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Is delete *p an alternative to delete [] p?

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11

The following code is from the Microsoft Documentation

int (**p) () = new (int (*[7]) ());
delete *p;

I think that delete [] p should be used here instead.

Is delete *p the same as delete [] p?

c++ arrays

share|improve this question

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  delete *p differs from delete [] p.
  
  – Jarod42
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You're right. They're not the same.
  
  – Cruz Jean
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  typedef would make thing clearer.
  
  – Jarod42
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Anyway p[0] is not initialized. They have typo.
  
  – Jarod42
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  delete[] what was new[]ed and delete what was newed. Though in modern code you should avoid most uses of new, it's no longer the preferred way of dynamically creating objects. See std::make_unique and std::make_shared instead or use a standard container.
  
  – François Andrieux
  7 hours ago
  
  

  
  
  
  

add a comment | 

11

The following code is from the Microsoft Documentation

int (**p) () = new (int (*[7]) ());
delete *p;

I think that delete [] p should be used here instead.

Is delete *p the same as delete [] p?

c++ arrays

share|improve this question

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  delete *p differs from delete [] p.
  
  – Jarod42
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You're right. They're not the same.
  
  – Cruz Jean
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  typedef would make thing clearer.
  
  – Jarod42
  7 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Anyway p[0] is not initialized. They have typo.
  
  – Jarod42
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  delete[] what was new[]ed and delete what was newed. Though in modern code you should avoid most uses of new, it's no longer the preferred way of dynamically creating objects. See std::make_unique and std::make_shared instead or use a standard container.
  
  – François Andrieux
  7 hours ago
  
  

  
  
  
  

add a comment | 

The following code is from the Microsoft Documentation

int (**p) () = new (int (*[7]) ());
delete *p;

I think that delete [] p should be used here instead.

Is delete *p the same as delete [] p?

c++ arrays

share|improve this question

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

int (**p) () = new (int (*[7]) ());
delete *p;

share|improve this question

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

share|improve this question

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

edited 7 hours ago

Guillaume Racicot

16.1k53871

edited 7 hours ago

Guillaume Racicot

16.1k53871

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

asked 7 hours ago

xiaokaoyxiaokaoy

7152719

2 Answers
2

active

oldest

votes

12

That code is invalid C++, because only pointers-to-objects can be deleted. *p has type int (*)(), which is a function pointer, not a pointer to an object.

Even MSVC itself does not compile it, even in permissive mode:

error C2541: 'delete': cannot delete objects that are not pointers

They should have used delete [] instead.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

AcornAcorn

6,20111341

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  In what context one may need to dynamically allocate pointers to functions?
  
  – Ayxan
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan That would be another question, but for instance you may want to have a list of arbitrary operations to execute.
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan I have quickly posted it here: stackoverflow.com/q/55524710/9305398
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Even though this is specific to MSVC, g++ gives the following similar error when trying to compile: error: cannot delete expression of type 'int (*)()' .. seems odd that MS would have missed something that simple in their docs :/
  
  – txtechhelp
  5 hours ago
  
  

  
  
  
  

add a comment | 

-4

1. This code specifically has a different issue as it tries to delete an inner element of an array so it will not compile. It would compile if you wrote delete p and not delete *p.


2. You can use simple delete on an object allocated by new [] if It is an array of primitive types. Bad practice, ugly, yes. But not a mistake.


3. The difference between delete and delete [] is that the former also calls destructors. For primitive types, however, it will call simple delete to free the memory internally anyway.


4. Again, even if it works, you should avoid mixing operator types.

share|improve this answer

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  delete [] calls destructors...
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Mixing operators is undefined behavior.
  
  – Ayxan
  6 hours ago
  

  
  
  
  

add a comment | 

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12

That code is invalid C++, because only pointers-to-objects can be deleted. *p has type int (*)(), which is a function pointer, not a pointer to an object.

Even MSVC itself does not compile it, even in permissive mode:

error C2541: 'delete': cannot delete objects that are not pointers

They should have used delete [] instead.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

AcornAcorn

6,20111341

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  In what context one may need to dynamically allocate pointers to functions?
  
  – Ayxan
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan That would be another question, but for instance you may want to have a list of arbitrary operations to execute.
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan I have quickly posted it here: stackoverflow.com/q/55524710/9305398
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Even though this is specific to MSVC, g++ gives the following similar error when trying to compile: error: cannot delete expression of type 'int (*)()' .. seems odd that MS would have missed something that simple in their docs :/
  
  – txtechhelp
  5 hours ago
  
  

  
  
  
  

add a comment | 

12

That code is invalid C++, because only pointers-to-objects can be deleted. *p has type int (*)(), which is a function pointer, not a pointer to an object.

Even MSVC itself does not compile it, even in permissive mode:

error C2541: 'delete': cannot delete objects that are not pointers

They should have used delete [] instead.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

AcornAcorn

6,20111341

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  In what context one may need to dynamically allocate pointers to functions?
  
  – Ayxan
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan That would be another question, but for instance you may want to have a list of arbitrary operations to execute.
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Ayxan I have quickly posted it here: stackoverflow.com/q/55524710/9305398
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Even though this is specific to MSVC, g++ gives the following similar error when trying to compile: error: cannot delete expression of type 'int (*)()' .. seems odd that MS would have missed something that simple in their docs :/
  
  – txtechhelp
  5 hours ago
  
  

  
  
  
  

add a comment | 

That code is invalid C++, because only pointers-to-objects can be deleted. *p has type int (*)(), which is a function pointer, not a pointer to an object.

Even MSVC itself does not compile it, even in permissive mode:

error C2541: 'delete': cannot delete objects that are not pointers

They should have used delete [] instead.

share|improve this answer

edited 7 hours ago

answered 7 hours ago

AcornAcorn

6,20111341

error C2541: 'delete': cannot delete objects that are not pointers

share|improve this answer

edited 7 hours ago

answered 7 hours ago

AcornAcorn

6,20111341

answered 7 hours ago

AcornAcorn

6,20111341

answered 7 hours ago

AcornAcorn

6,20111341

-4

1. This code specifically has a different issue as it tries to delete an inner element of an array so it will not compile. It would compile if you wrote delete p and not delete *p.


2. You can use simple delete on an object allocated by new [] if It is an array of primitive types. Bad practice, ugly, yes. But not a mistake.


3. The difference between delete and delete [] is that the former also calls destructors. For primitive types, however, it will call simple delete to free the memory internally anyway.


4. Again, even if it works, you should avoid mixing operator types.

share|improve this answer

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  delete [] calls destructors...
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Mixing operators is undefined behavior.
  
  – Ayxan
  6 hours ago
  

  
  
  
  

add a comment | 

-4

1. This code specifically has a different issue as it tries to delete an inner element of an array so it will not compile. It would compile if you wrote delete p and not delete *p.


2. You can use simple delete on an object allocated by new [] if It is an array of primitive types. Bad practice, ugly, yes. But not a mistake.


3. The difference between delete and delete [] is that the former also calls destructors. For primitive types, however, it will call simple delete to free the memory internally anyway.


4. Again, even if it works, you should avoid mixing operator types.

share|improve this answer

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  delete [] calls destructors...
  
  – Acorn
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Mixing operators is undefined behavior.
  
  – Ayxan
  6 hours ago
  

  
  
  
  

add a comment | 

1. This code specifically has a different issue as it tries to delete an inner element of an array so it will not compile. It would compile if you wrote delete p and not delete *p.


2. You can use simple delete on an object allocated by new [] if It is an array of primitive types. Bad practice, ugly, yes. But not a mistake.


3. The difference between delete and delete [] is that the former also calls destructors. For primitive types, however, it will call simple delete to free the memory internally anyway.


4. Again, even if it works, you should avoid mixing operator types.

share|improve this answer

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

share|improve this answer

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614

answered 6 hours ago

Yuri NudelmanYuri Nudelman

1,4061614