Enum framehop::FrameAddress

pub enum FrameAddress {
    InstructionPointer(u64),
    ReturnAddress(NonZeroU64),
}

An absolute code address for a stack frame. Can either be taken directly from the instruction pointer (“program counter”), or from a return address.

These addresses are “AVMAs”, i.e. Actual Virtual Memory Addresses, i.e. addresses in the virtual memory of the profiled process.

Variants

InstructionPointer(u64)

This address is the instruction pointer / program counter. This is what unwinding starts with.

ReturnAddress(NonZeroU64)

This is a return address, i.e. the address to which the CPU will jump to when returning from a function. This is the address of the instruction after the call instruction.

Unwinding produces a list of return addresses.

Implementations

impl FrameAddress

pub fn from_instruction_pointer(ip: u64) -> Self

Create a FrameAddress::InstructionPointer.

pub fn from_return_address(return_address: u64) -> Option<Self>

Create a FrameAddress::ReturnAddress. This returns None if the given address is zero.

pub fn address(self) -> u64

The raw address (AVMA).

pub fn address_for_lookup(self) -> u64

The address (AVMA) that should be used for lookup.

If this address is taken directly from the instruction pointer, then the lookup address is just the raw address.

If this address is a return address, then the lookup address is that address minus one byte. This adjusted address will point inside the call instruction. This subtraction of one byte is needed if you want to look up unwind information or debug information, because you usually want the information for the call, not for the next instruction after the call.

Furthermore, this distinction matters if a function calls a noreturn function as the last thing it does: If the call is the final instruction of the function, then the return address will point after the function, into the next function. If, during unwinding, you look up unwind information for that next function, you’d get incorrect unwinding. This has been observed in practice with +[NSThread exit].

pub fn is_return_address(self) -> bool

Returns whether this address is a return address.

Trait Implementations

impl Clone for FrameAddress

fn clone(&self) -> FrameAddress

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FrameAddress

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for FrameAddress

fn eq(&self, other: &FrameAddress) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for FrameAddress

impl Eq for FrameAddress

impl StructuralEq for FrameAddress

impl StructuralPartialEq for FrameAddress