[PATCH] D12029: [lld] LinkDriver, lld-link: introduce shim.

[Rui Ueyama via llvm-commits]

Can't mingw just use lld-link style command line options instead of Unix
style? I'm not really excited about adding a new driver for COFF.

On Tue, Aug 18, 2015 at 9:28 AM, Martell Malone <martellmalone at gmail.com>
wrote:

> Martell's original proposal is to create a new linker driver LinkDriver,
>> move everything in COFF/Driver.{cpp,h} to that, and then add GNU ld support
>> to that. As a result we'd have a super driver which understands both GNU
>> and link.exe options/semantics
>
> That's not what the proposal was
> It was to move the current COFF driver to lib/LinkDriver.
> Then add a new gnu driver into COFF/Driver so that ELF/Driver and
> COFF/Driver could share more of the same code.
>
> The gist I sent in above however was to just add a new GNUDriver.cpp into
> COFF where they can live side by side.
>
> On Tue, Aug 18, 2015 at 1:05 AM, Rui Ueyama <ruiu at google.com> wrote:
>
>> On Tue, Aug 18, 2015 at 2:36 AM, Saleem Abdulrasool <
>> compnerd at compnerd.org> wrote:
>>
>>> On Monday, August 17, 2015, Rui Ueyama <ruiu at google.com> wrote:
>>>
>>>> On Sun, Aug 16, 2015 at 1:43 AM, Saleem Abdulrasool <
>>>> compnerd at compnerd.org> wrote:
>>>>
>>>>> compnerd added a comment.
>>>>>
>>>>> If we are fine with adding custom flags to the link command line, then
>>>>> aliases would be sufficient I think.  The idea is that you want to preserve
>>>>> the semantics of PE/COFF (which you called the semantics of Windows).  The
>>>>> difference is that the linker invocation should be similar to ld's, but
>>>>> continue to provide the current semantics.  There are a few extensions that
>>>>> are useful (which are compatible with the PE/COFF semantics), but the
>>>>> binaries that are generated by the alternate interface are meant to run on
>>>>> a Windows system, so losing the semantics of PE/COFF would be problematic.
>>>>>
>>>>> Just because the driver is written on/for unix, doesn't mean that the
>>>>> linker should provide unix semantics.  The semantics are that of PE/COFF
>>>>> because that is the target.  Its similar to how clang provides a GCC
>>>>> compatible interface which can still be used to generate a proper COFF
>>>>> object, even though ELF and COFF semantics are quite different.
>>>>>
>>>>
>>>> That's true, but in most use cases, Unix driver is used for Unix and
>>>> provides Unix semantics, and so are COFF. Probably more than 99 out of 100
>>>> linker invocations, the default semantics are used. So defining a new
>>>> driver layer for both Unix and Windows and then re-building the Unix and
>>>> Windows drivers on top of it is too much. I really want something simpler.
>>>>
>>>> There seems not necessary to create a new abstraction layer. We can
>>>> write a small Python script or something which takes Unix ld-ish command
>>>> line, translate that, and invokes lld-link with the translated options,
>>>> can't we?
>>>>
>>>
>>> As long as the script is part of the same repository, I see no
>>> difference.  It's just Python vs c++.  I'm not attached to any language,
>>> and we already need Python to build, so having that as a runtime dependency
>>> for llvm doesn't seem too big of a deal.  We should be able to document
>>> Python as a runtime dependency for lld I assume?
>>>
>>
>> They are different. IIUC, Martell's original proposal is to create a new
>> linker driver LinkDriver, move everything in COFF/Driver.{cpp,h} to that,
>> and then add GNU ld support to that. As a result we'd have a super driver
>> which understands both GNU and link.exe options/semantics. My proposal is
>> different. I don't want to add a full support for GNU ld options or
>> semantics for COFF. Instead I'd write an add-on script or something (which
>> can even live outside LLVM project) which is a wrapper for lld-link. Such
>> wrapper will never be able to be complete since not all GNU ld features are
>> supported by link.exe, but that may be able to be "good enough".
>>
>>
>>>
>>> --
>>> Saleem Abdulrasool
>>> compnerd (at) compnerd (dot) org
>>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150818/277f332f/attachment.html>