Preface

As a non subject student , Let me say before that I don't know the difference between different storage , Just vaguely understand what the stack is and what the heap is , But these foundations are also very important , A general understanding allows us to have new ideas when solving some problems .

One 、 Several segments stored

Different variables and different operations apply for different spatial positions , Here is a brief introduction to the general storage content of each space .

The stack area ： Generally, it is used as the location where some temporary variables are stored during program compilation , The size is generally 2m or 1M.

Heap area ： Completely controlled by the programmer malloc The opened memory is concentrated in the heap , It's usually 2G about .

code paragraph ： The code we write is stored in this place .

rodata paragraph ： Where some constants are stored .

data paragraph ： Where class variables are stored , For the time being, it can be understood as except rodata Everything in it is here , Here's about static I'll talk more about it in other articles later .

Two 、rodata Segment and data The difference caused by paragraph

Through the introduction above , We know rodata Is where constants are stored , This area is only allowed to read but not write , Therefore, the defined constants cannot be modified , Here is a code to explain .

#include <stdio.h>

int main()
{
    char *s = "hiHiHi";
    s[0] = 'H';
    printf("%s",s);
}

This sentence is actually wrong , Before you understand that different variables will be stored in different locations , I certainly don't understand why this went wrong , Let's look at the correct code first .

#include <stdio.h>

int main()
{
    char s[] = "hiHiHi";
    s[0] = 'H';
    printf("%s",s);
}

Pointers and arrays are replaced here , Why did you let this program pass ？ When it was originally a pointer, this string of data was stored according to a constant , Nature will exist rodata paragraph , And that position is read-only and not written , So you can't change , And the array is in data Segment stored data , It will change naturally .

summary

The understanding of spatial attributes can give us more ideas when solving problems , As the basic skill of writing programs, it is very important , It's not about static Etc , This part will appear in later articles .