[PATCH] [ELF] Fix undefined symbol handling in DSO.

[Michael Spencer]

On Mon, Apr 7, 2014 at 1:33 PM, Rui Ueyama <ruiu at google.com> wrote:
> On Mon, Apr 7, 2014 at 1:13 PM, Shankar Easwaran <shankare at codeaurora.org>
> wrote:
>>
>> On 4/7/2014 2:53 PM, Shankar Easwaran wrote:
>>>
>>> On 4/7/2014 2:27 PM, Joerg Sonnenberger wrote:
>>>>
>>>> (2) Undefined symbols in shared libraries pulled in via -l are ignored.
>>>>>
>>>>> By "ignored", I'd think you mean "undefined symbol from library is not
>>>>> fatal", right?
>>>>
>>>> No, I really meant ignored. The most you can or should do about them is
>>>> check for consistency of the type. Otherwise they are completely
>>>> irrelevant. Trying to resolve them is just going to waste time.
>>>
>>> The undefined symbol from a shared library may most likely pull in a
>>> defined symbol from an archive library which comes later in the link line
>>> and the executable may end up exporting it.
>>>
>>> I am not sure what you meant by ignored ?
>>
>>
>> Given these oddities of choosing whether we want undefined symbols from
>> shared libraries to be picked up/not, its better that lld have a flag like
>> what it does right now.
>>
>> With this undefined symbols would only be picked up for symbol resolution,
>> if --use-shlib-undefines would be set. This would be different from Gnu but
>> I think its better to be different.
>
>
> I wouldn't think that's a good strategy. What we should do is to figure out
> what the expected behavior is, and implement the correct behavior.
> Implementing one thing in a variety of ways because we don't know which one
> is correct does not sounds like a right approach.

Agreed here. Even if the expected behavior is different than what gnu
ld does. As long as it doesn't break lots of things, we should do
what's intended.

As for this specific case, I have no idea what the correct behavior is.

- Michael Spencer

>
>> Bigcheese/Joerg ?
>>
>> Thanks
>>
>> Shankar Easwaran
>>
>>
>> --
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
>> by the Linux Foundation
>>
>