r348276 - [AST][NFC] Make ArrayTypeTraitExpr non polymorphic

[Bruno Ricci via cfe-commits]

On 12/12/2018 07:27, Mikael Holmén wrote:
> Hi,
> 
> On 12/11/18 5:49 PM, Bruno Ricci wrote:
>> Hi Mikael,
>>
>> I can indeed reproduce this with gcc 5.5.0 when doing a Release
>> build with assertions. I cannot reproduce this with gcc 6.5.0
>> (also with a Release build with assertions), nor can I reproduce
>> this with clang 7 (also with a Release build with assertions).
>>
>> I tried to instrument StringRefCheckerVisitor::VisitChildren but this
>> just causes the stack overflow to move to CGBuilder.
>>
>> What is stranger is that the reproducer do not even causes
>> an ArrayTypeTraitExpr node to be created.
>>
>> Increasing the maximum stack size with ulimit by a small amount fixes
>> the problem, so I don't think this is a mis-compilation either.
> 
> Oh, I didn't realize it actually passed with a larger stack, I thought 
> it recursed forever.
> 
> I see now that before the change clang-tidy compiled with gcc 5.4 passed 
> with stacksize limited to 2288k and after it needs 9372k.
> 
> If I use clang 3.6 to compile I needed 1747k before the change and 1750k 
> after.

Huh ? This is a huge increase.

> 
>>
>> I think that this change is correct since no one is using the polymorphism
>> of ArrayTypeTraitExpr. Indeed taking the blunt step of making it final do
>> not causes any failure.
>>
>> The only possible explaination I can think of is that for one reason
>> or another, with this particular compiler + build settings, this change
>> causes an increase of stack usage which exceeed the default limit ?
>>
> 
> Yes perhaps it's just some deficiency in old gcc versions that is 
> exposed by this then.
> 
> Thanks,
> Mikael

Perhaps it is just indeed a deficiency in gcc 5.4, but this is strange.

Bruno
> 
> 
>> Regards,
>> Bruno