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How to analyze the creation and destruction of C language function stack frames? in view of this problem, this article introduces the corresponding analysis and solutions in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

The following are some of the problems we have come into contact with but do not understand:

1. Why local variables are random before they are assigned.

two。 The process of creating local variables.

3. The function passes parameters, the order of passing parameters,

4. What is the relationship between the shape and the actual parameter.

5. How the calling function is called and what is the procedure of the call.

6. How it is returned after the call function is finished.

These questions may not come into contact with us at school, nor will they appear on the examination papers, but as computer majors, it is necessary to know and understand them. This is equivalent to our internal skills, in the future in-depth study, we will be able to understand and understand more quickly. The following is the whole process of function call. After learning, there is an answer to the above question.

The function stack frame is the space that the system allocates to the function, and the address is stored.

Esp ebp, on the other hand, is used to maintain function stack frames.

Esp ebp, like eax ebx ecx edx, is the register of the system and has a certain storage function.

Let's take this function as an example.

Int Add (int Xreint y) {int zonal 0; zonal x quoy; return z;} int main () {int axiom 10; int baud 20; int cantilever 0; c=Add (a dint b); printf ("% d\ n", c); return 0;}

The main function is the same as other functions, and the main function is also the called function.

The basic logic is that mainCRTStartup calls _ tmainCRTStartup to call the main function.

When the program is running, ebp and ebp maintain _ tmainCRTStartup. At first, esp is in the position of the pointer at the top of the stack, while ebp is at the bottom of the stack.

First of all, push, continue the stack operation, print the address of ebp to the location of esp, and then replace the value of esp to ebp, esp plus the memory number of oE4h, to form the following figure.

At this point, ebp and esp will maintain the main function, push the stack three times and press the ebx,esi,edi to the top of the stack. Its purpose is to make the system run normally.

The next step is the operation of lev mov mov, which changes the contents of the space between esp and ebp to cccccc, which is why the values of variables are random before they are defined.

The next step is to define the variable abc, so how does the system leave room for abc to define in the stack area? This is achieved in the following three steps. This allocates space for abc.

The result is as shown in the picture

When abc is defined, the next step is the function call, the process of passing parameters to the function.

The system first puts the value of ab in the register of eax ecx.

The following operation is similar to opening up space with the main function.

The blue part below is the process of passing parameters to the function, which is easy to know by the diagram. The parameter passed by the function actually stores the value of ab in the register and temporarily copies it to x and y.

At this point, the location of the ebp-8 is the space where z is located, and then stored in the register.

Then the edi esi ebx pops up, the address of the ebp is passed to the esp, and then the ebp pops up, and ebp and esp return to their original location to maintain the main function again.

Pass the value of z stored in the register to c

This is the answer to the question on how to create and destroy the C language function stack frame. I hope the above content can be of some help to you, if you still have a lot of doubts to be solved. You can follow the industry information channel for more related knowledge.

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