Why would a new[] expression ever invoke a destructor?
From the C++17 standard (draft here), [expr.new]:
If the new-expression creates an object or an array of objects of class type, access and ambiguity control are done for the allocation function, the deallocation function, and the constructor. If the new-expression creates an array of objects of class type, the destructor is potentially invoked.
Why would new invoke a destructor? It's new, after all. It isn't delete.
c++ c++17 new-operator
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
add a comment |
From the C++17 standard (draft here), [expr.new]:
If the new-expression creates an object or an array of objects of class type, access and ambiguity control are done for the allocation function, the deallocation function, and the constructor. If the new-expression creates an array of objects of class type, the destructor is potentially invoked.
Why would new invoke a destructor? It's new, after all. It isn't delete.
c++ c++17 new-operator
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
add a comment |
From the C++17 standard (draft here), [expr.new]:
If the new-expression creates an object or an array of objects of class type, access and ambiguity control are done for the allocation function, the deallocation function, and the constructor. If the new-expression creates an array of objects of class type, the destructor is potentially invoked.
Why would new invoke a destructor? It's new, after all. It isn't delete.
c++ c++17 new-operator
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
From the C++17 standard (draft here), [expr.new]:
If the new-expression creates an object or an array of objects of class type, access and ambiguity control are done for the allocation function, the deallocation function, and the constructor. If the new-expression creates an array of objects of class type, the destructor is potentially invoked.
Why would new invoke a destructor? It's new, after all. It isn't delete.
c++ c++17 new-operator
c++ c++17 new-operator
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
edited Mar 22 at 20:44
Cody Gray♦
195k35383475
195k35383475
asked Mar 22 at 20:32
thbthb
8,90532457
asked Mar 22 at 20:32
thbthb
8,90532457
asked Mar 22 at 20:32
thbthb
8,90532457
8,90532457
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
If construction of any object in the buffer throws an exception, the previously constructed objects must be destructed. That requires an available destructor.
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-arraynewdoesn't require an available d'tor.
– StoryTeller
yesterday
add a comment |
You have not considered the word "potentially" in the quote you have mentioned from the standard.
It means that there is a possibility that invocation of the destructor can happen. And it will happen if construction of any object in the array throws an exception.
Combined with the following quote from [class.dtor]/12.4 which mentions [expr.new], this becomes clear.
In each case, the context of the invocation is the context of the construction of the object. A destructor is also invoked implicitly through use of a delete-expression for a constructed object allocated by a new-expression; the context of the invocation is the delete-expression. [ Note: An array of class type contains several subobjects for each of which the destructor is invoked. — end note ] A destructor can also be invoked explicitly. A destructor is potentially invoked if it is invoked or as specified in
[expr.new],[class.base.init], and[except.throw]. A program is ill-formed if a destructor that is potentially invoked is deleted or not accessible from the context of the invocation.
answered Mar 23 at 7:59
P.WP.W
17.6k41657
It is a bit too wordy for a simple answer though...
– sophros
yesterday
add a comment |
In action:
#include <iostream>
int counter;
class Destruct
{
public:
Destruct()
{
if (counter++ > 5)
throw counter;
}
~Destruct()
{
std::cout << "Dtor calledn";
}
};
int main()
{
try
{
new Destruct[10];
}
catch (...){}
}
You'll see output something like:
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
answered 2 days ago
AjayAjay
13.6k84179
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
If construction of any object in the buffer throws an exception, the previously constructed objects must be destructed. That requires an available destructor.
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-arraynewdoesn't require an available d'tor.
– StoryTeller
yesterday
add a comment |
If construction of any object in the buffer throws an exception, the previously constructed objects must be destructed. That requires an available destructor.
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-arraynewdoesn't require an available d'tor.
– StoryTeller
yesterday
add a comment |
If construction of any object in the buffer throws an exception, the previously constructed objects must be destructed. That requires an available destructor.
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
If construction of any object in the buffer throws an exception, the previously constructed objects must be destructed. That requires an available destructor.
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
edited Mar 22 at 20:35
Sombrero Chicken
24.7k33281
24.7k33281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
answered Mar 22 at 20:34
StoryTellerStoryTeller
104k12218281
104k12218281
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-arraynewdoesn't require an available d'tor.
– StoryTeller
yesterday
add a comment |
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-arraynewdoesn't require an available d'tor.
– StoryTeller
yesterday
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
For clarification: Does this mean that a new (non-array) could also potentially call the destructor? I believe so from what I am seeing but wanted to ensure myself it is true.
– Daniel Robert Miller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-array
new doesn't require an available d'tor.– StoryTeller
yesterday
@DanielRobertMiller - An object not fully constructed won't have its destructor called. A non-array
new doesn't require an available d'tor.– StoryTeller
yesterday
add a comment |
You have not considered the word "potentially" in the quote you have mentioned from the standard.
It means that there is a possibility that invocation of the destructor can happen. And it will happen if construction of any object in the array throws an exception.
Combined with the following quote from [class.dtor]/12.4 which mentions [expr.new], this becomes clear.
In each case, the context of the invocation is the context of the construction of the object. A destructor is also invoked implicitly through use of a delete-expression for a constructed object allocated by a new-expression; the context of the invocation is the delete-expression. [ Note: An array of class type contains several subobjects for each of which the destructor is invoked. — end note ] A destructor can also be invoked explicitly. A destructor is potentially invoked if it is invoked or as specified in
[expr.new],[class.base.init], and[except.throw]. A program is ill-formed if a destructor that is potentially invoked is deleted or not accessible from the context of the invocation.
answered Mar 23 at 7:59
P.WP.W
17.6k41657
It is a bit too wordy for a simple answer though...
– sophros
yesterday
add a comment |
You have not considered the word "potentially" in the quote you have mentioned from the standard.
It means that there is a possibility that invocation of the destructor can happen. And it will happen if construction of any object in the array throws an exception.
Combined with the following quote from [class.dtor]/12.4 which mentions [expr.new], this becomes clear.
In each case, the context of the invocation is the context of the construction of the object. A destructor is also invoked implicitly through use of a delete-expression for a constructed object allocated by a new-expression; the context of the invocation is the delete-expression. [ Note: An array of class type contains several subobjects for each of which the destructor is invoked. — end note ] A destructor can also be invoked explicitly. A destructor is potentially invoked if it is invoked or as specified in
[expr.new],[class.base.init], and[except.throw]. A program is ill-formed if a destructor that is potentially invoked is deleted or not accessible from the context of the invocation.
answered Mar 23 at 7:59
P.WP.W
17.6k41657
It is a bit too wordy for a simple answer though...
– sophros
yesterday
add a comment |
You have not considered the word "potentially" in the quote you have mentioned from the standard.
It means that there is a possibility that invocation of the destructor can happen. And it will happen if construction of any object in the array throws an exception.
Combined with the following quote from [class.dtor]/12.4 which mentions [expr.new], this becomes clear.
In each case, the context of the invocation is the context of the construction of the object. A destructor is also invoked implicitly through use of a delete-expression for a constructed object allocated by a new-expression; the context of the invocation is the delete-expression. [ Note: An array of class type contains several subobjects for each of which the destructor is invoked. — end note ] A destructor can also be invoked explicitly. A destructor is potentially invoked if it is invoked or as specified in
[expr.new],[class.base.init], and[except.throw]. A program is ill-formed if a destructor that is potentially invoked is deleted or not accessible from the context of the invocation.
answered Mar 23 at 7:59
P.WP.W
17.6k41657
You have not considered the word "potentially" in the quote you have mentioned from the standard.
It means that there is a possibility that invocation of the destructor can happen. And it will happen if construction of any object in the array throws an exception.
Combined with the following quote from [class.dtor]/12.4 which mentions [expr.new], this becomes clear.
In each case, the context of the invocation is the context of the construction of the object. A destructor is also invoked implicitly through use of a delete-expression for a constructed object allocated by a new-expression; the context of the invocation is the delete-expression. [ Note: An array of class type contains several subobjects for each of which the destructor is invoked. — end note ] A destructor can also be invoked explicitly. A destructor is potentially invoked if it is invoked or as specified in
[expr.new],[class.base.init], and[except.throw]. A program is ill-formed if a destructor that is potentially invoked is deleted or not accessible from the context of the invocation.
answered Mar 23 at 7:59
P.WP.W
17.6k41657
answered Mar 23 at 7:59
P.WP.W
17.6k41657
answered Mar 23 at 7:59
P.WP.W
17.6k41657
answered Mar 23 at 7:59
P.WP.W
17.6k41657
17.6k41657
It is a bit too wordy for a simple answer though...
– sophros
yesterday
add a comment |
It is a bit too wordy for a simple answer though...
– sophros
yesterday
It is a bit too wordy for a simple answer though...
– sophros
yesterday
It is a bit too wordy for a simple answer though...
– sophros
yesterday
add a comment |
In action:
#include <iostream>
int counter;
class Destruct
{
public:
Destruct()
{
if (counter++ > 5)
throw counter;
}
~Destruct()
{
std::cout << "Dtor calledn";
}
};
int main()
{
try
{
new Destruct[10];
}
catch (...){}
}
You'll see output something like:
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
answered 2 days ago
AjayAjay
13.6k84179
add a comment |
In action:
#include <iostream>
int counter;
class Destruct
{
public:
Destruct()
{
if (counter++ > 5)
throw counter;
}
~Destruct()
{
std::cout << "Dtor calledn";
}
};
int main()
{
try
{
new Destruct[10];
}
catch (...){}
}
You'll see output something like:
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
answered 2 days ago
AjayAjay
13.6k84179
add a comment |
In action:
#include <iostream>
int counter;
class Destruct
{
public:
Destruct()
{
if (counter++ > 5)
throw counter;
}
~Destruct()
{
std::cout << "Dtor calledn";
}
};
int main()
{
try
{
new Destruct[10];
}
catch (...){}
}
You'll see output something like:
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
answered 2 days ago
AjayAjay
13.6k84179
In action:
#include <iostream>
int counter;
class Destruct
{
public:
Destruct()
{
if (counter++ > 5)
throw counter;
}
~Destruct()
{
std::cout << "Dtor calledn";
}
};
int main()
{
try
{
new Destruct[10];
}
catch (...){}
}
You'll see output something like:
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
Dtor called
answered 2 days ago
AjayAjay
13.6k84179
answered 2 days ago
AjayAjay
13.6k84179
answered 2 days ago
AjayAjay
13.6k84179
answered 2 days ago
AjayAjay
13.6k84179
13.6k84179
add a comment |
add a comment |
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