Messages in this thread | | | Date | Tue, 22 Mar 2022 18:25:50 +0100 | From | Willy Tarreau <> | Subject | Re: [RFC PATCH v2 2/8] tools/nolibc: Remove .global _start from the entry point code |
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Hi Nick,
On Tue, Mar 22, 2022 at 10:09:18AM -0700, Nick Desaulniers wrote: > On Tue, Mar 22, 2022 at 3:21 AM Ammar Faizi <ammarfaizi2@gnuweeb.org> wrote: > > > > Building with clang yields the following error: > > ``` > > <inline asm>:3:1: error: _start changed binding to STB_GLOBAL > > .global _start > > ^ > > 1 error generated. > > ``` > > Make sure only specify one between `.global _start` and `.weak _start`. > > Removing `.global _start`. > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > Yes, symbols should either be `.weak` or `.global`. The warning from > Clang's integrated assembler is meant to flush out funny business. > > I assume there's a good reason _why_ _start is weak and not strong?
Yes, the issue appears when you start to build programs made of more than one C file. That's why we have a few weak symbols here and there (others like errno are static and the lack of inter-unit portability is assumed).
> Then again, I'm not familiar with nolibc.
No problem. The purpose is clearly *not* to implement a libc, but to have something very lightweight that allows to compile trivial programs. A good example of this is tools/testing/selftests/rcutorture/bin/mkinitrd.sh. I'm personally using a tiny pre-init shell that I always package with my kernels and that builds with them [1]. It will never do big things but the balance between ease of use and coding effort is pretty good in my experience. And I'm also careful not to make it complicated to use nor to maintain, pragmatism is important and the effort should remain on the program developer if some arbitration is needed.
Regards, Willy
[1] https://github.com/formilux/flxutils/tree/master/init
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