function to delete a class (resolved)
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This application has several pointers to be deleted in the destructor. Each is logged when created and again when deleted to reduce the possibility of an undetected memory leak. As there are several, a function is needed to do the deletes. The goal is to avoid writing all that logging code multiple times. Below is the concept. The first time it was tried the subject was an instance of a class with its own destructor. A breakpoint was placed in that destructor.
Void Delete_Stuff( WCHAR * name, void * item )
{
If( item != NULL )
{
Write_Log_Entry( L”Preparing to delete <name> at address <*item>”); // please see note
delete ( item ); // does not call the destructor
delete ( *item ); // illegal indirection
}
}EDIT: I wrote the text up in MS word and did not notice that the leading character of "delete" had been capitalized. Apologies for that. Note: An swprintf_s(…) is used to build the string and the named function does the logging. Please accept the gross simplification used to make the main point obvious. The destructor for the object is not called. I have tried a few combinations including * *. I managed to corrupt the heap at least once. Can this be fixed and work as desired or must each item be deleted one at a time without using the Delete_Stuff( … ) function.
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This application has several pointers to be deleted in the destructor. Each is logged when created and again when deleted to reduce the possibility of an undetected memory leak. As there are several, a function is needed to do the deletes. The goal is to avoid writing all that logging code multiple times. Below is the concept. The first time it was tried the subject was an instance of a class with its own destructor. A breakpoint was placed in that destructor.
Void Delete_Stuff( WCHAR * name, void * item )
{
If( item != NULL )
{
Write_Log_Entry( L”Preparing to delete <name> at address <*item>”); // please see note
delete ( item ); // does not call the destructor
delete ( *item ); // illegal indirection
}
}EDIT: I wrote the text up in MS word and did not notice that the leading character of "delete" had been capitalized. Apologies for that. Note: An swprintf_s(…) is used to build the string and the named function does the logging. Please accept the gross simplification used to make the main point obvious. The destructor for the object is not called. I have tried a few combinations including * *. I managed to corrupt the heap at least once. Can this be fixed and work as desired or must each item be deleted one at a time without using the Delete_Stuff( … ) function.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
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That is not the C++ delete Operator[^]. What is happening in your
Deletefunction?It stepped through the delete but the destructor for that class/object was not called. Note: I wrote the text up in MS word and did not notice that the leading character of "delete" had been capitalized. Apologies for that.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
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It stepped through the delete but the destructor for that class/object was not called. Note: I wrote the text up in MS word and did not notice that the leading character of "delete" had been capitalized. Apologies for that.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
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I do not have a delete function. The parens were used in an attempt to tell the standard delete operation that I want to delete the object pointed to by the pointer. An indirect delete rather than a direct delete.
class widget{ ... }
p_widget = new widget;
...
delete_stuff( L"widget", p_widget );
...
void delete_stuff( WCHAR * name, void * item )
{
delete *item;
... logging code not shown.
}The destructor of widget has a breakpoint that was never hit. I presume that widget was not deleted. Because that did not work, I tried dereferencing and grouping the pointer as in:
delete *item;
and
delete (*item);I am unable to get the breakpoint in the destructor so presume I am doing something wrong.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
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I do not have a delete function. The parens were used in an attempt to tell the standard delete operation that I want to delete the object pointed to by the pointer. An indirect delete rather than a direct delete.
class widget{ ... }
p_widget = new widget;
...
delete_stuff( L"widget", p_widget );
...
void delete_stuff( WCHAR * name, void * item )
{
delete *item;
... logging code not shown.
}The destructor of widget has a breakpoint that was never hit. I presume that widget was not deleted. Because that did not work, I tried dereferencing and grouping the pointer as in:
delete *item;
and
delete (*item);I am unable to get the breakpoint in the destructor so presume I am doing something wrong.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
I see the problem; my bad for missing it in your original question. Your function has the signature:
Void Delete_Stuff( WCHAR * name, void * item )
so when you call
delete itemthe compiler has no idea what typeitemis, so just throws it away. You can only calldeleteon an object, when it is specifically typed so the compiler knows how to deal with it. You may try casting it to the relevant class type, but you would need some way of telling your function what type each pointer is. -
I do not have a delete function. The parens were used in an attempt to tell the standard delete operation that I want to delete the object pointed to by the pointer. An indirect delete rather than a direct delete.
class widget{ ... }
p_widget = new widget;
...
delete_stuff( L"widget", p_widget );
...
void delete_stuff( WCHAR * name, void * item )
{
delete *item;
... logging code not shown.
}The destructor of widget has a breakpoint that was never hit. I presume that widget was not deleted. Because that did not work, I tried dereferencing and grouping the pointer as in:
delete *item;
and
delete (*item);I am unable to get the breakpoint in the destructor so presume I am doing something wrong.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
This is how it needs to be done:
// Object is a base class (that does not need to do anything)
class Object
{
public:
Object()
{
cout << "Object constructor" << endl;
};
virtual ~Object()
{
cout << "Object destructor" << endl;
};
};// Widget, and all other classes need to inherit Object
class Widget : Object
{
public:
Widget()
{
cout << "Widget constructor" << endl;
};
~Widget()
{
cout << "Widget destructor" << endl;
};
};// Delete_Stuff takes an Object pointer as its second parameter
static void Delete_Stuff(char* name, Object* object)
{
cout << "cleanup " << name << endl;// delete will now correctly delete any object delete object;}
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I see the problem; my bad for missing it in your original question. Your function has the signature:
Void Delete_Stuff( WCHAR * name, void * item )
so when you call
delete itemthe compiler has no idea what typeitemis, so just throws it away. You can only calldeleteon an object, when it is specifically typed so the compiler knows how to deal with it. You may try casting it to the relevant class type, but you would need some way of telling your function what type each pointer is.Then I cannot do that. Ok. thanks for taking the time to explain.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com
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Then I cannot do that. Ok. thanks for taking the time to explain.
Thank you for your time If you work with telemetry, please check this bulletin board: www.irigbb.com