初始化局部变量的值在C中的堆栈之前存储在哪里？

Question

I have a question about local variables. I am well aware that during a function call, the memory for the variable is allocated and after returning from the function, the memory is freed up. But from where does the program know what value to use during initialization?

void foo()
{
  uint8_t x = 2u;
}

So my question is, where is the value 2 stored in the memory before calling the function? My guess that it is in the text segment (in the non volatile memory) and is read from there to stack.

Thank you for the answers.

Answer 1

The compiler gets to decide.

The value may not even be "stored" anywhere: for some constants (eg zero) it's easier to just emit code to compute the value on demand rather than copy it from anywhere.

Answer 2

It's up to the compiler, of course, but whatever it is, it's going to be more or less the same as if you'd assigned a value to the variable within the expression. That is, if you say

void foo()
{
    uint8_t x = 2u;
}

it's just as if you'd said

void foo()
{
    uint8_t x;    /* uninitialized */
    x = 2u;
}