[llvm-dev] Accept --long-option but not -long-option for llvm binary utilities

[Brian Cain via llvm-dev]

Fāng-ruì,

This change has been made for llvm-objdump but not for other binutils, is that right?  Is there a plan to make all of them switch by a certain point?  It would be great for us to avoid this change spanning a release, for example.

-Brian

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Fang-ruì Sòng via llvm-dev
Sent: Sunday, April 21, 2019 1:30 AM
To: Roman Lebedev <lebedev.ri at gmail.com>
Cc: LLVM Developers Mailing List <llvm-dev at lists.llvm.org>; James Henderson <jh7370 at my.bristol.ac.uk>
Subject: [EXT] Re: [llvm-dev] Accept --long-option but not -long-option for llvm binary utilities

Did you mean --long-option (double-dash), or -long-option (single dash)?

Sorry I made a typo :(

In these GNU binutils replacements (llvm-objcopy llvm-readelf llvm-objdump ...) we have many short options that can be grouped (cl::Grouping). I meant to keep --long-option but drop -long-option. The scope of this RFC is restricted to these utilities.

In other (regular) utilities (opt llc lli llvm-as ...) we don't use grouped syntax and there is no confusion at all. People (me included) who are used to double dash options may find -long-option weird. However, changing those utilities would be too disruptive.


Single-dash variants look *very* unusual, i personally never seen them
used elsewhere.
It would be good to try to converge on double-dash variant.

Dropping support for double-dash variants instead seems rather disruptive,
especially since that will prevent usage of llvm tools as drop-in
replacement for GNU tools.

> (people sometimes call them LLVM binary utilities): llvm-objcopy (D60439), llvm-ar, llvm-size, llvm-nm, etc. llvm-objdump (not sure what to do with mach-o specific dump options), llvm-readelf (not sure what to do with llvm-readobj)
>
> On Sat, Apr 20, 2019 at 2:13 AM Reid Kleckner <rnk at google.com<mailto:rnk at google.com>> wrote:
>>
>> Are you proposing to make this the new style across all LLVM utilities? That seems needlessly disruptive. There are plenty of scripts that call `opt` and `llc` directly with single dash long options, regardless of how much we claim that they are not public facing, and are only developer tools.
>>
>> If you want to add a flag to ParseCommandLineOptions so that individual LLVM tools can opt into the new behavior gradually, I think that would be reasonable.
>>
>> On Mon, Apr 15, 2019 at 11:41 PM Fāng-ruì Sòng via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
>>>
>>> Many llvm utilities use cl::ParseCommandLineOptions() (include/Support/CommandLine.h) to parse command line options. The cl library accepts both -long-option and --long-option forms, with the single dash form (-long-option) being more popular.
>>>
>>> We also have many binary utilities (llvm-objcopy llvm-objdump llvm-readobj llvm-size ...) whose names reflect what they imitate. For compatibility with GNU binutils (and some Unix utilities transitively), these utilities accept many short options. People who use llvm utilities as replacement of GNU binutils may use the grouped option syntax (POSIX Utility Conventions), e.g. -Sx => -S -x, -Wd => -W -d, -sj.text => -s -j.text
>>>
>>> The problem is, grouped short options don't play well with -long-option. Sometimes there can be ambiguity. The issue is more prominent if the short option accepts an argument.
>>>
>>> An approach to prevent the ambiguity is to just disallow -long-option.
>>> In D60439, I plan to make llvm-objcopy accept --long-option but not -long-option.
>>> It will make its command line option parsing behave more like GNU objcopy and less like a regular llvm utility. What do people think of the divergence?
>>>
>>> Further, can we make similar changes to other llvm binary utilities (their names give people the expectation), especially those with many short options such as llvm-objdump and llvm-readobj? llvm-readobj behaves like GNU readelf if you name it "llvm-readelf". (I don't suggest disallowing -long-option for utilities other than binutils)
>>>
>>> (Note, llvm-objcopy is a new member of the family and it uses tablegen based include/llvm/Option/Opton.h, instead of cl:: as other utilities do.)
>>>
>>>
>>>
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>
>
>
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Roman


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