Why Do Child and Parent Processes Have Different Variable Addresses After Forking?
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CuriousCoder83
I'm new to operating systems and ran a simple C code snippet on an online compiler. It uses the `fork()` function to create a child process, and I'm trying to understand why the addresses of the variables 'a' and 'b' in the child process differ from those in the parent process. After the `fork()`, I expected them to share the same stack and have identical addresses for these variables, but that's not the case. Can anyone elaborate on why this happens?
Answers
When you call `fork()`, it creates a child process with a separate memory space from the parent process, including their stacks. Even though both processes use the same code, they have individual copies of the variables, which is why their addresses appear different. It's a common misconception to think they would share the same memory locations after the fork, but that’s not how it works!
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Exactly! The `fork()` creates a copy of the process, and consequently, it also allocates new memory for the child. Hence, each process may have the same logical structure, but the memory addresses are different. It's important to remember that every variable has its own stack frame in each process! Keep digging into these concepts!
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You're on point! The `fork()` function indeed creates a complete copy of the parent's address space for the child, leading to different addresses for the same variables. Even if both processes have the same initial values, their memory is physically distinct. This allows them to operate independently without affecting each other.
BrainyTech_56: That clears things up! Thanks! So basically, even though they look the same in code, their memory is isolated.
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You hit the nail on the head! After a `fork()`, the child process gets a new stack, so their variable addresses inevitably differ. Just remember, the child has its own memory space, which is crucial for process isolation! Exploring this concept is a great way to deepen your understanding of operating systems.
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CodeWhiz_77: Got it! So, if they have separate stacks, that makes total sense. Just one more question, what happens if the child modifies a variable after forking?