Re: why build start files before core gcc pass 2 ?

[Wang Baisheng <baisheng dot wang dot cn at gmail dot com>]

In build script gcc.sh, I found a comments:

"In case the threading model is NPTL, we need a shared-capable core gcc".

Yes, shared-capable gcc will need crt*.o, because libgcc*.so will
linked with crt*.o. Accoring build script, in fact, the option
"--disable-shared" is removed when building core gcc pass 2.

So if the anwser is : To support  NPTL, we need  a cross gcc with
"--enable-shared", i.e., building libgcc_.so instead of libgcc.a.
while linking libgcc_s.so, link editor need crt*.o, so build crt*.o
before building core gcc pass 2 ?

If above is true, the question is transfered to : why need  a
shared-capable core gcc to build NPTL ?

Thanks in advance.


2013/1/17 Wang Baisheng <baisheng.wang.cn@gmail.com>:
> Dear yan and All,
>
> Before using ct-ng, I built a toolchain as the following steps:
>
> 1 build binutils;
>
> 2 bare-metal(freestanding) gcc
>
>   a configured with "--with-newlib" not to depend on glibc;
>   b configured with "--disable-shared" to build static libgcc, because
> shared libgcc will linked start files, crt*.o,  which will be built in
> glibc.
>
> 3 use the bare-meta gcc builing glibc;
>
> 4 glibc is ready, so compile the full gcc.
>
> while studying ct-ng scripts, I found ct-ng add another gcc step:
>
> after building bare-meta gcc, ct-ng install libc headers and build
> crt*.o files, then build gcc pass 2, then building glibc using gcc
> pass 2, then final gcc.
>
> What I am confused is:
>
> The crt*.o files is linked into executable and shared, so why gcc need
> these files in compiling time, why gcc need crt*.o files ?
>
> in docs "How is a toolchain constructed.txt", it said "The start files
> are a very few files that gcc needs to be able to turn on thread local
> storage (TLS) on an NPTL system." But I can not grasp it.
>
> Thanks.
>
> Regards,
> Jacky

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