[PATCH] D45244: Add missing vtable anchors

[weiming zhao via llvm-commits]

There are tons of “weak vtable” issues found by enabling the -Wweak-vtables.
I only fixed small part of them https://reviews.llvm.org/D45893 <https://reviews.llvm.org/D45893> It’s very tedious :(

Should we enable the warning and let code owners to address them?



> On Apr 16, 2018, at 3:57 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> Hmm - yeah, I'm not sure what the criteria would be for mixing rtti/no-rtti, etc.
> 
> On Sun, Apr 15, 2018 at 8:45 PM weiming zhao <wmzhao.code at gmail.com <mailto:wmzhao.code at gmail.com>> wrote:
> It’s very similar to the issue described in http://lists.llvm.org/pipermail/llvm-dev/2016-February/095671.html <http://lists.llvm.org/pipermail/llvm-dev/2016-February/095671.html>
> My code has RTTI and LLVM doesn’t. During static linking, it hits the “undefined type info” error. After I put the anchors, the issues are solved. My guess the weak vtable and the mixed RTTI/no-RTTI confused the linker somehow. I don’t know the exact reason though.
> 
> 
>> On Apr 15, 2018, at 7:55 PM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote:
>> 
>> 
>> 
>> On Sat, Apr 14, 2018 at 10:33 PM Weiming Zhao via Phabricator <reviews at reviews.llvm.org <mailto:reviews at reviews.llvm.org>> wrote:
>> weimingz added a comment.
>> 
>> In https://reviews.llvm.org/D45244#1064905 <https://reviews.llvm.org/D45244#1064905>, @dblaikie wrote:
>> 
>> > Great - thanks for sticking with it, sorry for my dodgy explanations!
>> >
>> > If you're adding in anchors, are you using -Wweak-vtables to find them? If you're pushing through to make LLVM (& hopefully Clang/other LLVM subprojects) -Wweak-vtables clean, perhaps you can turn on the warning in the CMake config once it's clean so we don't regress this again? (it'd also be interesting to do some kind of analysis to see whether avoiding weak vtables is /actually/ worthwhile - like maybe making a temporary/local/non-committed change to change all the explicit anchors into inline functions (unanchoring them) & see if builds are much larger or longer, etc)
>> 
>> 
>> I got linker error when my code tries to statically link against some LLVM libs (like libLLVMOrc). It's a good idea to turn on -Wweak-vtables to check if we miss other cases. I will try it. Thanks
>> 
>> Hmm, I'm confused - you mean without these changes you were getting link errors due to vtable symbols for types with weak vtables? I'm not sure why that would be - your code should've been built with its own weak vtable, in that situation.
>> 
>> - Dave
>>  
>> 
>> 
>> Repository:
>>   rL LLVM
>> 
>> https://reviews.llvm.org/D45244 <https://reviews.llvm.org/D45244>

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