Msg/ClobberedSP

A function should always ensure that the stack pointer is the same at the entry and exit of the function. This message tells you that this didn't happen: the stack pointer was different at the function return than when the function was first called.

Examples

ARMv7

.global _start
_start:
    mov sp, #0x1000		// Initialize SP to something sane
    bl MyFunction
    nop
    nop
    # ...
    
MyFunction:
    push {r4}	// Change SP
    bx lr		// SP is different at return

Nios II

.global _start
_start:
    movi sp, 0x1000		# Initialize SP
    call Function
    nop
    nop
    
Function:
    subi sp, sp, 4		# Modify SP
    ret					# SP is different at return

Debugging

• Fundamentally, this message is complaining that the stack pointer differs between the start of the function and at the function return. Use breakpoints and make a note of the value of the stack pointer at both the function entry and return. Are they the same?
• The most common way to use the stack pointer is to modify it while pushing and popping values on the stack. When pushes and pops are mismatched, there is a net change in the stack pointer in the function.

Disabling this message

This debugging check can be disabled in the Debugging Checks section of the Settings box: Function clobbered ra or sp.