r205261 - DebugInfo compression: Enable compression before any sections are created.

[David Blaikie]

On Mon, Mar 31, 2014 at 4:51 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Mon, Mar 31, 2014 at 4:35 PM, Eric Christopher <echristo at gmail.com> wrote:
>> On Mon, Mar 31, 2014 at 4:13 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>> Author: dblaikie
>>> Date: Mon Mar 31 18:13:30 2014
>>> New Revision: 205261
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=205261&view=rev
>>> Log:
>>> DebugInfo compression: Enable compression before any sections are created.
>>>
>>> For those playing at home this produced some fairly subtle behavior. The
>>> sections created in InitMCObjectFileInfo were created without compressed
>>> debug info (a mistake, but not necessarily /broken). Since these
>>> sections were almost always referenced by the existing MCSection object,
>>> this almost worked.
>>>
>>> This got weird when we got to handling the relocations for a section.
>>> See ELFObjectWriter::WriteSection where we compute the true section for
>>> a relocation section by simply stripping the ".rela" prefix and then
>>> looking up that section - doing so hit the compression codepath, looked
>>> up .zdebug_blah and found a newly constructed empty section... thus,
>>> things got weird.
>>>
>>> This is untestable without a cross-project test (let me know if people
>>> would prefer that to no testing).
>>
>> *blink* Wow.
>>
>> I think the only way to do this is via projects/test-suite and ... I
>> think I'm ok not, but ick.
>
> Yeah, fair point. It'd be nice if we just had a sanctioned bucket of
> cross-project tests that didn't involve quite so many layers of crufty
> execution garbage as the test-suite...
>
>>
>>> +  if (Opts.CompressDebugSections)
>>> +    MAI->setCompressDebugSections(true);
>>>
>>
>> Please comment why on earth this has to be here, otherwise someone
>> might try to move it.
>
> Comment added in r205265.

Oops, wrong revision. r205267 is the right one.

- David