[llvm-dev] compatibility with gnu binutils

[James Henderson via llvm-dev]

On Thu, 6 Feb 2020 at 00:24, Jon Chesterfield via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> From: James Henderson via llvm-dev <llvm-dev at lists.llvm.org>
>> To: Oliver Stannard <oliver.stannard at linaro.org>
>> Cc: LLVM Dev <llvm-dev at lists.llvm.org>
>> Subject: Re: [llvm-dev] [RFC] Case insensitive assembly directives for
>>         all     targets
>>
>> +1 to all of what Oliver said. We aim for compatibility with GNU in most
>> (all?) of our other binutils, so why should the assembler be any
>> different?
>>
>
> This doesn't sound right. GNU binutils have a large quantity of legacy
> cruft, not least the redundancy between tools like readelf and objdump
> which are capable of doing the same task in exchange for different command
> line arguments.
>

> Our from-scratch binutils suite has the opportunity to be much easier to
> use than GNU's tooling. Where was this policy, which sounds like
> replicating their design mistakes bug-for-bug, agreed upon and documented?
>
Many tools (readelf, objdump, nm, objcopy etc) are used in many people's
build systems, quite often in deep configure scripts that are hard to
maintain or update for whatever reason. There have been multiple talks on
this sort of topic at various LLVM conferences (examples include  Bernhard
Rosenkränzer and Jordan Rupprecht's talks at Brussels 2019), where people
have highlighted pain points. Additionally, I have been part of or run both
BoFs (again Brussels 2019) and round tables on the topic. The overwhelming
consensus from everyone there was that people wanted compatibility with GNU
to make it easier for them to switch over to using the LLVM tools. These
discussions were written up on the mailing list (see
http://lists.llvm.org/pipermail/llvm-dev/2019-April/132032.html and
https://lists.llvm.org/pipermail/llvm-dev/2019-April/132033.html for two
recent examples). The principle is discussed on multiple reviews of changes
for the tools too.

To be clear, if there is a bug in the GNU tool, we don't try to match that.
We've also made multiple extensions and improvements over what GNU does in
some tools, some of which were also adopted in the GNU equivalent
afterwards.

Note that there are some tools (llvm-readobj, llvm-symbolizer) which are
not GNU compatible, and go their own way in output styles and command-line
processing. These both have switches and tool aliases that allow them to be
used in a GNU-like manner though too.


>
> Aside from the above query, case sensitive asm doesn't sound like a good
> feature to me either.
>
> Thanks
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