*PING*^3 [C++ Patch] – PR C++/88114 - PATCH for destructor not generated for "virtual ~destructor() = default"

[Tobias Burnus <tobias.burnus@physik.fu-berlin.de>]

On Wed, Nov 28, 2018 at 09:35:53PM +0100, Tobias Burnus wrote:
> 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