Tweak "Raw pointers (C++)" topic #5574
Conversation
…elete` in "Raw pointers (C++)"
… in "Raw pointers (C++)"
|
@Rageking8 : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. |
prmerger-automator
bot
added
Change sent to author
cpp-lang/subsvc
visual-cpp/svc
labels
|
Learn Build status updates of commit c3195c9: ✅ Validation status: passed
For more details, please refer to the build report. |
| @@ -19,7 +19,7 @@ A pointer can also be *dereferenced* to retrieve the value of the object that it | |||
| int j = *p; // dereference p to retrieve the value at its address | |||
| ``` | |||
|
|
|||
| A pointer can point to a typed object or to **`void`**. When a program allocates an object on the [heap](https://wikipedia.org/wiki/Heap) in memory, it receives the address of that object in the form of a pointer. Such pointers are called *owning pointers*. An owning pointer (or a copy of it) must be used to explicitly free the heap-allocated object when it's no longer needed. Failure to free the memory results in a *memory leak*, and renders that memory location unavailable to any other program on the machine. Memory allocated using **`new`** must be freed by using **`delete`** (or **`delete[]`**). For more information, see [`new` and `delete` operators](new-and-delete-operators.md). | |||
| A pointer can point to a typed object or to **`void`**. When a program allocates an object on the [heap](https://wikipedia.org/wiki/Heap) in memory, it receives the address of that object in the form of a pointer. Such pointers are called *owning pointers*. An owning pointer (or a copy of it) must be used to explicitly free the heap-allocated object when it's no longer needed. Failure to free the memory results in a *memory leak*, and renders that memory location unavailable to any other program on the machine. Memory allocated with **`new`** must be freed using **`delete`**, and memory allocated with **`new[]`** must be freed using **`delete[]`**. For more information, see [`new` and `delete` operators](new-and-delete-operators.md). | |||
There was a problem hiding this comment.
Memory allocated using
newmust be freed by usingdelete(ordelete[]).
This implies delete[] can be used in place of delete, which is wrong. Hence, this sentence is extended to make it explicit that new must be matched with delete, and new[] must be matched with delete[].
| @@ -78,7 +78,7 @@ void func_B(MyClass mc) | |||
| // This statement modifies only the local copy of mc. | |||
| mc.num = 21; | |||
| std::cout << "Local copy of mc:"; | |||
| mc.print(); // "Erika, 21" | |||
| mc.print(); // "Erika:21" | |||
There was a problem hiding this comment.
The output comments used the wrong delimiter (", " instead of the correct ":"). All subsequent occurrences are fixed.
| delete pmc; // don't forget to give memory back to operating system! | ||
| // delete pmc2; //crash! memory location was already deleted |
There was a problem hiding this comment.
Prefer the more idiomatic delete expr; over delete(expr);, even though the latter technically works. As an aside, found this interesting comment at c++ - Is there any difference between delete x and delete(x)? - Stack Overflow.
| @@ -156,7 +156,11 @@ int main() | |||
| } | |||
| ``` | |||
|
|
|||
| Certain arithmetic operations can be used on non-`const` pointers to make them point to another memory location. Pointers are incremented and decremented using the **`++`**, **`+=`**, **`-=`** and **`--`** operators. This technique can be used in arrays and is especially useful in buffers of untyped data. A `void*` gets incremented by the size of a **`char`** (1 byte). A typed pointer gets incremented by size of the type it points to. | |||
There was a problem hiding this comment.
A
void*gets incremented by the size of achar(1 byte).
This implies that pointer arithmetic can be done on void*, but that causes a hard error, since it is non-standard and only available as an extension on GCC (not sure if this extension exists for MSVC). Hence, this sentence is removed, but we can consider explicitly stating that it is not allowed.
| @@ -156,7 +156,11 @@ int main() | |||
| } | |||
| ``` | |||
|
|
|||
| Certain arithmetic operations can be used on non-`const` pointers to make them point to another memory location. Pointers are incremented and decremented using the **`++`**, **`+=`**, **`-=`** and **`--`** operators. This technique can be used in arrays and is especially useful in buffers of untyped data. A `void*` gets incremented by the size of a **`char`** (1 byte). A typed pointer gets incremented by size of the type it points to. | |||
| ```Output | |||
| 1 2 3 4 5 | |||
There was a problem hiding this comment.
There is a trailing space here as that's the verbatim output of this snippet.
|
Can you review the proposed changes? IMPORTANT: When the changes are ready for publication, adding a #label:"aq-pr-triaged" |
prmerger-automator
bot
added
the
aq-pr-triaged
Fix a bunch of mistakes and perform some improvements. See review comments for more information.