[lld] r205391 - [ELF] Add -z muldefs option.

[Shankar Easwaran]

On 4/1/2014 11:54 PM, Rui Ueyama wrote:
> On Tue, Apr 1, 2014 at 9:40 PM, Shankar Easwaran <shankare at codeaurora.org>wrote:
>
>> On 4/1/2014 11:30 PM, Rui Ueyama wrote:
>>
>>> On Tue, Apr 1, 2014 at 9:17 PM, Shankar Easwaran <shankare at codeaurora.org
>>>> wrote:
>>>   On 4/1/2014 11:12 PM, Rui Ueyama wrote:
>>>>   On Tue, Apr 1, 2014 at 8:57 PM, Shankar Easwaran <shankarke at gmail.com
>>>>>> wrote:
>>>>>>
>>>>>    Author: shankare
>>>>>
>>>>>> Date: Tue Apr  1 22:57:37 2014
>>>>>> New Revision: 205391
>>>>>>
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=205391&view=rev
>>>>>> Log:
>>>>>> [ELF] Add -z muldefs option.
>>>>>>
>>>>>> This adds -z muldefs option which is widely used over
>>>>>> --allow-multiple-definition.
>>>>>>
>>>>>> This option is supported by the GNU linker.
>>>>>>
>>>>>> Modified:
>>>>>>        lld/trunk/lib/Driver/GnuLdDriver.cpp
>>>>>>        lld/trunk/test/elf/allowduplicates.objtxt
>>>>>>
>>>>>> Modified: lld/trunk/lib/Driver/GnuLdDriver.cpp
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/Driver/
>>>>>> GnuLdDriver.cpp?rev=205391&r1=205390&r2=205391&view=diff
>>>>>>
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- lld/trunk/lib/Driver/GnuLdDriver.cpp (original)
>>>>>> +++ lld/trunk/lib/Driver/GnuLdDriver.cpp Tue Apr  1 22:57:37 2014
>>>>>> @@ -440,6 +440,16 @@ bool GnuLdDriver::parse(int argc, const
>>>>>>           groupStack.pop();
>>>>>>           break;
>>>>>>
>>>>>> +    case OPT_z: {
>>>>>> +      StringRef extOpt = inputArg->getValue();
>>>>>> +      if (extOpt == "muldefs")
>>>>>> +        ctx->setAllowDuplicates(true);
>>>>>> +      else
>>>>>> +        diagnostics << "warning: ignoring unknown argument for -z: "
>>>>>> <<
>>>>>> extOpt
>>>>>> +                    << "\n";
>>>>>> +      break;
>>>>>> +    }
>>>>>> +
>>>>>>         case OPT_INPUT:
>>>>>>         case OPT_l: {
>>>>>>           bool isDashlPrefix = (inputArg->getOption().getID() == OPT_l);
>>>>>>
>>>>>> Modified: lld/trunk/test/elf/allowduplicates.objtxt
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/
>>>>>> allowduplicates.objtxt?rev=205391&r1=205390&r2=205391&view=diff
>>>>>>
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- lld/trunk/test/elf/allowduplicates.objtxt (original)
>>>>>> +++ lld/trunk/test/elf/allowduplicates.objtxt Tue Apr  1 22:57:37 2014
>>>>>> @@ -1,8 +1,11 @@
>>>>>> -# RUN: lld -flavor gnu -target x86_64 --allow-multiple-definition -r
>>>>>> %s
>>>>>> \
>>>>>> -# RUN:     --output-filetype=yaml | FileCheck %s
>>>>>> +# RUN: lld -flavor gnu -target x86_64 --allow-multiple-definition %s \
>>>>>> +# RUN:     --output-filetype=yaml --noinhibit-exec | FileCheck %s
>>>>>>     #
>>>>>> -# RUN: not lld -flavor gnu -target x86_64 -r %s --output-filetype=yaml
>>>>>> 2>&1 \
>>>>>> -# RUN:   | FileCheck -check-prefix=ERROR %s
>>>>>> +# RUN: not lld -flavor gnu -target x86_64 %s --output-filetype=yaml \
>>>>>> +# RUN: --noinhibit-exec 2>&1 | FileCheck -check-prefix=ERROR %s
>>>>>> +#
>>>>>> +# RUN: lld -flavor gnu -target x86_64 -z muldefs %s \
>>>>>> +# RUN: --noinhibit-exec --output-filetype=yaml | FileCheck %s
>>>>>>
>>>>>>    Why do you now need --noinhibit-exec?
>>>>>>
>>>>> The testcase previously used -r, which is not supported (or) not
>>>> implemented at this time.
>>>>
>>>> --noinhibit-exec tries to keep the executable even if there is an
>>>> undefined symbol, which in this case corresponds to _start undefined.
>>>>
>>> -r was intentional -- although ELF writer does not support writing it,
>>> YAML
>>> writer does. It was slightly better than --noinhibit-exec because it did
>>> not warn on unresolved symbols unlike --noinhibit-exec.
>>>
>>>
>> You might already know, The -r option is not handled by YAML writer.
>>
>> The GnuLdDriver handles this and sets appropriate flags when -r option is
>> seen in the LinkingContext, and nothing else is done with it, since you
>> bypass the writer to the output yaml writer.
>>
>> With gnu, we consistently use --noinhibit-exec for all tests, and I would
>> prefer to stay consistent with all tests.
>
> Well, that's not true because I learned the use of -r from other test files
> having .objtxt extension in the same directory.
Ah!, Thanks for pointing that. The vast majority use noinhibit-exec though.

Below are the stats from the test/elf directory.

$find . -type f | xargs grep  -w 'noinhibit-exec' | wc -l
90
$find . -type f | xargs grep  -w '\-r' | grep lld  | wc -l
6

Not sure if it was a shortcut chosen to make sure unresolved symbols are 
accepted and not displayed to the user.

If you want to use -r back, let me know, I will not have any issues to 
go back and revert to use -r.

Thanks

Shankar Easwaran

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