[llvm-dev] Handling of section vs global name conflicts

[Evgenii Stepanov via llvm-dev]

On Mon, Mar 21, 2016 at 12:29 PM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
> On 21 March 2016 at 15:07, Evgenii Stepanov <eugenis at google.com> wrote:
>> So, we emit both a global symbol for the global variable, and a local
>> symbol for the section, with the same name?
>
> We could. That is what I was expecting gas to do, but I see that both
> gas and mc produce errors.
>
> Handling this without MC is really hard. The name (in IR at least) can
> conflict with implicit sections:
>
> @".data" = global i32 42
>
> One somewhat ugly option is to just produce a cleaner error when MC
> finds the problem. With gcc one gets an error from gas.

This sounds reasonable. We need better diagnostics though. And we also
need to avoid creating such broken modules in the IR linker: imagine
module A with the section, and module B with an _internal_ global of
the same name. One way to do that is to track explicit section names
in IRLinker and force rename conflicting non-externally-visible
globals. Does it make sense?

>> This would need to be fixed both in the integrated assembler and in GAS.
>> Is it even allowed? What would the symbol references bind to, when
>> both symbols are defined?
>
> It is allowed, you can have as many symbols with the same name as you want.
>
> As for the assembly file, I would say that the section symbol should
> have a lower priority. It is always possible to refer to a section by
> putting a .Lfoo at the start of the section and referring to that.
>
> Cheers,
> Rafael