OSDev.org

Firstly, I would like to say hi to everyone here, and introduce myself.
Secondly, I would like to say that I have done a lot of research before posting here.
I've read the http://www.mega-tokyo.com/os/, searched www.google.co.uk, read most of this forum, and found many usefully links for OS dev.

I have spent the past month implementing a simple C kernel with simple video and keyboard support, using grub as boot loader.

However, I couldn't find much on how to actually implement c++ runtime support at kernel level. I don't want to debate the whole C vs C++ thing, I want to use C++ because I prefer the OO methodology, and believe an OS could be nicely encapsulated into objects.

Am I correct in assuming you can write the C++ Runtime libraries with your OS specific implementation, then link them to gcc (with c++ support), and then compile c++ source into a flat binary file which could be jumped to in PMode?
Can anyone provide a link or two to a c++ runtime library specification? or source (yeah-right)?

I understand that a lot of work needs to be done to provide the C++ support code, but I would like some ideas on how to actually go about this.
Just to clarify, I will only be using C++ for the kernel and user programs, Support code will be coded in C and ASM where applicable.

I'm not looking to write a highly efficient usable operating system, I'm just one programmer looking for a challenge

thanx for your time

I like C++ better too, and after I get a keyboard IRQ working i'm at the same prob you have....

a.f.a.i.k. the C++ runtime library is compiler-specific (even 2 different versions of GCC are not compatible about this ... so the best you can do is to link statically your kernel.o file with libg++.a included with your compiler (or some other runtime library if you're not using GCC

ok, I'm using DJGPP 2.03 on Windows XP. I couldn't find libg++.a but from reading the manual, I believe that is the UNIX name for libgpp.a. But I couldn't find that library either. I tried searching the web, but found very few useful hits, could anyone point me in the correct direction?

I've compiled and tested my mini c++ kernel on bochs 1.4.1, and everything works except for the calling of my global objects ctors and dtors, obviously.

I read on the web that I should look in crt0.c to see how my compiler implements this, but I couldn't find the source file for djgpp's crt0.c. Is this source available on-line? I tried the djgpp web site, but couldn't find any info about it there.

to compile my kernel I'm using and then using ld to link my asm code which calls my kernel main.

According to C++ Programming language third edition,

Except for the new, delete, typeid, dynamic_cast, and throw operators and the try-block, individual C++ expressions and statements need no run-time support

Are these the only off-limit parts of C++ for the kernel until support code is added?

thanks in advance.

Static (global) constructors and destructors are another area. Static constructors get called by the startup code in a compiler-specific way (check the libc source code), and destructors usually get called via atexit.

Would anyone be interested in some tutorials on writing a simple c++ kernel?

If there is some interest, I'll happily write some.

my C Kernel works with a C++ Compiler (I think)
You can test with that

I would like to see a C++ kernel tutorial. thanks.

Hi,
I did like to see a tutorial on writing a C++ kernel!

If you want to see a C++ tutorial, write one! That's why I wrote my own tutorials.

I might write a C++ one eventually, but don't hold your breath (I don't have a lot of time for OS dev at the moment).

ok, I'm going to write one.

I've got my simple c++ kernel working with a simple output stream, and just this very second got my support code to call global/static ctors and dtors...

FritzOS in pk0.7 (out this week, I hope ) will have some simple C++ stuff in it.

Does anyone know if the .ctors and .dtors sections are compiler specific to gcc?

I've used them to create a list of all the global / static objects in my linker script, and added my own __main and __atexit to walk the list calling the ctors / dotrs, without linking to any other library (libg++.a etc)

I just wanted to know how portable this solution is?

It works perfectly for me. I've also got my own versions of std::cout working, and std::cin is very close to working, just ironing out polling the keyboard and inserting chars into the stream.

whyme_t wrote:I just wanted to know how portable this solution is?

Not at all portable . In fact, not all versions of gcc are the same -- Cygwin gcc doesn't use .ctor or .dtor sections.

ah. ok.

How about this for an idea.

I assume that any given C++ compiler will use it's own way to mangle the names, and that it will do so uniformly.

Having looked at the disassembled object code for a compiled c++ program, it appears there is a way to identify which of the names refer to ctors, and which refer to dtors, of all global / static objects.

e.g __ZNSt7OStreamD1Ev is the mangled name of one of my global objects OStream. The constructor is the same except a C instead of a D.

Is there any reason why a C program couldn't be written to parse the object files, looking for the ctors and dtors, and either add .ctor .dtor sections, or add a ctor_list and dtor_list to the .data section? (assuming you told the program the mangled prefix to search for?)

and lastly, if this were possible, would this then be portable?