Enum MachDebugTagPos 

pub enum MachDebugTagPos {
    Post,
    Pre,
}

Debug tag position on an instruction.

We need to distinguish position on an instruction, and not just use offsets, because of the following case:

<tag1, tag2> call ...
<tag3, tag4> trapping_store ...

If the stack is walked and interpreted with debug tags while within the call, the PC seen will be the return point, i.e. the address after the call. If the stack is walked and interpreted with debug tags upon a trap of the following instruction, it will be the PC of that instruction – which is the same PC! Thus to disambiguate which tags we want, we attach a “pre/post” flag to every group of tags at an offset; and when we look up tags, we look them up for an offset and “position” at that offset.

Thus there are logically two positions at every offset – so the above will be emitted as

0: call ...
                         4, post: <tag1, tag2>
                         4, pre: <tag3, tag4>
4: trapping_store ...

Variants

Post

Tags attached after the instruction that ends at this offset.

This is used to attach tags to a call, because the PC we see when walking the stack is the return point.

Pre

Tags attached before the instruction that starts at this offset.

This is used to attach tags to every other kind of instruction, because the PC we see when processing a trap of that instruction is the PC of that instruction, not the following one.

Trait Implementations

impl Clone for MachDebugTagPos

fn clone(&self) -> MachDebugTagPos

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MachDebugTagPos

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for MachDebugTagPos

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for MachDebugTagPos

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl Serialize for MachDebugTagPos

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for MachDebugTagPos

impl Eq for MachDebugTagPos

impl StructuralPartialEq for MachDebugTagPos