Msg/ClobberedSP - Revision history

Henry at 03:55, 17 March 2019

2019-03-17T03:55:56Z

@@ Line 31: / Line 31: @@
      subi sp, sp, 4			# Modify SP
      ret					# SP is different at return
 </syntaxhighlight>

2019-03-10T09:54:59Z

← Older revision		Revision as of 09:54, 10 March 2019
Line 1:		Line 1:
	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.		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.

	If you clobbered ra, see also [[Msg/ClobberedRA]]		If you also clobbered ra, see also [[Msg/ClobberedRA]]

	=== Examples ===		=== Examples ===

2019-03-10T07:40:15Z

← Older revision		Revision as of 07:40, 10 March 2019
Line 1:		Line 1:
	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.		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.

			If you clobbered ra, see also [[Msg/ClobberedRA]]

	=== Examples ===		=== Examples ===

2019-03-10T07:27:26Z

Debugging

← Older revision		Revision as of 07:27, 10 March 2019
Line 34:		Line 34:
	* 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?		* 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.		* 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.
			* The two places where stack pointer manipulations often occur are at the function prologue and epilogue, and allocating and deallocating arguments passed on the stack when calling a function. These operations are all matched. If your function modifies the stack pointer for other purposes, change your code so that this doesn't happen (e.g., copy the stack pointer to another register and modify that, instead of modifying the stack pointer).

	=== Implementation ===		=== Implementation ===

2019-03-10T07:09:36Z

Examples

← Older revision		Revision as of 07:09, 10 March 2019
Line 14:		Line 14:

	MyFunction:		MyFunction:
	push {r4} // Change SP		push {r4} // Change SP
	bx lr // SP is different at return		bx lr // SP is different at return
	</syntaxhighlight>		</syntaxhighlight>
	==== Nios II ====		==== Nios II ====
Line 27:		Line 27:

	Function:		Function:
	subi sp, sp, 4 # Modify SP		subi sp, sp, 4 # Modify SP
	ret # SP is different at return		ret # SP is different at return
	</syntaxhighlight>		</syntaxhighlight>

2019-03-10T07:08:59Z

← Older revision		Revision as of 07:08, 10 March 2019
Line 32:		Line 32:

	=== Debugging ===		=== 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?		* 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.		* 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.

2019-03-10T06:09:34Z

← Older revision		Revision as of 06:09, 10 March 2019
Line 38:		Line 38:
	The simulator identifies idiomatic call and return instructions executed at runtime. It records the values of registers when executing call instructions, and verifies that they haven't changed when executing the matching function return. This warning is generated at the return instruction.		The simulator identifies idiomatic call and return instructions executed at runtime. It records the values of registers when executing call instructions, and verifies that they haven't changed when executing the matching function return. This warning is generated at the return instruction.

	{{DisableMsg\|Function clobbered ra or sp}}		{{DisableMsg\|Function clobbered ra or sp}}

			ARMv7: <b>Function clobbered sp, or bad return</b>

2019-03-10T04:46:54Z

← Older revision		Revision as of 04:46, 10 March 2019
Line 14:		Line 14:

	MyFunction:		MyFunction:
	push {r4} // Change SP		push {r4} // Change SP
	bx lr // SP is different at return		bx lr // SP is different at return
	</syntaxhighlight>		</syntaxhighlight>
	==== Nios II ====		==== Nios II ====

2019-03-10T04:23:36Z

← Older revision		Revision as of 04:23, 10 March 2019
Line 18:		Line 18:
	</syntaxhighlight>		</syntaxhighlight>
	==== Nios II ====		==== Nios II ====
	<syntaxhighlight lang="Asm" highlight="10">		<syntaxhighlight lang="Asm" line highlight="10">
	.global _start		.global _start
	_start:		_start:

2019-03-10T04:23:30Z

← Older revision		Revision as of 04:23, 10 March 2019
Line 4:		Line 4:
	==== ARMv7 ====		==== ARMv7 ====

	<syntaxhighlight lang="Asm" highlight="11">		<syntaxhighlight lang="Asm" line highlight="11">
	.global _start		.global _start
	_start:		_start: