This tutorial explains the C timeout stack by example.
Let’s dive into the details to get to the bottom of the “execution stack” by simply defining what it is and where is it always used one at a time? So! If we try to remind him of our memories during college, we find that the concept of the stack that we learned is behindIt is a lot like “whenever a function is undoubtedly called, a stack is created and” is used to temporarily store variables that are local to functions, arguments passed to a function, information returned, and so on. And when the function is completed, the corresponding battery is erased. Of course my statement is correct! It’s not finished yet!
Let’s start with “a.out”, a standard object for almost all C programs we compile on Linux and Unix systems! This file can be in ELF (Executable and Binding Format), COFF (Common Object File Format), or simply “a.out” data format. Although these file formats are of different formats, they always have one simple “segment concept”! A segment is a location in the binary file “a.out” that contains messages of a particular type for entries in the “symbol table” for whatever reason. Each segment can have different sections. Sections are the most compact organizational units in an ELF data file. Each segment contains elements related to the binary!
Run a specific timeline The memory on the stack is wasted: when we call a huge function in C, its activation records, that is, parameters, are pushed onto the execution stack, and when the function completes, the activation record is removed from the temporary stack.
Let’s write a simple “hello world” program, runuse it and run the command “size” in the executable file “a.out” to see which different segments are taking up and how much space.
Since it is free, the text segment requires 1144 bytes and the data segment 492 bytes. The bss segment is in 2007 bytes! It is interesting to note that you can experiment with the above program by additionally including global or static programs or global or uninitialized compiler and compiler programs and manipulating their size to ensure that the types of most operators fall into which segments! For example
Note that the text segment has not changed, while the data segment has changed accordingly with up to two global and permanently initialized instructions. Likewise, you can run some important tests that interest you, which instructions in your C program go to which different segments of the executable!
The following figure shows instructions in a new C program that correspond toindividual modules of web templates in the “a.out” file:
Note that the local conditions declared in the function do not match the “a.out” file. Instead, they are created at runtime, when the program is executed. Also note that the uninitialized global and stationary data correspond to the BSS. Bss is a good shorthand for “Block Started by Symbol”. Unlike a data segment, a BSS segment does not have an uninitialized data image, but only retains the amount of disk space required at runtime. The text segment contains exe statements in the C language of your program.
Which is an example of stack in C + +?
A stack is an abstract data structure that contains a collection of elements. The stack implements the LIFO system, that is, the element that is pushed to the end is removed first. Finally, the stack in the C ++ example | C ++ program and stack algorithm complete.
So gentlemen, so far we have seen that statements in a C program, after they have been compiled, correspond to different segments of the current executable. As we know, when a method is executed, it is executed in its own memory space allocated for it. Typically, this executable file should be placed in the address space of the executable program. But how does this happen? Who is this guy? This is where the linker and bootstrap appear in the picture.a car! In fact, they do it all! Let’s see how?
The segments of the “a.out” file are conveniently mapped to objects that the runtime linker loads directly! The loader takes almost only one segment of the image into the file and also puts it directly into memory. Segments actually become areas of memory in a running program, each with a specific purpose.
What was the role of the runtime system in C?
In C and later languages that support heap sharing, the run-time system also contained a directory that managed the program’s memory pool. In object-oriented programming languages, the runtime engine was often also responsible for checking dynamic classification and resolving method references.
The following figure shows how the segments other than “a.out” are organized in memory.
The text contains the instructions of the program. The loader copies it directly from the application memory to the system normally attached to the “mmap ()” system, and never cares about it again, since the program code usually does not change its valuable content or size.
While the entire program is running, the execution stack stores some pretty important information for each of the current calls to the match function. Whenever the function is calledI am during program execution, saving: return value (if any)
The initialized data segment contains global and static variables with an assigned philosophy. The BSS segment size is now obtained from the executable file, and the entire loader receives a block of this size, placing it immediately after the data segment. This section is immediately discarded as soon as it inserts I’m in the program. ™ indicate part. The entire data link and beyond, the BSS segment is commonly referred to as the data segment at this point. Indeed, from an operating system memory management perspective, a segment is simply a set of sequential virtual addresses, so the following segments are concatenated. The data segment should generally be the largest segment in almost all processes!
Now let’s see how the town variables, parameters passing function calls, duplicate addresses, temporary addresses, and so on are stored. So we still need a placeholder for the stack segment! We may also need a heap for heap allocation. This is often set the first time malloc () is called.
The runtime collection is used to transfer / return values to / from disks. When passing arguments to a function, for example, when returning values from a function, we use the execution stack. If the types allow it, elements passed by reference in a function can be identified as being manipulated to change their value.
Note in the form of fig. 2, it can be seen that the lower part of the room addresses is not shown, i.e. it lies in a wide variety of process address space, but has no physical processing, so any reference to it is illegal! This is usually a few kilobytes of memory, starting at address zero. It intercepts references through memory with A null pointer, which has small integer values, and so on. This
After a while, the program will be in memory and will be executed. Now let’s see how C organizes the data structures of a running program. There are several runtime data structures: stack, records, activation heap, and so on. Remember that this is where we “stack the segments” …
A stack segment has a unique data structure – a stack. We already know the classic communication, how the stack works, in the case of a callback like LIFO, last in – first out. Two different operations are performed on the stack, viz. Pushes something onto the stack while other POPs pop an item off the top of the stack. The PUSH operation increases the stack.
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A function can access market variables to locate its caller using parameters, possibly global pointers. The runtime maintains a clause, often in a register and usually called SP (Stack Pointer) once, which indicates what I would call the current top of the stack. The entire load segment of the euThere are three main uses, two of which are functionally broken and the last one for evaluating expressions.
1. The stack provides storage of local variables in
