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The content of this article mainly focuses on how to understand the memory management of CAccord Category +. The content of the article is clear and well-organized. It is very suitable for beginners to learn and is worth reading. Interested friends can follow the editor to read together. I hope you can get something through this article!

Candlespace + memory distribution

Int globalVar = 1 posistatic int staticGlobalVar = 1 char* pChar3 void Test () {static int staticVar = 1 setint localVar = 1 setint num1 [10] = {1,2,3,4}; char char2 [] = "abcd"; char* pChar3 = "abcd"; int* ptr1 = (int*) malloc (sizeof (int) * 4); int* ptr2 = (int*) calloc (4, sizeof (int)); int* ptr3 = (int*) realloc (ptr2, sizeof (int) * 4); free (ptr1); free (ptr3);}

Exercise

1. Multiple choice questions: options: A. Stack B. Pile C. Data segment (static zone) D. Where is the code snippet (constant area) globalVar? Where is _ _ clocked _ staticGlobalVar? Where is _ _ clocked _ staticVar? Where is _ _ clocked _ localVar? Where is _ _ averted _ num1? Where is _ _ averted _ char2? _ _ ordered _ * where is char2? _ affected _ pChar3 where is it? _ pChar3 _ * where is it? Where is _ _ dumped _ ptr1? _ _ ordered _ * where is ptr1? _ _ B__2. Fill in the blanks: (32-bit program) sizeof (num1) = _ _ 40; sizeof (char2) = _ _ 5; strlen (char2) = _ _ 4; sizeof (pChar3) = _ _ 4; strlen (pChar3) = _ _ 4; sizeof (ptr1) = _ _ 4

1. The stack is also known as the stack, non-static local variables, function parameters, return values, and so on. The stack grows downward.

two。 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.

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

4. Data segments-stores global and static data.

5. Code snippet-executable code / read-only constant

Dynamic memory Management in C language

What is the difference between malloc, calloc and realloc?

Calloc is initialized, which is equivalent to malloc + memset, initialized by bytes, and each byte of the space is initialized to 0.

Realloc expansion can be divided into in-situ expansion and remote expansion.

C++ memory management mode

Apply for and free space for individual elements, using new and delete operators, apply for and free contiguous space, and use new [] and delete [].

Int* p1 = new int (5)

Dynamically apply for an int space, which is initialized to 5.

Int* p2 = new int [5]

Dynamically apply for 5 int spaces.

Int* p3 = new int [5] {1pm 2pm 3pm 4pm 5}

Give the initial value

Custom types for new and delete operations

When requesting space of a custom type, new calls the constructor, delete calls the destructor, and malloc and free do not.

Operator new and operator delete function

New and delete are operators for dynamic memory request and release, and operator new and operator delete are global functions provided by the system.

New calls the operator new global function at the bottom to request space, and delete uses the operator delete global function to free up space at the bottom.

Operator new: this function applies for space through malloc, and returns directly when malloc applies for space successfully. If you fail to apply for space, you try to implement the measures to deal with the shortage of space. If the response is set by the user, you can apply, otherwise you will run abnormally.

Operator delete: this function ultimately frees up space through free.

The implementation principle of new and delete 1. Built-in type

If you are applying for a built-in type of space, new and malloc, delete and free are basically similar, except that new/delete applies for and releases space for a single element.

New [] and delete [] apply for contiguous space, and new throws an exception when it fails to apply for space, and malloc returns NULL.

two。 Custom type

New principle

1. Call the operator new function to apply for space

two。 Execute the constructor on the applied space to complete the construction of the object.

The principle of delete

1. Execute the destructor in space to clean up the resources in the object.

two。 Call the operator delete function to free up the object's space.

The principle of new T [N]

1. Call the operator new [] function, and actually call the operator new function in operator new [] to complete the application of N object spaces.

two。 Execute the N-time constructor on the applied space

Principle of delete []

1. Execute the N-th destructor on the released object space to clean up the resources in N objects.

two。 Call operator delete [] to free up space, and actually call operator delete in operator delete [] to free up space

The difference between malloc/free and new/delete

What malloc/free and new/delete have in common is that both request space from the heap and require the user to release it manually.

The differences are:

1.malloc and free are functions, new and delete are operators

The space requested by 2.malloc will not be initialized. New can initialize it.

When 3.malloc applies for space, it needs to manually calculate the size of the space and pass it. New only needs to follow the type of space after it.

The return value of 4.malloc is that void*, must be forced in use, but new does not need it, because new is followed by the type of space.

When 5.malloc fails to apply for space, it returns NULL, so it must be empty when using it. New does not need it, but new needs to catch exceptions.

6. When applying for custom type objects, malloc/free will only open up space and will not call constructors and destructors, while new will call constructors to complete the initialization of objects after applying for space, and delete will call destructors to clean up resources in space before releasing space.

What is C language? C language is a process-oriented and abstract general programming language, which is widely used in low-level development. C language can be used to compile and process low-level memory in a simple way.

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