www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - __dtor vs __xdtor

reply bitwise <bitwise.pvt gmail.com> writes:
What do they do?
What's the difference?

Thanks
Aug 11
parent reply HyperParrow <dlas nowhere.se> writes:
On Friday, 11 August 2017 at 16:53:02 UTC, bitwise wrote:
 What do they do?
 What's the difference?

 Thanks
__xdtor() also calls the __dtor() that are mixed with template mixins while __dtor() only call the __dtor() that matches to the normal ~this(){}
Aug 11
next sibling parent reply HyperParrow <dlas nowhere.se> writes:
On Friday, 11 August 2017 at 17:02:20 UTC, HyperParrow wrote:
 On Friday, 11 August 2017 at 16:53:02 UTC, bitwise wrote:
 What do they do?
 What's the difference?

 Thanks
__xdtor() also calls the __dtor() that are mixed with template mixins while __dtor() only call the __dtor() that matches to the normal ~this(){}
Nice example that speaks by itself: ================= int i; struct Foo { template ToMix(){ ~this(){++++i;}} ~this(){++i;} mixin ToMix; } void main() { Foo* foo = new Foo; foo.__xdtor; assert(i==3); Foo* other = new Foo; foo.__dtor; assert(i==4); // and not 6 ;) } =================
Aug 11
parent reply bitwise <bitwise.pvt gmail.com> writes:
On Friday, 11 August 2017 at 17:06:40 UTC, HyperParrow wrote:
[...]
 int i;
 struct Foo
 {
     template ToMix(){ ~this(){++++i;}}
     ~this(){++i;}
     mixin ToMix;
 }

 void main()
 {
     Foo* foo = new Foo;
     foo.__xdtor;
     assert(i==3);
     Foo* other = new Foo;
     foo.__dtor;
     assert(i==4); // and not 6 ;)
 }
 =================
I think you mean assert(i == 1) for the second one, right?
Aug 11
parent HyperParrow <dlas nowhere.se> writes:
On Friday, 11 August 2017 at 17:12:22 UTC, bitwise wrote:
 On Friday, 11 August 2017 at 17:06:40 UTC, HyperParrow wrote:
 [...]
 int i;
 struct Foo
 {
     template ToMix(){ ~this(){++++i;}}
     ~this(){++i;}
     mixin ToMix;
 }

 void main()
 {
     Foo* foo = new Foo;
     foo.__xdtor;
     assert(i==3);
     Foo* other = new Foo;
     foo.__dtor;
     assert(i==4); // and not 6 ;)
 }
 =================
I think you mean assert(i == 1) for the second one, right?
I made a mistake but it's not about i, which is a global. I meant "other.__dtor." just before the last assert. This doesn't change the results.
Aug 11
prev sibling parent reply bitwise <bitwise.pvt gmail.com> writes:
On Friday, 11 August 2017 at 17:02:20 UTC, HyperParrow wrote:
 On Friday, 11 August 2017 at 16:53:02 UTC, bitwise wrote:
 What do they do?
 What's the difference?

 Thanks
__xdtor() also calls the __dtor() that are mixed with template mixins while __dtor() only call the __dtor() that matches to the normal ~this(){}
Ok thanks. I don't understand why you would ever want to call __dtor then...is it possible to have only __dtor without also having __xdtor? Like, if I want to call a struct's destructor, do I have to check for both, or can I just always check for, and call __xdtor?
Aug 11
next sibling parent reply HyperParrow <dlas nowhere.se> writes:
On Friday, 11 August 2017 at 17:10:14 UTC, bitwise wrote:
 On Friday, 11 August 2017 at 17:02:20 UTC, HyperParrow wrote:
 On Friday, 11 August 2017 at 16:53:02 UTC, bitwise wrote:
 What do they do?
 What's the difference?

 Thanks
__xdtor() also calls the __dtor() that are mixed with template mixins while __dtor() only call the __dtor() that matches to the normal ~this(){}
Ok thanks. I don't understand why you would ever want to call __dtor then...
Indeed. And there's also another one for the field called __fieldDtor.
 is it possible to have only __dtor without also having __xdtor? 
 Like, if I want to call a struct's destructor, do I have to 
 check for both, or can I just always check for, and call 
 __xdtor?
Always use __xdtor unless you know there's no other destructor to call. Actually these functions are an implementation details and should be only used for low level things like custom memory handling. You can look at core/lifetime.d to see how it's used by the d runtime.
Aug 11
parent bitwise <bitwise.pvt gmail.com> writes:
On Friday, 11 August 2017 at 17:20:18 UTC, HyperParrow wrote:
 [...]
 I made a mistake but it's not about i, which is a global.
 I meant "other.__dtor." just before the last assert.
 This doesn't change the results.
hmm...indeed ;) On Friday, 11 August 2017 at 17:24:17 UTC, HyperParrow wrote:
 [...]

 is it possible to have only __dtor without also having 
 __xdtor? Like, if I want to call a struct's destructor, do I 
 have to check for both, or can I just always check for, and 
 call __xdtor?
Always use __xdtor unless you know there's no other destructor to call.
Ok cool, thanks.
Aug 11
prev sibling parent Marco Leise <Marco.Leise gmx.de> writes:
Am Fri, 11 Aug 2017 17:10:14 +0000
schrieb bitwise <bitwise.pvt gmail.com>:

 Ok thanks.
 
 I don't understand why you would ever want to call __dtor 
 then...is it possible to have only __dtor without also having 
 __xdtor? Like, if I want to call a struct's destructor, do I have 
 to check for both, or can I just always check for, and call 
 __xdtor?
I think it was simply that all the special methods needed a symbol name, so this() was called __ctor and ~this() was called __dtor. It was never supposed to cover field destruction, mixed in destructors or inheritance in classes. User code was not expected to call these directly anyways. Not very long ago __xdtor and __xpostblit were introduced that wrap up the entire finalization and copy operation. __dtor will remain as the 1:1 representation of the ~this() method. -- Marco
Aug 12