[cfe-commits] [PATCH] Add multiple prefixes to Option.

Michael Spencer bigcheesegs at gmail.com
Fri Oct 19 14:23:50 PDT 2012

On Fri, Oct 19, 2012 at 2:01 PM, Daniel Dunbar <daniel at zuster.org> wrote:
> On Fri, Oct 19, 2012 at 1:08 PM, Michael Spencer <bigcheesegs at gmail.com> wrote:
>> On Fri, Oct 19, 2012 at 12:48 PM, Daniel Dunbar <daniel at zuster.org> wrote:
>>> On Fri, Oct 19, 2012 at 12:39 PM, Michael Spencer <bigcheesegs at gmail.com> wrote:
>>>> On Fri, Oct 19, 2012 at 10:38 AM, Daniel Dunbar <daniel at zuster.org> wrote:
>>>>> Hi Michael,
>>>>> I understand what this patch does, but I don't really understand the
>>>>> motivation for it, yet.
>>>>> Why is this the "main feature" needed for sane gnu-ld and link command
>>>>> line support?
>>>>> It seems to me, that what you really need for those is a completely
>>>>> separate option parsing table. I can see how this patch could be
>>>>> useful if you wanted to accept the same options for the link.exe
>>>>> parsing just with a '/' at the front, but that doesn't seem right to
>>>>> me. It seems to me that the link.exe parsing or cl.exe parsing would
>>>>> end up using a completely separate parsing table.
>>>>> Can you explain?
>>>>>  - Daniel
>>>> The option tables would be completely separate. This is needed because
>>>> link supports both / and - prefixes for all options. gnu-ld supports -
>>>> and -- for almost all options.
>>> If the option tables are separate, can't we dramatically simplify this
>>> patch by making this a feature of the option table then? So that an
>>> option table can opt in to explicitly specifying all prefixes, and
>>> then we don't need to clutter up the Clang/GCC option table. Option
>>> tables which didn't opt-in to that would be required to supply a list
>>> of possible prefixes.
>>>  - Daniel
>> This would work if clang and gcc used only one prefix. There are 36
>> options that use both - and --, and 103 that use --.
> I think you misunderstood me, I was proposing initializing the option
> table with a special mode that says "all prefixes are defined as part
> of the option". Only the Clang/GCC table would use that.
>  - Daniel

Ah, I see. I feel this would greatly complicate the code as it would
require either two different parsing paths in OptParser, or
normalizing in the tablegen emitter.

- Michael Spencer

>> I can simplify this patch by defaulting to - via tblgen and only
>> changing those 139 options that are special.
>> - Michael Spencer
>>>> From the ld man page:
>>>> "For options whose names are multiple letters, either one dash or two
>>>> can precede the option name; for example, -trace-symbol and
>>>> --trace-symbol are equivalent. Note---there is one exception to this
>>>> rule. Multiple letter options that start with a lower case 'o' can
>>>> only be preceded by two dashes. This is to reduce confusion with the
>>>> -o option. So for example -omagic sets the output file name to magic
>>>> whereas --omagic sets the NMAGIC flag on the output."
>>>> - Michael Spencer
>>>>> On Thu, Oct 18, 2012 at 3:53 PM, Michael Spencer <bigcheesegs at gmail.com> wrote:
>>>>>> Hi ddunbar,
>>>>>> This patch adds support for multiple prefixes per option. This is the main feature needed for sane gnu-ld and link command line support.
>>>>>> Most of the ["-"]'s can be refactored to a common class in tablegen, but I have a few more widespread tablegen changes I want to make before doing all the refactoring needed.
>>>>>> http://llvm-reviews.chandlerc.com/D69
>>>>>> Files:
>>>>>>   include/clang/Driver/Arg.h
>>>>>>   include/clang/Driver/CC1AsOptions.h
>>>>>>   include/clang/Driver/CC1AsOptions.td
>>>>>>   include/clang/Driver/CC1Options.td
>>>>>>   include/clang/Driver/OptParser.td
>>>>>>   include/clang/Driver/OptTable.h
>>>>>>   include/clang/Driver/Option.h
>>>>>>   include/clang/Driver/Options.h
>>>>>>   include/clang/Driver/Options.td
>>>>>>   lib/Driver/Arg.cpp
>>>>>>   lib/Driver/ArgList.cpp
>>>>>>   lib/Driver/CC1AsOptions.cpp
>>>>>>   lib/Driver/Driver.cpp
>>>>>>   lib/Driver/DriverOptions.cpp
>>>>>>   lib/Driver/OptTable.cpp
>>>>>>   lib/Driver/Option.cpp
>>>>>>   lib/Driver/Tools.cpp
>>>>>>   lib/Frontend/CompilerInvocation.cpp
>>>>>>   utils/TableGen/OptParserEmitter.cpp

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