Re: *ping*^2 – PR C++/88114 - PATCH for destructor not generated for "virtual ~destructor() = default"

[Tobias Burnus <burnus@net-b.de>]

On the 25th November 2018, schrieb Tobias Burnus wrote:

> On 21 November 2018, Tobias Burnus wrote:
>> Hello all,
>>
>> if a class contains any 'virtual ... = 0', it's an abstract class and 
>> for an
>> abstract class, the destructor not added to the vtable.
>>
>> For a normal
>>    virtual ~class() { }
>> that's not a problem as the class::~class() destructor will be 
>> generated during
>> the parsing of the function.
>>
>> But for
>>    virtual ~class() = default;
>> the destructor will be generated via mark_used via the vtable.
>>
>>
>> If one now declares a derived class and uses it, the class::~class() 
>> is generated
>> in that translation unit.  Unless, #pragma interface/implementation 
>> is used.
>>
>> In that case, the 'default' destructor will never be generated.
>>
>>
>> The following code seems to work both for the big code and for the 
>> example;
>> without '#pragma implementation', the destructor is not generated for 
>> the example,
>> only with.
>>
>> The patch survived boostrapping GCC with default languages on 
>> x86-64-gnu-linux
>> and "make check-g++".*
>>
>> [One probably could get rid of some of the conditions for generating 
>> the code,
>> e.g. TREE_USED and DECL_DEFAULTED_FN are probably not both needed; 
>> one might
>> want to set some additional DECL to the fn decl.]
>>
>> Does the patch and the test case make sense? Or is something else/in 
>> addition
>> needed?
>>
>> Tobias
>>
>>
>> *I do get the following failures on this CentOS6 system:
>>
>> FAIL: g++.dg/pr83239.C  -std=gnu++98 (test for excess errors)
>> Excess errors:
>> cc1plus: warning: 'void* __builtin_memset(void*, int, long unsigned 
>> int)' specified size 18446744073709551608 exceeds maximum object size 
>> 9223372036854775807 [-Wstringop-overflow=]
>> cc1plus: warning: 'void* __builtin_memset(void*, int, long unsigned 
>> int)' specified size 18446744073709551600 exceeds maximum object size 
>> 9223372036854775807 [-Wstringop-overflow=]
>>
>> FAIL: g++.dg/tls/thread_local-order2.C  -std=c++14 execution test
>> FAIL: g++.dg/tls/thread_local-order2.C  -std=c++17 execution test
>>
>> plus each 32 times:
>> FAIL: guality/guality.h: 0 PASS, 1 FAIL, 0 UNRESOLVED
>> FAIL: guality/guality.h: varl is -1, not 6