How to understand the memory management of C++

Today, I will talk to you about how to understand the memory management of C++, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following for you. I hope you can get something from this article.

1. C _ blank + memory distribution

Stack, also known as stack, non-static local variables / function parameters / return values, etc., the stack is growing downward.

The memory mapping segment is an efficient Ithumb O mapping method for loading a shared dynamic memory library. Users can use the system interface to create shared memory and do inter-process communication.

The heap is used for dynamic memory allocation while the program is running, and the heap can grow upward.

Data segments-stores global and static data.

Code snippet-executable code / read-only constant.

2. Dynamic memory management in C language: 1. Malloc/calloc/realloc difference:

What they have in common:

They are all library functions used for dynamic memory request in C language, and the applied space is all on the heap. After using them, free must be used to release them.

The return value type is void*, which must be forcibly transferred when accepting the returned address.

If the application for space is successful: the first address of the space is returned, and NULL is returned if it fails.

Differences:

Malloc: return value type void*

Forced transfer must be made when accepting the returned space address

Success: space first address failed: NULL

Parameter: the total number of bytes of space requested

The requested space is on the heap, and you must use free to release it after use.

Calloc: the returned values are consistent

Parameter list: parameter 1 represents the number of elements; parameter 2 represents the number of bytes of a single type

Function: basically the same as malloc, but calloc initializes the space it applies for

Realloc (void* p, size_t size): resizes the space pointed to by p to sizebytes

P points to NULL: this function is similar to malloc

Suppose: P points to a total of old bytes

Size directly returns the first address of the space to which the value p points

Size > old: expands the space pointed to by p to size bytes

Larger: return to the first address of the original space

Much larger: apply for new space; copy elements from the old space to the new space; free up the old space; return to the first address of the new space

Dynamic memory management in C++: new/delete

Why does C++ want to develop a set of dynamic memory management?

First of all: dynamic memory management in C language can still be used in C++.

Reason:

1. The method in C language is troublesome-the user needs to count the bytes manually, the returned result needs to be strongly changed, null is needed, and the header file needs to be included.

2. Malloc, free: constructors / destructors are not called; new, delete: constructors and destructors are called during space application and release

/ / dynamic memory management in C++: new/delete---- applies for a single type of space / / new [] / delete []-applies for the release of a continuous space / / Note: 1. New/delete is not a function Is the keyword in C++ | | operator / / 2, the space of new must have delete to release new [] you must use delete [] to release class Test {public: Test (): _ t (10) {cout