Question

Write the syntax to set the size of the runtime stack to 2048 bytes.

For Assembly Language

Answer 1

First let's know what these terms:

Base Address of Stack: The address from where Stack starts allocating memory.

Stack Pointer Register(%rsp): It is the processor register that points to the top element of the stack which means it contains the top element memory address.

The runtime stack allocates memory not in an incrementing fashion of memory addresses but in a decrementing way of memory addresses.

Eg: If currently the stack pointer (%rsp) is 48 and if memory is to be allocated to a double then it is we have to decrease 8 from the stack pointer but not to add 8 more to it. This is because the stack grows downwards the memory addresses not upwards.

Syntax to set the size of the runtime stack to 2048 bytes (x86_64)

movq $2048, %rsp

Syntax to allocate $2048 extra bytes to runtime stack (x86_64)

subq $2048, %rsp

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