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digitalmars.D.learn - scope attribute and catching exception

reply Paolo Invernizzi <arathorn fastwebnet.it> writes:
Hi all,
Someone can explain me why the scope attribute of r2 is not satisfied? It's a
bug or an expected behaviour?

Paolo

module tests.d.scopes.t02.test;

class Resource {
    static int allocated = 0;
    this( bool mustThrow = false ){
        allocated ++;
        if( mustThrow ) throw new Exception("bang");
    }
    ~this(){
        allocated --;
    }
}

void main(){
    
    
    // Why the destructor of r2 is not called when exiting the scope?
    {
        try {
            scope r1 = new Resource();
            scope r2 = new Resource(true);
        }
        catch(Exception e){}
    }
    //assert( Resource.allocated == 0); // Expected
    assert( Resource.allocated == 1 ); // What's happening
    
}
Oct 13 2008
next sibling parent reply "Denis Koroskin" <2korden gmail.com> writes:
On Mon, 13 Oct 2008 13:50:46 +0400, Paolo Invernizzi  
<arathorn fastwebnet.it> wrote:


 Hi all,
 Someone can explain me why the scope attribute of r2 is not satisfied?  
 It's a bug or an expected behaviour?

 Paolo

 module tests.d.scopes.t02.test;

 class Resource {
     static int allocated = 0;
     this( bool mustThrow = false ){
         allocated ++;
         if( mustThrow ) throw new Exception("bang");
     }
     ~this(){
         allocated --;
     }
 }

 void main(){
    // Why the destructor of r2 is not called when exiting the scope?
     {
         try {
             scope r1 = new Resource();
             scope r2 = new Resource(true);
         }
         catch(Exception e){}
     }
     //assert( Resource.allocated == 0); // Expected
     assert( Resource.allocated == 1 ); // What's happening
 }


Looks like no destructor is called if ctor throws an exception.
Try throwing outside of it and see what happens.
Oct 13 2008
parent Paolo Invernizzi <arathorn fastwebnet.it> writes:
Denis Koroskin Wrote:


 Looks like no destructor is called if ctor throws an exception.
 Try throwing outside of it and see what happens.


In that case everything is ok. So it's a bug?

    // In this case everything it's ok
    {
        try {
            scope r1 = new Resource();
            scope r2 = new Resource();
            throw new Exception("bang");
        }
        catch(Exception e){}
    }
    assert( Resource.allocated == 0); // Expected
Oct 13 2008
prev sibling parent reply Max Samukha <samukha voliacable.com.removethis> writes:
On Mon, 13 Oct 2008 05:50:46 -0400, Paolo Invernizzi
<arathorn fastwebnet.it> wrote:


Hi all,
Someone can explain me why the scope attribute of r2 is not satisfied? It's a
bug or an expected behaviour?

Paolo

module tests.d.scopes.t02.test;

class Resource {
    static int allocated = 0;
    this( bool mustThrow = false ){
        allocated ++;
        if( mustThrow ) throw new Exception("bang");
    }
    ~this(){
        allocated --;
    }
}

void main(){
    
    
    // Why the destructor of r2 is not called when exiting the scope?
    {
        try {
            scope r1 = new Resource();
            scope r2 = new Resource(true);
        }
        catch(Exception e){}
    }
    //assert( Resource.allocated == 0); // Expected
    assert( Resource.allocated == 1 ); // What's happening
    
}


because r2 wasn't successfully created and there is nothing to call
the destructor on:

class Resource {
    static int allocated = 0;
    this( bool mustThrow = false )
   {  
        scope(success)       
            allocated++;
        if( mustThrow ) throw new Exception("bang");
    }
    ~this(){
        allocated --;
    }
}
Oct 13 2008
parent reply Paolo Invernizzi <arathorn fastwebnet.it> writes:
Max Samukha Wrote:


 because r2 wasn't successfully created and there is nothing to call
 the destructor on:


I think is more complicated... see this:

module tests.d.scopes.t02.test;

class Resource {
    static int allocated = 0;
    this( bool mustThrow = false ){
        allocated ++;
        if( mustThrow ) throw new Exception("bang");
    }
    ~this(){
        allocated --;
    }
}
class Factory {
    Resource resource(bool b=false){
        return new Resource(b);
    }
}

import std.gc, std.stdio;
void main(){
    // In this case everything it's ok
    {
        try {
            scope r1 = new Resource(true);
            assert( false );
        }
        catch(Exception e){}
        assert( Resource.allocated == 1);
        std.gc.fullCollect();
        assert( Resource.allocated == 1 );
    }
    
    Resource.allocated = 0;
    
    // In this case the destructor IS called, only on collect...
    {
        auto f = new Factory();
        try {
            scope r1 = f.resource(true);
            assert( false );
        }
        catch(Exception e){}
        assert( Resource.allocated == 1);
        std.gc.fullCollect();
        assert( Resource.allocated == 0 ); // Dho! Destructor called!
    }
}
Oct 13 2008
parent Max Samukha <samukha voliacable.com.removethis> writes:
On Mon, 13 Oct 2008 08:03:32 -0400, Paolo Invernizzi
<arathorn fastwebnet.it> wrote:


Max Samukha Wrote:


 because r2 wasn't successfully created and there is nothing to call
 the destructor on:


I think is more complicated... see this:

module tests.d.scopes.t02.test;

class Resource {
    static int allocated = 0;
    this( bool mustThrow = false ){
        allocated ++;
        if( mustThrow ) throw new Exception("bang");
    }
    ~this(){
        allocated --;
    }
}
class Factory {
    Resource resource(bool b=false){
        return new Resource(b);
    }
}

import std.gc, std.stdio;
void main(){
    // In this case everything it's ok
    {
        try {
            scope r1 = new Resource(true);
            assert( false );
        }
        catch(Exception e){}
        assert( Resource.allocated == 1);
        std.gc.fullCollect();
        assert( Resource.allocated == 1 );
    }
    
    Resource.allocated = 0;
    
    // In this case the destructor IS called, only on collect...
    {
        auto f = new Factory();
        try {
            scope r1 = f.resource(true);
            assert( false );
        }
        catch(Exception e){}
        assert( Resource.allocated == 1);
        std.gc.fullCollect();
        assert( Resource.allocated == 0 ); // Dho! Destructor called!
    }
}


I think this is a bug.
Oct 13 2008