> >>
> >>  What kind of runtime support is needed ( arm linux kernel)? Is a
> >> patch available for it?
> >>
> >Please take a look at click modular router which is using c++ as a
> >linux kernel module.
> >http://www.read.cs.ucla.edu/click/
> >The lib/glue.cc provides custom operator new.
>
> Uh, let's not make the world worse :)
> Just call malloc from C++, and carefully select what C++ features
> you are going to use. The VMware source for example does it right.
>

>From the links given, I dig that following C++ features need runtime support:
   a. Pure virtual functions
   b. Global objects  : Needs compiler dependent changes
   c. new & delete : Can use kmalloc / kfree instead
   d. Run time type info
   e. Exceptions
I guess features d & e need considerable effort.
Apart from these, am I free to use other C++ features?
Where could I see the VMWare sources?


> Compiling the kernel module with g++ is not a simple work, you may
> need big patch for kernel itself.

I don't want to compile entire kernel.
I only want to compile my module with g++ and insmod it.
Any hint on how to write the Makefile.

Thanks in advance,
Rohit

Re: [LINUX-KERNEL] C++ in linux kernel

[vignesh babu bm]

http://www.vmware.com/download/server/open_source.html

On Feb 11, 2008 5:07 PM, rohit h <hrohit85@gmail.com> wrote:
>
> On Feb 8, 2008 9:24 PM, Jan Engelhardt <jengelh@computergmbh.de> wrote:
> >
> > On Feb 9 2008 00:14, Joonwoo Park wrote:
> > >2008/2/8, rohit h <hrohit85@gmail.com>:
> > >> Hi,
> > >>  I am a kernel newbie.
> > >>  I tried to insmod a C++ module containing classes, inheritance.
> > >>  I am getting 'unresolved symbol' error when I use the 'new' keyword.
> > >>  What could the problem be?
> > >>
> > >>  What kind of runtime support is needed ( arm linux kernel)? Is a
> > >> patch available for it?
> > >>
> > >Please take a look at click modular router which is using c++ as a
> > >linux kernel module.
> > >http://www.read.cs.ucla.edu/click/
> > >The lib/glue.cc provides custom operator new.
> >
> > Uh, let's not make the world worse :)
> > Just call malloc from C++, and carefully select what C++ features
> > you are going to use. The VMware source for example does it right.
> >
>
> From the links given, I dig that following C++ features need runtime support:
>   a. Pure virtual functions
>   b. Global objects  : Needs compiler dependent changes
>   c. new & delete : Can use kmalloc / kfree instead
>   d. Run time type info
>   e. Exceptions
> I guess features d & e need considerable effort.
> Apart from these, am I free to use other C++ features?
> Where could I see the VMWare sources?
>
>
>
> > Compiling the kernel module with g++ is not a simple work, you may
> > need big patch for kernel itself.
>
> I don't want to compile entire kernel.
> I only want to compile my module with g++ and insmod it.
> Any hint on how to write the Makefile.
>
> Thanks in advance,
> Rohit
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>



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Re: [LINUX-KERNEL] C++ in linux kernel

[Bernd Petrovitsch]

On Mon, 2008-02-11 at 17:07 +0530, rohit h wrote:
> On Feb 8, 2008 9:24 PM, Jan Engelhardt <jengelh@computergmbh.de> wrote:
[...]
> > Compiling the kernel module with g++ is not a simple work, you may
> > need big patch for kernel itself.
> 
> I don't want to compile entire kernel.
> I only want to compile my module with g++ and insmod it.
> Any hint on how to write the Makefile.

You really should learn on the differences at run-time between between
- pure C in a hosted environment (read: you have a full libc),
- pure C in a standalone environment (read: e.g. the Linux kernel), and
- C++ in both variants.

	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
mobil: +43 664 4416156                 fax: +43 1 7890849-55
          Embedded Linux Development and Services