Empty section flags

[Fangrui Song <i@maskray.me>]

On Sun, Feb 9, 2020 at 9:21 PM Alan Modra <amodra@gmail.com> wrote:
>
> On Thu, Feb 06, 2020 at 05:25:33PM +0000, bd1976 llvm wrote:
> > Hi Alan, thanks for the input here. I wonder if it wouldn't be more
> > consistent to error in all cases - even in the case of different group
> > signatures. The only exception would need to be for the special section
> > names (.text, .debug_str, etc...) that the assembler has special knowledge
> > of (as you explained).
>
> Yes, let's see how that goes.
> https://sourceware.org/ml/binutils/2020-02/msg00129.html
>
> > I wonder why creating multiple sections with the
> > same name for section directives with different group signatures was
> > implemented - why not just require the use of a distinct section name for
> > these?
>
> I think plain ".text" for a group's text section is fine.  Distict
> names would just be yet another thing to track for a group.
>
> > Or, now that GNU has the ",unique,N" assembly extension (
> > https://sourceware.org/ml/binutils/2020-02/msg00028.html) that could be
> > used if the section name is fixed - it would then be explicit in the source
> > code that another section with the same name will be created.
>
> Perhaps, but we aren't designing a new toolchain.  Backwards
> compatibility can't be discarded without compelling reasons.
>
> --
> Alan Modra
> Australia Development Lab, IBM

For empty flags, should there be an error as well?

  .section .foo,"ax",@progbits; .byte 1
  .section .foo,"",@progbits; .byte 2  # no diagnostic
  .section .foo,"a",@progbits; .byte 3  # Error: changed section
attributes for .foo

Context: https://github.com/ClangBuiltLinux/linux/issues/913

I lean toward an error for consistency, and I will try making the LLVM
MC side rule stick.