Re: Question : i386's crt0 ?

[Jeff Johnston <jjohnstn at redhat dot com>]

On 04/22/2013 03:26 PM, Julio Guerra wrote:
> Hi everyone,
>
> I am trying find out why crt0.S is not provided for i386 target as it
> is the case with, for example, powerpc's. If we consider it is
> supposed to initialize the C runtime, I don't understand why I should
> write it myself since every i386's crt0 will do the same : stack
> pointer initialization, constructor calls, etc. I really need hints
> about that, it looks like I missed something...
>
> Thank you !
>
> --
> Julio Guerra

Well, the short answer is that no one has submitted one.

The long answer is that historically, newlib started out as a C Library 
for embedded tool ports by Cygnus Solutions.  Native platforms such as 
i386 Linux were expected to use glibc with gcc supplying crt0.o.

An x86-linux port has been added for for newlib (see libc/sys/linux) if 
you are using Linux.  There is also a Cygmon port of libgloss in 
libgloss/i386.

So, you could certainly put something together from the Cygmon 
cygmon-crt0.S or use the crt0.o from gcc (which the sys/linux port uses).

For the other minimum newlib syscalls required, you can use libnosys if 
you do not have an OS.  This will create failure stubs for most things 
except for sbrk which expects you to set up a variable in your linkage 
script.  For _exit, you can cause an exception to occur (e.g. divide by 
zero).

-- Jeff J.