Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 1729 insertions, 0 deletions

diff --git a/vendor/addr2line/src/lib.rs b/vendor/addr2line/src/lib.rs
new file mode 100644
index 0000000..3270aad
--- /dev/null
+++ b/vendor/addr2line/src/lib.rs
@@ -0,0 +1,1729 @@
+//! This crate provides a cross-platform library and binary for translating addresses into
+//! function names, file names and line numbers. Given an address in an executable or an
+//! offset in a section of a relocatable object, it uses the debugging information to
+//! figure out which file name and line number are associated with it.
+//!
+//! When used as a library, files must first be loaded using the
+//! [`object`](https://github.com/gimli-rs/object) crate.
+//! A context can then be created with [`Context::new`](./struct.Context.html#method.new).
+//! The context caches some of the parsed information so that multiple lookups are
+//! efficient.
+//! Location information is obtained with
+//! [`Context::find_location`](./struct.Context.html#method.find_location) or
+//! [`Context::find_location_range`](./struct.Context.html#method.find_location_range).
+//! Function information is obtained with
+//! [`Context::find_frames`](./struct.Context.html#method.find_frames), which returns
+//! a frame for each inline function. Each frame contains both name and location.
+//!
+//! The crate has an example CLI wrapper around the library which provides some of
+//! the functionality of the `addr2line` command line tool distributed with [GNU
+//! binutils](https://www.gnu.org/software/binutils/).
+//!
+//! Currently this library only provides information from the DWARF debugging information,
+//! which is parsed using [`gimli`](https://github.com/gimli-rs/gimli).  The example CLI
+//! wrapper also uses symbol table information provided by the `object` crate.
+#![deny(missing_docs)]
+#![no_std]
+
+#[cfg(feature = "std")]
+extern crate std;
+
+#[allow(unused_imports)]
+#[macro_use]
+extern crate alloc;
+
+#[cfg(feature = "fallible-iterator")]
+pub extern crate fallible_iterator;
+pub extern crate gimli;
+#[cfg(feature = "object")]
+pub extern crate object;
+
+use alloc::borrow::Cow;
+use alloc::boxed::Box;
+#[cfg(feature = "object")]
+use alloc::rc::Rc;
+use alloc::string::{String, ToString};
+use alloc::sync::Arc;
+use alloc::vec::Vec;
+
+use core::cmp::{self, Ordering};
+use core::iter;
+use core::marker::PhantomData;
+use core::mem;
+use core::num::NonZeroU64;
+use core::ops::ControlFlow;
+use core::u64;
+
+use crate::function::{Function, Functions, InlinedFunction};
+use crate::lazy::LazyCell;
+
+#[cfg(feature = "smallvec")]
+mod maybe_small {
+    pub type Vec<T> = smallvec::SmallVec<[T; 16]>;
+    pub type IntoIter<T> = smallvec::IntoIter<[T; 16]>;
+}
+#[cfg(not(feature = "smallvec"))]
+mod maybe_small {
+    pub type Vec<T> = alloc::vec::Vec<T>;
+    pub type IntoIter<T> = alloc::vec::IntoIter<T>;
+}
+
+#[cfg(all(feature = "std", feature = "object", feature = "memmap2"))]
+/// A simple builtin split DWARF loader.
+pub mod builtin_split_dwarf_loader;
+mod function;
+mod lazy;
+
+type Error = gimli::Error;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum DebugFile {
+    Primary,
+    Supplementary,
+    Dwo,
+}
+
+/// Operations that consult debug information may require additional files
+/// to be loaded if split DWARF is being used. This enum returns the result
+/// of the operation in the `Break` variant, or information about the split
+/// DWARF that is required and a continuation to invoke once it is available
+/// in the `Continue` variant.
+///
+/// This enum is intended to be used in a loop like so:
+/// ```no_run
+///   # use addr2line::*;
+///   # use std::sync::Arc;
+///   # let ctx: Context<gimli::EndianRcSlice<gimli::RunTimeEndian>> = todo!();
+///   # let do_split_dwarf_load = |load: SplitDwarfLoad<gimli::EndianRcSlice<gimli::RunTimeEndian>>| -> Option<Arc<gimli::Dwarf<gimli::EndianRcSlice<gimli::RunTimeEndian>>>> { None };
+///   const ADDRESS: u64 = 0xdeadbeef;
+///   let mut r = ctx.find_frames(ADDRESS);
+///   let result = loop {
+///     match r {
+///       LookupResult::Output(result) => break result,
+///       LookupResult::Load { load, continuation } => {
+///         let dwo = do_split_dwarf_load(load);
+///         r = continuation.resume(dwo);
+///       }
+///     }
+///   };
+/// ```
+pub enum LookupResult<L: LookupContinuation> {
+    /// The lookup requires split DWARF data to be loaded.
+    Load {
+        /// The information needed to find the split DWARF data.
+        load: SplitDwarfLoad<<L as LookupContinuation>::Buf>,
+        /// The continuation to resume with the loaded split DWARF data.
+        continuation: L,
+    },
+    /// The lookup has completed and produced an output.
+    Output(<L as LookupContinuation>::Output),
+}
+
+/// This trait represents a partially complete operation that can be resumed
+/// once a load of needed split DWARF data is completed or abandoned by the
+/// API consumer.
+pub trait LookupContinuation: Sized {
+    /// The final output of this operation.
+    type Output;
+    /// The type of reader used.
+    type Buf: gimli::Reader;
+
+    /// Resumes the operation with the provided data.
+    ///
+    /// After the caller loads the split DWARF data required, call this
+    /// method to resume the operation. The return value of this method
+    /// indicates if the computation has completed or if further data is
+    /// required.
+    ///
+    /// If the additional data cannot be located, or the caller does not
+    /// support split DWARF, `resume(None)` can be used to continue the
+    /// operation with the data that is available.
+    fn resume(self, input: Option<Arc<gimli::Dwarf<Self::Buf>>>) -> LookupResult<Self>;
+}
+
+impl<L: LookupContinuation> LookupResult<L> {
+    /// Callers that do not handle split DWARF can call `skip_all_loads`
+    /// to fast-forward to the end result. This result is produced with
+    /// the data that is available and may be less accurate than the
+    /// the results that would be produced if the caller did properly
+    /// support split DWARF.
+    pub fn skip_all_loads(mut self) -> L::Output {
+        loop {
+            self = match self {
+                LookupResult::Output(t) => return t,
+                LookupResult::Load { continuation, .. } => continuation.resume(None),
+            };
+        }
+    }
+
+    fn map<T, F: FnOnce(L::Output) -> T>(self, f: F) -> LookupResult<MappedLookup<T, L, F>> {
+        match self {
+            LookupResult::Output(t) => LookupResult::Output(f(t)),
+            LookupResult::Load { load, continuation } => LookupResult::Load {
+                load,
+                continuation: MappedLookup {
+                    original: continuation,
+                    mutator: f,
+                },
+            },
+        }
+    }
+
+    fn unwrap(self) -> L::Output {
+        match self {
+            LookupResult::Output(t) => t,
+            LookupResult::Load { .. } => unreachable!("Internal API misuse"),
+        }
+    }
+}
+
+/// The state necessary to perform address to line translation.
+///
+/// Constructing a `Context` is somewhat costly, so users should aim to reuse `Context`s
+/// when performing lookups for many addresses in the same executable.
+pub struct Context<R: gimli::Reader> {
+    sections: Arc<gimli::Dwarf<R>>,
+    unit_ranges: Box<[UnitRange]>,
+    units: Box<[ResUnit<R>]>,
+    sup_units: Box<[SupUnit<R>]>,
+}
+
+/// The type of `Context` that supports the `new` method.
+#[cfg(feature = "std-object")]
+pub type ObjectContext = Context<gimli::EndianRcSlice<gimli::RunTimeEndian>>;
+
+#[cfg(feature = "std-object")]
+impl Context<gimli::EndianRcSlice<gimli::RunTimeEndian>> {
+    /// Construct a new `Context`.
+    ///
+    /// The resulting `Context` uses `gimli::EndianRcSlice<gimli::RunTimeEndian>`.
+    /// This means it is not thread safe, has no lifetime constraints (since it copies
+    /// the input data), and works for any endianity.
+    ///
+    /// Performance sensitive applications may want to use `Context::from_dwarf`
+    /// with a more specialised `gimli::Reader` implementation.
+    #[inline]
+    pub fn new<'data: 'file, 'file, O: object::Object<'data, 'file>>(
+        file: &'file O,
+    ) -> Result<Self, Error> {
+        Self::new_with_sup(file, None)
+    }
+
+    /// Construct a new `Context`.
+    ///
+    /// Optionally also use a supplementary object file.
+    ///
+    /// The resulting `Context` uses `gimli::EndianRcSlice<gimli::RunTimeEndian>`.
+    /// This means it is not thread safe, has no lifetime constraints (since it copies
+    /// the input data), and works for any endianity.
+    ///
+    /// Performance sensitive applications may want to use `Context::from_dwarf`
+    /// with a more specialised `gimli::Reader` implementation.
+    pub fn new_with_sup<'data: 'file, 'file, O: object::Object<'data, 'file>>(
+        file: &'file O,
+        sup_file: Option<&'file O>,
+    ) -> Result<Self, Error> {
+        let endian = if file.is_little_endian() {
+            gimli::RunTimeEndian::Little
+        } else {
+            gimli::RunTimeEndian::Big
+        };
+
+        fn load_section<'data: 'file, 'file, O, Endian>(
+            id: gimli::SectionId,
+            file: &'file O,
+            endian: Endian,
+        ) -> Result<gimli::EndianRcSlice<Endian>, Error>
+        where
+            O: object::Object<'data, 'file>,
+            Endian: gimli::Endianity,
+        {
+            use object::ObjectSection;
+
+            let data = file
+                .section_by_name(id.name())
+                .and_then(|section| section.uncompressed_data().ok())
+                .unwrap_or(Cow::Borrowed(&[]));
+            Ok(gimli::EndianRcSlice::new(Rc::from(&*data), endian))
+        }
+
+        let mut dwarf = gimli::Dwarf::load(|id| load_section(id, file, endian))?;
+        if let Some(sup_file) = sup_file {
+            dwarf.load_sup(|id| load_section(id, sup_file, endian))?;
+        }
+        Context::from_dwarf(dwarf)
+    }
+}
+
+impl<R: gimli::Reader> Context<R> {
+    /// Construct a new `Context` from DWARF sections.
+    ///
+    /// This method does not support using a supplementary object file.
+    pub fn from_sections(
+        debug_abbrev: gimli::DebugAbbrev<R>,
+        debug_addr: gimli::DebugAddr<R>,
+        debug_aranges: gimli::DebugAranges<R>,
+        debug_info: gimli::DebugInfo<R>,
+        debug_line: gimli::DebugLine<R>,
+        debug_line_str: gimli::DebugLineStr<R>,
+        debug_ranges: gimli::DebugRanges<R>,
+        debug_rnglists: gimli::DebugRngLists<R>,
+        debug_str: gimli::DebugStr<R>,
+        debug_str_offsets: gimli::DebugStrOffsets<R>,
+        default_section: R,
+    ) -> Result<Self, Error> {
+        Self::from_dwarf(gimli::Dwarf {
+            debug_abbrev,
+            debug_addr,
+            debug_aranges,
+            debug_info,
+            debug_line,
+            debug_line_str,
+            debug_str,
+            debug_str_offsets,
+            debug_types: default_section.clone().into(),
+            locations: gimli::LocationLists::new(
+                default_section.clone().into(),
+                default_section.into(),
+            ),
+            ranges: gimli::RangeLists::new(debug_ranges, debug_rnglists),
+            file_type: gimli::DwarfFileType::Main,
+            sup: None,
+            abbreviations_cache: gimli::AbbreviationsCache::new(),
+        })
+    }
+
+    /// Construct a new `Context` from an existing [`gimli::Dwarf`] object.
+    #[inline]
+    pub fn from_dwarf(sections: gimli::Dwarf<R>) -> Result<Context<R>, Error> {
+        let sections = Arc::new(sections);
+        let (unit_ranges, units) = Context::parse_units(&sections)?;
+        let sup_units = if let Some(sup) = sections.sup.as_ref() {
+            Context::parse_sup(sup)?
+        } else {
+            Vec::new()
+        };
+        Ok(Context {
+            sections,
+            unit_ranges: unit_ranges.into_boxed_slice(),
+            units: units.into_boxed_slice(),
+            sup_units: sup_units.into_boxed_slice(),
+        })
+    }
+
+    /// Finds the CUs for the function address given.
+    ///
+    /// There might be multiple CUs whose range contains this address.
+    /// Weak symbols have shown up in the wild which cause this to happen
+    /// but otherwise this can happen if the CU has non-contiguous functions
+    /// but only reports a single range.
+    ///
+    /// Consequently we return an iterator for all CUs which may contain the
+    /// address, and the caller must check if there is actually a function or
+    /// location in the CU for that address.
+    fn find_units(&self, probe: u64) -> impl Iterator<Item = &ResUnit<R>> {
+        self.find_units_range(probe, probe + 1)
+            .map(|(unit, _range)| unit)
+    }
+
+    /// Finds the CUs covering the range of addresses given.
+    ///
+    /// The range is [low, high) (ie, the upper bound is exclusive). This can return multiple
+    /// ranges for the same unit.
+    #[inline]
+    fn find_units_range(
+        &self,
+        probe_low: u64,
+        probe_high: u64,
+    ) -> impl Iterator<Item = (&ResUnit<R>, &gimli::Range)> {
+        // First up find the position in the array which could have our function
+        // address.
+        let pos = match self
+            .unit_ranges
+            .binary_search_by_key(&probe_high, |i| i.range.begin)
+        {
+            // Although unlikely, we could find an exact match.
+            Ok(i) => i + 1,
+            // No exact match was found, but this probe would fit at slot `i`.
+            // This means that slot `i` is bigger than `probe`, along with all
+            // indices greater than `i`, so we need to search all previous
+            // entries.
+            Err(i) => i,
+        };
+
+        // Once we have our index we iterate backwards from that position
+        // looking for a matching CU.
+        self.unit_ranges[..pos]
+            .iter()
+            .rev()
+            .take_while(move |i| {
+                // We know that this CU's start is beneath the probe already because
+                // of our sorted array.
+                debug_assert!(i.range.begin <= probe_high);
+
+                // Each entry keeps track of the maximum end address seen so far,
+                // starting from the beginning of the array of unit ranges. We're
+                // iterating in reverse so if our probe is beyond the maximum range
+                // of this entry, then it's guaranteed to not fit in any prior
+                // entries, so we break out.
+                probe_low < i.max_end
+            })
+            .filter_map(move |i| {
+                // If this CU doesn't actually contain this address, move to the
+                // next CU.
+                if probe_low >= i.range.end || probe_high <= i.range.begin {
+                    return None;
+                }
+                Some((&self.units[i.unit_id], &i.range))
+            })
+    }
+
+    /// Find the DWARF unit corresponding to the given virtual memory address.
+    pub fn find_dwarf_and_unit(
+        &self,
+        probe: u64,
+    ) -> LookupResult<
+        impl LookupContinuation<Output = Option<(&gimli::Dwarf<R>, &gimli::Unit<R>)>, Buf = R>,
+    > {
+        let mut units_iter = self.find_units(probe);
+        if let Some(unit) = units_iter.next() {
+            return LoopingLookup::new_lookup(
+                unit.find_function_or_location(probe, self),
+                move |r| {
+                    ControlFlow::Break(match r {
+                        Ok((Some(_), _)) | Ok((_, Some(_))) => {
+                            let (_file, sections, unit) = unit
+                                .dwarf_and_unit_dwo(self)
+                                // We've already been through both error cases here to get to this point.
+                                .unwrap()
+                                .unwrap();
+                            Some((sections, unit))
+                        }
+                        _ => match units_iter.next() {
+                            Some(next_unit) => {
+                                return ControlFlow::Continue(
+                                    next_unit.find_function_or_location(probe, self),
+                                );
+                            }
+                            None => None,
+                        },
+                    })
+                },
+            );
+        }
+
+        LoopingLookup::new_complete(None)
+    }
+
+    /// Find the source file and line corresponding to the given virtual memory address.
+    pub fn find_location(&self, probe: u64) -> Result<Option<Location<'_>>, Error> {
+        for unit in self.find_units(probe) {
+            if let Some(location) = unit.find_location(probe, &self.sections)? {
+                return Ok(Some(location));
+            }
+        }
+        Ok(None)
+    }
+
+    /// Return source file and lines for a range of addresses. For each location it also
+    /// returns the address and size of the range of the underlying instructions.
+    pub fn find_location_range(
+        &self,
+        probe_low: u64,
+        probe_high: u64,
+    ) -> Result<LocationRangeIter<'_, R>, Error> {
+        LocationRangeIter::new(self, probe_low, probe_high)
+    }
+
+    /// Return an iterator for the function frames corresponding to the given virtual
+    /// memory address.
+    ///
+    /// If the probe address is not for an inline function then only one frame is
+    /// returned.
+    ///
+    /// If the probe address is for an inline function then the first frame corresponds
+    /// to the innermost inline function.  Subsequent frames contain the caller and call
+    /// location, until an non-inline caller is reached.
+    pub fn find_frames(
+        &self,
+        probe: u64,
+    ) -> LookupResult<impl LookupContinuation<Output = Result<FrameIter<'_, R>, Error>, Buf = R>>
+    {
+        let mut units_iter = self.find_units(probe);
+        if let Some(unit) = units_iter.next() {
+            LoopingLookup::new_lookup(unit.find_function_or_location(probe, self), move |r| {
+                ControlFlow::Break(match r {
+                    Err(e) => Err(e),
+                    Ok((Some(function), location)) => {
+                        let inlined_functions = function.find_inlined_functions(probe);
+                        Ok(FrameIter(FrameIterState::Frames(FrameIterFrames {
+                            unit,
+                            sections: &self.sections,
+                            function,
+                            inlined_functions,
+                            next: location,
+                        })))
+                    }
+                    Ok((None, Some(location))) => {
+                        Ok(FrameIter(FrameIterState::Location(Some(location))))
+                    }
+                    Ok((None, None)) => match units_iter.next() {
+                        Some(next_unit) => {
+                            return ControlFlow::Continue(
+                                next_unit.find_function_or_location(probe, self),
+                            );
+                        }
+                        None => Ok(FrameIter(FrameIterState::Empty)),
+                    },
+                })
+            })
+        } else {
+            LoopingLookup::new_complete(Ok(FrameIter(FrameIterState::Empty)))
+        }
+    }
+
+    /// Preload units for `probe`.
+    ///
+    /// The iterator returns pairs of `SplitDwarfLoad`s containing the
+    /// information needed to locate and load split DWARF for `probe` and
+    /// a matching callback to invoke once that data is available.
+    ///
+    /// If this method is called, and all of the returned closures are invoked,
+    /// addr2line guarantees that any future API call for the address `probe`
+    /// will not require the loading of any split DWARF.
+    ///
+    /// ```no_run
+    ///   # use addr2line::*;
+    ///   # use std::sync::Arc;
+    ///   # let ctx: Context<gimli::EndianRcSlice<gimli::RunTimeEndian>> = todo!();
+    ///   # let do_split_dwarf_load = |load: SplitDwarfLoad<gimli::EndianRcSlice<gimli::RunTimeEndian>>| -> Option<Arc<gimli::Dwarf<gimli::EndianRcSlice<gimli::RunTimeEndian>>>> { None };
+    ///   const ADDRESS: u64 = 0xdeadbeef;
+    ///   ctx.preload_units(ADDRESS).for_each(|(load, callback)| {
+    ///     let dwo = do_split_dwarf_load(load);
+    ///     callback(dwo);
+    ///   });
+    ///
+    ///   let frames_iter = match ctx.find_frames(ADDRESS) {
+    ///     LookupResult::Output(result) => result,
+    ///     LookupResult::Load { .. } => unreachable!("addr2line promised we wouldn't get here"),
+    ///   };
+    ///
+    ///   // ...
+    /// ```
+    pub fn preload_units(
+        &'_ self,
+        probe: u64,
+    ) -> impl Iterator<
+        Item = (
+            SplitDwarfLoad<R>,
+            impl FnOnce(Option<Arc<gimli::Dwarf<R>>>) -> Result<(), gimli::Error> + '_,
+        ),
+    > {
+        self.find_units(probe)
+            .filter_map(move |unit| match unit.dwarf_and_unit_dwo(self) {
+                LookupResult::Output(_) => None,
+                LookupResult::Load { load, continuation } => Some((load, |result| {
+                    continuation.resume(result).unwrap().map(|_| ())
+                })),
+            })
+    }
+
+    /// Initialize all line data structures. This is used for benchmarks.
+    #[doc(hidden)]
+    pub fn parse_lines(&self) -> Result<(), Error> {
+        for unit in self.units.iter() {
+            unit.parse_lines(&self.sections)?;
+        }
+        Ok(())
+    }
+
+    /// Initialize all function data structures. This is used for benchmarks.
+    #[doc(hidden)]
+    pub fn parse_functions(&self) -> Result<(), Error> {
+        for unit in self.units.iter() {
+            unit.parse_functions(self).skip_all_loads()?;
+        }
+        Ok(())
+    }
+
+    /// Initialize all inlined function data structures. This is used for benchmarks.
+    #[doc(hidden)]
+    pub fn parse_inlined_functions(&self) -> Result<(), Error> {
+        for unit in self.units.iter() {
+            unit.parse_inlined_functions(self).skip_all_loads()?;
+        }
+        Ok(())
+    }
+}
+
+struct UnitRange {
+    unit_id: usize,
+    max_end: u64,
+    range: gimli::Range,
+}
+
+struct ResUnit<R: gimli::Reader> {
+    offset: gimli::DebugInfoOffset<R::Offset>,
+    dw_unit: gimli::Unit<R>,
+    lang: Option<gimli::DwLang>,
+    lines: LazyCell<Result<Lines, Error>>,
+    funcs: LazyCell<Result<Functions<R>, Error>>,
+    dwo: LazyCell<Result<Option<Box<(Arc<gimli::Dwarf<R>>, gimli::Unit<R>)>>, Error>>,
+}
+
+struct SupUnit<R: gimli::Reader> {
+    offset: gimli::DebugInfoOffset<R::Offset>,
+    dw_unit: gimli::Unit<R>,
+}
+
+impl<R: gimli::Reader> Context<R> {
+    fn parse_units(sections: &gimli::Dwarf<R>) -> Result<(Vec<UnitRange>, Vec<ResUnit<R>>), Error> {
+        // Find all the references to compilation units in .debug_aranges.
+        // Note that we always also iterate through all of .debug_info to
+        // find compilation units, because .debug_aranges may be missing some.
+        let mut aranges = Vec::new();
+        let mut headers = sections.debug_aranges.headers();
+        while let Some(header) = headers.next()? {
+            aranges.push((header.debug_info_offset(), header.offset()));
+        }
+        aranges.sort_by_key(|i| i.0);
+
+        let mut unit_ranges = Vec::new();
+        let mut res_units = Vec::new();
+        let mut units = sections.units();
+        while let Some(header) = units.next()? {
+            let unit_id = res_units.len();
+            let offset = match header.offset().as_debug_info_offset() {
+                Some(offset) => offset,
+                None => continue,
+            };
+            // We mainly want compile units, but we may need to follow references to entries
+            // within other units for function names.  We don't need anything from type units.
+            match header.type_() {
+                gimli::UnitType::Type { .. } | gimli::UnitType::SplitType { .. } => continue,
+                _ => {}
+            }
+            let dw_unit = match sections.unit(header) {
+                Ok(dw_unit) => dw_unit,
+                Err(_) => continue,
+            };
+
+            let mut lang = None;
+            let mut have_unit_range = false;
+            {
+                let mut entries = dw_unit.entries_raw(None)?;
+
+                let abbrev = match entries.read_abbreviation()? {
+                    Some(abbrev) => abbrev,
+                    None => continue,
+                };
+
+                let mut ranges = RangeAttributes::default();
+                for spec in abbrev.attributes() {
+                    let attr = entries.read_attribute(*spec)?;
+                    match attr.name() {
+                        gimli::DW_AT_low_pc => match attr.value() {
+                            gimli::AttributeValue::Addr(val) => ranges.low_pc = Some(val),
+                            gimli::AttributeValue::DebugAddrIndex(index) => {
+                                ranges.low_pc = Some(sections.address(&dw_unit, index)?);
+                            }
+                            _ => {}
+                        },
+                        gimli::DW_AT_high_pc => match attr.value() {
+                            gimli::AttributeValue::Addr(val) => ranges.high_pc = Some(val),
+                            gimli::AttributeValue::DebugAddrIndex(index) => {
+                                ranges.high_pc = Some(sections.address(&dw_unit, index)?);
+                            }
+                            gimli::AttributeValue::Udata(val) => ranges.size = Some(val),
+                            _ => {}
+                        },
+                        gimli::DW_AT_ranges => {
+                            ranges.ranges_offset =
+                                sections.attr_ranges_offset(&dw_unit, attr.value())?;
+                        }
+                        gimli::DW_AT_language => {
+                            if let gimli::AttributeValue::Language(val) = attr.value() {
+                                lang = Some(val);
+                            }
+                        }
+                        _ => {}
+                    }
+                }
+
+                // Find the address ranges for the CU, using in order of preference:
+                // - DW_AT_ranges
+                // - .debug_aranges
+                // - DW_AT_low_pc/DW_AT_high_pc
+                //
+                // Using DW_AT_ranges before .debug_aranges is possibly an arbitrary choice,
+                // but the feeling is that DW_AT_ranges is more likely to be reliable or complete
+                // if it is present.
+                //
+                // .debug_aranges must be used before DW_AT_low_pc/DW_AT_high_pc because
+                // it has been observed on macOS that DW_AT_ranges was not emitted even for
+                // discontiguous CUs.
+                let i = match ranges.ranges_offset {
+                    Some(_) => None,
+                    None => aranges.binary_search_by_key(&offset, |x| x.0).ok(),
+                };
+                if let Some(mut i) = i {
+                    // There should be only one set per CU, but in practice multiple
+                    // sets have been observed. This is probably a compiler bug, but
+                    // either way we need to handle it.
+                    while i > 0 && aranges[i - 1].0 == offset {
+                        i -= 1;
+                    }
+                    for (_, aranges_offset) in aranges[i..].iter().take_while(|x| x.0 == offset) {
+                        let aranges_header = sections.debug_aranges.header(*aranges_offset)?;
+                        let mut aranges = aranges_header.entries();
+                        while let Some(arange) = aranges.next()? {
+                            if arange.length() != 0 {
+                                unit_ranges.push(UnitRange {
+                                    range: arange.range(),
+                                    unit_id,
+                                    max_end: 0,
+                                });
+                                have_unit_range = true;
+                            }
+                        }
+                    }
+                } else {
+                    have_unit_range |= ranges.for_each_range(sections, &dw_unit, |range| {
+                        unit_ranges.push(UnitRange {
+                            range,
+                            unit_id,
+                            max_end: 0,
+                        });
+                    })?;
+                }
+            }
+
+            let lines = LazyCell::new();
+            if !have_unit_range {
+                // The unit did not declare any ranges.
+                // Try to get some ranges from the line program sequences.
+                if let Some(ref ilnp) = dw_unit.line_program {
+                    if let Ok(lines) = lines
+                        .borrow_with(|| Lines::parse(&dw_unit, ilnp.clone(), sections))
+                        .as_ref()
+                    {
+                        for sequence in lines.sequences.iter() {
+                            unit_ranges.push(UnitRange {
+                                range: gimli::Range {
+                                    begin: sequence.start,
+                                    end: sequence.end,
+                                },
+                                unit_id,
+                                max_end: 0,
+                            })
+                        }
+                    }
+                }
+            }
+
+            res_units.push(ResUnit {
+                offset,
+                dw_unit,
+                lang,
+                lines,
+                funcs: LazyCell::new(),
+                dwo: LazyCell::new(),
+            });
+        }
+
+        // Sort this for faster lookup in `find_unit_and_address` below.
+        unit_ranges.sort_by_key(|i| i.range.begin);
+
+        // Calculate the `max_end` field now that we've determined the order of
+        // CUs.
+        let mut max = 0;
+        for i in unit_ranges.iter_mut() {
+            max = max.max(i.range.end);
+            i.max_end = max;
+        }
+
+        Ok((unit_ranges, res_units))
+    }
+
+    fn parse_sup(sections: &gimli::Dwarf<R>) -> Result<Vec<SupUnit<R>>, Error> {
+        let mut sup_units = Vec::new();
+        let mut units = sections.units();
+        while let Some(header) = units.next()? {
+            let offset = match header.offset().as_debug_info_offset() {
+                Some(offset) => offset,
+                None => continue,
+            };
+            let dw_unit = match sections.unit(header) {
+                Ok(dw_unit) => dw_unit,
+                Err(_) => continue,
+            };
+            sup_units.push(SupUnit { dw_unit, offset });
+        }
+        Ok(sup_units)
+    }
+
+    // Find the unit containing the given offset, and convert the offset into a unit offset.
+    fn find_unit(
+        &self,
+        offset: gimli::DebugInfoOffset<R::Offset>,
+        file: DebugFile,
+    ) -> Result<(&gimli::Unit<R>, gimli::UnitOffset<R::Offset>), Error> {
+        let unit = match file {
+            DebugFile::Primary => {
+                match self
+                    .units
+                    .binary_search_by_key(&offset.0, |unit| unit.offset.0)
+                {
+                    // There is never a DIE at the unit offset or before the first unit.
+                    Ok(_) | Err(0) => return Err(gimli::Error::NoEntryAtGivenOffset),
+                    Err(i) => &self.units[i - 1].dw_unit,
+                }
+            }
+            DebugFile::Supplementary => {
+                match self
+                    .sup_units
+                    .binary_search_by_key(&offset.0, |unit| unit.offset.0)
+                {
+                    // There is never a DIE at the unit offset or before the first unit.
+                    Ok(_) | Err(0) => return Err(gimli::Error::NoEntryAtGivenOffset),
+                    Err(i) => &self.sup_units[i - 1].dw_unit,
+                }
+            }
+            DebugFile::Dwo => return Err(gimli::Error::NoEntryAtGivenOffset),
+        };
+
+        let unit_offset = offset
+            .to_unit_offset(&unit.header)
+            .ok_or(gimli::Error::NoEntryAtGivenOffset)?;
+        Ok((unit, unit_offset))
+    }
+}
+
+struct Lines {
+    files: Box<[String]>,
+    sequences: Box<[LineSequence]>,
+}
+
+impl Lines {
+    fn parse<R: gimli::Reader>(
+        dw_unit: &gimli::Unit<R>,
+        ilnp: gimli::IncompleteLineProgram<R, R::Offset>,
+        sections: &gimli::Dwarf<R>,
+    ) -> Result<Self, Error> {
+        let mut sequences = Vec::new();
+        let mut sequence_rows = Vec::<LineRow>::new();
+        let mut rows = ilnp.rows();
+        while let Some((_, row)) = rows.next_row()? {
+            if row.end_sequence() {
+                if let Some(start) = sequence_rows.first().map(|x| x.address) {
+                    let end = row.address();
+                    let mut rows = Vec::new();
+                    mem::swap(&mut rows, &mut sequence_rows);
+                    sequences.push(LineSequence {
+                        start,
+                        end,
+                        rows: rows.into_boxed_slice(),
+                    });
+                }
+                continue;
+            }
+
+            let address = row.address();
+            let file_index = row.file_index();
+            let line = row.line().map(NonZeroU64::get).unwrap_or(0) as u32;
+            let column = match row.column() {
+                gimli::ColumnType::LeftEdge => 0,
+                gimli::ColumnType::Column(x) => x.get() as u32,
+            };
+
+            if let Some(last_row) = sequence_rows.last_mut() {
+                if last_row.address == address {
+                    last_row.file_index = file_index;
+                    last_row.line = line;
+                    last_row.column = column;
+                    continue;
+                }
+            }
+
+            sequence_rows.push(LineRow {
+                address,
+                file_index,
+                line,
+                column,
+            });
+        }
+        sequences.sort_by_key(|x| x.start);
+
+        let mut files = Vec::new();
+        let header = rows.header();
+        match header.file(0) {
+            Some(file) => files.push(render_file(dw_unit, file, header, sections)?),
+            None => files.push(String::from("")), // DWARF version <= 4 may not have 0th index
+        }
+        let mut index = 1;
+        while let Some(file) = header.file(index) {
+            files.push(render_file(dw_unit, file, header, sections)?);
+            index += 1;
+        }
+
+        Ok(Self {
+            files: files.into_boxed_slice(),
+            sequences: sequences.into_boxed_slice(),
+        })
+    }
+}
+
+fn render_file<R: gimli::Reader>(
+    dw_unit: &gimli::Unit<R>,
+    file: &gimli::FileEntry<R, R::Offset>,
+    header: &gimli::LineProgramHeader<R, R::Offset>,
+    sections: &gimli::Dwarf<R>,
+) -> Result<String, gimli::Error> {
+    let mut path = if let Some(ref comp_dir) = dw_unit.comp_dir {
+        comp_dir.to_string_lossy()?.into_owned()
+    } else {
+        String::new()
+    };
+
+    // The directory index 0 is defined to correspond to the compilation unit directory.
+    if file.directory_index() != 0 {
+        if let Some(directory) = file.directory(header) {
+            path_push(
+                &mut path,
+                sections
+                    .attr_string(dw_unit, directory)?
+                    .to_string_lossy()?
+                    .as_ref(),
+            );
+        }
+    }
+
+    path_push(
+        &mut path,
+        sections
+            .attr_string(dw_unit, file.path_name())?
+            .to_string_lossy()?
+            .as_ref(),
+    );
+
+    Ok(path)
+}
+
+struct LineSequence {
+    start: u64,
+    end: u64,
+    rows: Box<[LineRow]>,
+}
+
+struct LineRow {
+    address: u64,
+    file_index: u64,
+    line: u32,
+    column: u32,
+}
+
+/// This struct contains the information needed to find split DWARF data
+/// and to produce a `gimli::Dwarf<R>` for it.
+pub struct SplitDwarfLoad<R> {
+    /// The dwo id, for looking up in a DWARF package, or for
+    /// verifying an unpacked dwo found on the file system
+    pub dwo_id: gimli::DwoId,
+    /// The compilation directory `path` is relative to.
+    pub comp_dir: Option<R>,
+    /// A path on the filesystem, relative to `comp_dir` to find this dwo.
+    pub path: Option<R>,
+    /// Once the split DWARF data is loaded, the loader is expected
+    /// to call [make_dwo(parent)](gimli::read::Dwarf::make_dwo) before
+    /// returning the data.
+    pub parent: Arc<gimli::Dwarf<R>>,
+}
+
+struct SimpleLookup<T, R, F>
+where
+    F: FnOnce(Option<Arc<gimli::Dwarf<R>>>) -> T,
+    R: gimli::Reader,
+{
+    f: F,
+    phantom: PhantomData<(T, R)>,
+}
+
+impl<T, R, F> SimpleLookup<T, R, F>
+where
+    F: FnOnce(Option<Arc<gimli::Dwarf<R>>>) -> T,
+    R: gimli::Reader,
+{
+    fn new_complete(t: F::Output) -> LookupResult<SimpleLookup<T, R, F>> {
+        LookupResult::Output(t)
+    }
+
+    fn new_needs_load(load: SplitDwarfLoad<R>, f: F) -> LookupResult<SimpleLookup<T, R, F>> {
+        LookupResult::Load {
+            load,
+            continuation: SimpleLookup {
+                f,
+                phantom: PhantomData,
+            },
+        }
+    }
+}
+
+impl<T, R, F> LookupContinuation for SimpleLookup<T, R, F>
+where
+    F: FnOnce(Option<Arc<gimli::Dwarf<R>>>) -> T,
+    R: gimli::Reader,
+{
+    type Output = T;
+    type Buf = R;
+
+    fn resume(self, v: Option<Arc<gimli::Dwarf<Self::Buf>>>) -> LookupResult<Self> {
+        LookupResult::Output((self.f)(v))
+    }
+}
+
+struct MappedLookup<T, L, F>
+where
+    L: LookupContinuation,
+    F: FnOnce(L::Output) -> T,
+{
+    original: L,
+    mutator: F,
+}
+
+impl<T, L, F> LookupContinuation for MappedLookup<T, L, F>
+where
+    L: LookupContinuation,
+    F: FnOnce(L::Output) -> T,
+{
+    type Output = T;
+    type Buf = L::Buf;
+
+    fn resume(self, v: Option<Arc<gimli::Dwarf<Self::Buf>>>) -> LookupResult<Self> {
+        match self.original.resume(v) {
+            LookupResult::Output(t) => LookupResult::Output((self.mutator)(t)),
+            LookupResult::Load { load, continuation } => LookupResult::Load {
+                load,
+                continuation: MappedLookup {
+                    original: continuation,
+                    mutator: self.mutator,
+                },
+            },
+        }
+    }
+}
+
+/// Some functions (e.g. `find_frames`) require considering multiple
+/// compilation units, each of which might require their own split DWARF
+/// lookup (and thus produce a continuation).
+///
+/// We store the underlying continuation here as well as a mutator function
+/// that will either a) decide that the result of this continuation is
+/// what is needed and mutate it to the final result or b) produce another
+/// `LookupResult`. `new_lookup` will in turn eagerly drive any non-continuation
+/// `LookupResult` with successive invocations of the mutator, until a new
+/// continuation or a final result is produced. And finally, the impl of
+/// `LookupContinuation::resume` will call `new_lookup` each time the
+/// computation is resumed.
+struct LoopingLookup<T, L, F>
+where
+    L: LookupContinuation,
+    F: FnMut(L::Output) -> ControlFlow<T, LookupResult<L>>,
+{
+    continuation: L,
+    mutator: F,
+}
+
+impl<T, L, F> LoopingLookup<T, L, F>
+where
+    L: LookupContinuation,
+    F: FnMut(L::Output) -> ControlFlow<T, LookupResult<L>>,
+{
+    fn new_complete(t: T) -> LookupResult<Self> {
+        LookupResult::Output(t)
+    }
+
+    fn new_lookup(mut r: LookupResult<L>, mut mutator: F) -> LookupResult<Self> {
+        // Drive the loop eagerly so that we only ever have to represent one state
+        // (the r == ControlFlow::Continue state) in LoopingLookup.
+        loop {
+            match r {
+                LookupResult::Output(l) => match mutator(l) {
+                    ControlFlow::Break(t) => return LookupResult::Output(t),
+                    ControlFlow::Continue(r2) => {
+                        r = r2;
+                    }
+                },
+                LookupResult::Load { load, continuation } => {
+                    return LookupResult::Load {
+                        load,
+                        continuation: LoopingLookup {
+                            continuation,
+                            mutator,
+                        },
+                    };
+                }
+            }
+        }
+    }
+}
+
+impl<T, L, F> LookupContinuation for LoopingLookup<T, L, F>
+where
+    L: LookupContinuation,
+    F: FnMut(L::Output) -> ControlFlow<T, LookupResult<L>>,
+{
+    type Output = T;
+    type Buf = L::Buf;
+
+    fn resume(self, v: Option<Arc<gimli::Dwarf<Self::Buf>>>) -> LookupResult<Self> {
+        let r = self.continuation.resume(v);
+        LoopingLookup::new_lookup(r, self.mutator)
+    }
+}
+
+impl<R: gimli::Reader> ResUnit<R> {
+    fn dwarf_and_unit_dwo<'unit, 'ctx: 'unit>(
+        &'unit self,
+        ctx: &'ctx Context<R>,
+    ) -> LookupResult<
+        SimpleLookup<
+            Result<(DebugFile, &'unit gimli::Dwarf<R>, &'unit gimli::Unit<R>), Error>,
+            R,
+            impl FnOnce(
+                Option<Arc<gimli::Dwarf<R>>>,
+            )
+                -> Result<(DebugFile, &'unit gimli::Dwarf<R>, &'unit gimli::Unit<R>), Error>,
+        >,
+    > {
+        loop {
+            break SimpleLookup::new_complete(match self.dwo.borrow() {
+                Some(Ok(Some(v))) => Ok((DebugFile::Dwo, &*v.0, &v.1)),
+                Some(Ok(None)) => Ok((DebugFile::Primary, &*ctx.sections, &self.dw_unit)),
+                Some(Err(e)) => Err(*e),
+                None => {
+                    let dwo_id = match self.dw_unit.dwo_id {
+                        None => {
+                            self.dwo.borrow_with(|| Ok(None));
+                            continue;
+                        }
+                        Some(dwo_id) => dwo_id,
+                    };
+
+                    let comp_dir = self.dw_unit.comp_dir.clone();
+
+                    let dwo_name = self.dw_unit.dwo_name().and_then(|s| {
+                        if let Some(s) = s {
+                            Ok(Some(ctx.sections.attr_string(&self.dw_unit, s)?))
+                        } else {
+                            Ok(None)
+                        }
+                    });
+
+                    let path = match dwo_name {
+                        Ok(v) => v,
+                        Err(e) => {
+                            self.dwo.borrow_with(|| Err(e));
+                            continue;
+                        }
+                    };
+
+                    let process_dwo = move |dwo_dwarf: Option<Arc<gimli::Dwarf<R>>>| {
+                        let dwo_dwarf = match dwo_dwarf {
+                            None => return Ok(None),
+                            Some(dwo_dwarf) => dwo_dwarf,
+                        };
+                        let mut dwo_units = dwo_dwarf.units();
+                        let dwo_header = match dwo_units.next()? {
+                            Some(dwo_header) => dwo_header,
+                            None => return Ok(None),
+                        };
+
+                        let mut dwo_unit = dwo_dwarf.unit(dwo_header)?;
+                        dwo_unit.copy_relocated_attributes(&self.dw_unit);
+                        Ok(Some(Box::new((dwo_dwarf, dwo_unit))))
+                    };
+
+                    return SimpleLookup::new_needs_load(
+                        SplitDwarfLoad {
+                            dwo_id,
+                            comp_dir,
+                            path,
+                            parent: ctx.sections.clone(),
+                        },
+                        move |dwo_dwarf| match self.dwo.borrow_with(|| process_dwo(dwo_dwarf)) {
+                            Ok(Some(v)) => Ok((DebugFile::Dwo, &*v.0, &v.1)),
+                            Ok(None) => Ok((DebugFile::Primary, &*ctx.sections, &self.dw_unit)),
+                            Err(e) => Err(*e),
+                        },
+                    );
+                }
+            });
+        }
+    }
+
+    fn parse_lines(&self, sections: &gimli::Dwarf<R>) -> Result<Option<&Lines>, Error> {
+        // NB: line information is always stored in the main debug file so this does not need
+        // to handle DWOs.
+        let ilnp = match self.dw_unit.line_program {
+            Some(ref ilnp) => ilnp,
+            None => return Ok(None),
+        };
+        self.lines
+            .borrow_with(|| Lines::parse(&self.dw_unit, ilnp.clone(), sections))
+            .as_ref()
+            .map(Some)
+            .map_err(Error::clone)
+    }
+
+    fn parse_functions_dwarf_and_unit(
+        &self,
+        unit: &gimli::Unit<R>,
+        sections: &gimli::Dwarf<R>,
+    ) -> Result<&Functions<R>, Error> {
+        self.funcs
+            .borrow_with(|| Functions::parse(unit, sections))
+            .as_ref()
+            .map_err(Error::clone)
+    }
+
+    fn parse_functions<'unit, 'ctx: 'unit>(
+        &'unit self,
+        ctx: &'ctx Context<R>,
+    ) -> LookupResult<impl LookupContinuation<Output = Result<&'unit Functions<R>, Error>, Buf = R>>
+    {
+        self.dwarf_and_unit_dwo(ctx).map(move |r| {
+            let (_file, sections, unit) = r?;
+            self.parse_functions_dwarf_and_unit(unit, sections)
+        })
+    }
+    fn parse_inlined_functions<'unit, 'ctx: 'unit>(
+        &'unit self,
+        ctx: &'ctx Context<R>,
+    ) -> LookupResult<impl LookupContinuation<Output = Result<(), Error>, Buf = R> + 'unit> {
+        self.dwarf_and_unit_dwo(ctx).map(move |r| {
+            let (file, sections, unit) = r?;
+            self.funcs
+                .borrow_with(|| Functions::parse(unit, sections))
+                .as_ref()
+                .map_err(Error::clone)?
+                .parse_inlined_functions(file, unit, ctx, sections)
+        })
+    }
+
+    fn find_location(
+        &self,
+        probe: u64,
+        sections: &gimli::Dwarf<R>,
+    ) -> Result<Option<Location<'_>>, Error> {
+        if let Some(mut iter) = LocationRangeUnitIter::new(self, sections, probe, probe + 1)? {
+            match iter.next() {
+                None => Ok(None),
+                Some((_addr, _len, loc)) => Ok(Some(loc)),
+            }
+        } else {
+            Ok(None)
+        }
+    }
+
+    #[inline]
+    fn find_location_range(
+        &self,
+        probe_low: u64,
+        probe_high: u64,
+        sections: &gimli::Dwarf<R>,
+    ) -> Result<Option<LocationRangeUnitIter<'_>>, Error> {
+        LocationRangeUnitIter::new(self, sections, probe_low, probe_high)
+    }
+
+    fn find_function_or_location<'unit, 'ctx: 'unit>(
+        &'unit self,
+        probe: u64,
+        ctx: &'ctx Context<R>,
+    ) -> LookupResult<
+        impl LookupContinuation<
+            Output = Result<(Option<&'unit Function<R>>, Option<Location<'unit>>), Error>,
+            Buf = R,
+        >,
+    > {
+        self.dwarf_and_unit_dwo(ctx).map(move |r| {
+            let (file, sections, unit) = r?;
+            let functions = self.parse_functions_dwarf_and_unit(unit, sections)?;
+            let function = match functions.find_address(probe) {
+                Some(address) => {
+                    let function_index = functions.addresses[address].function;
+                    let (offset, ref function) = functions.functions[function_index];
+                    Some(
+                        function
+                            .borrow_with(|| Function::parse(offset, file, unit, ctx, sections))
+                            .as_ref()
+                            .map_err(Error::clone)?,
+                    )
+                }
+                None => None,
+            };
+            let location = self.find_location(probe, sections)?;
+            Ok((function, location))
+        })
+    }
+}
+
+/// Iterator over `Location`s in a range of addresses, returned by `Context::find_location_range`.
+pub struct LocationRangeIter<'ctx, R: gimli::Reader> {
+    unit_iter: Box<dyn Iterator<Item = (&'ctx ResUnit<R>, &'ctx gimli::Range)> + 'ctx>,
+    iter: Option<LocationRangeUnitIter<'ctx>>,
+
+    probe_low: u64,
+    probe_high: u64,
+    sections: &'ctx gimli::Dwarf<R>,
+}
+
+impl<'ctx, R: gimli::Reader> LocationRangeIter<'ctx, R> {
+    #[inline]
+    fn new(ctx: &'ctx Context<R>, probe_low: u64, probe_high: u64) -> Result<Self, Error> {
+        let sections = &ctx.sections;
+        let unit_iter = ctx.find_units_range(probe_low, probe_high);
+        Ok(Self {
+            unit_iter: Box::new(unit_iter),
+            iter: None,
+            probe_low,
+            probe_high,
+            sections,
+        })
+    }
+
+    fn next_loc(&mut self) -> Result<Option<(u64, u64, Location<'ctx>)>, Error> {
+        loop {
+            let iter = self.iter.take();
+            match iter {
+                None => match self.unit_iter.next() {
+                    Some((unit, range)) => {
+                        self.iter = unit.find_location_range(
+                            cmp::max(self.probe_low, range.begin),
+                            cmp::min(self.probe_high, range.end),
+                            self.sections,
+                        )?;
+                    }
+                    None => return Ok(None),
+                },
+                Some(mut iter) => {
+                    if let item @ Some(_) = iter.next() {
+                        self.iter = Some(iter);
+                        return Ok(item);
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl<'ctx, R> Iterator for LocationRangeIter<'ctx, R>
+where
+    R: gimli::Reader + 'ctx,
+{
+    type Item = (u64, u64, Location<'ctx>);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.next_loc() {
+            Err(_) => None,
+            Ok(loc) => loc,
+        }
+    }
+}
+
+#[cfg(feature = "fallible-iterator")]
+impl<'ctx, R> fallible_iterator::FallibleIterator for LocationRangeIter<'ctx, R>
+where
+    R: gimli::Reader + 'ctx,
+{
+    type Item = (u64, u64, Location<'ctx>);
+    type Error = Error;
+
+    #[inline]
+    fn next(&mut self) -> Result<Option<Self::Item>, Self::Error> {
+        self.next_loc()
+    }
+}
+
+struct LocationRangeUnitIter<'ctx> {
+    lines: &'ctx Lines,
+    seqs: &'ctx [LineSequence],
+    seq_idx: usize,
+    row_idx: usize,
+    probe_high: u64,
+}
+
+impl<'ctx> LocationRangeUnitIter<'ctx> {
+    fn new<R: gimli::Reader>(
+        resunit: &'ctx ResUnit<R>,
+        sections: &gimli::Dwarf<R>,
+        probe_low: u64,
+        probe_high: u64,
+    ) -> Result<Option<Self>, Error> {
+        let lines = resunit.parse_lines(sections)?;
+
+        if let Some(lines) = lines {
+            // Find index for probe_low.
+            let seq_idx = lines.sequences.binary_search_by(|sequence| {
+                if probe_low < sequence.start {
+                    Ordering::Greater
+                } else if probe_low >= sequence.end {
+                    Ordering::Less
+                } else {
+                    Ordering::Equal
+                }
+            });
+            let seq_idx = match seq_idx {
+                Ok(x) => x,
+                Err(0) => 0, // probe below sequence, but range could overlap
+                Err(_) => lines.sequences.len(),
+            };
+
+            let row_idx = if let Some(seq) = lines.sequences.get(seq_idx) {
+                let idx = seq.rows.binary_search_by(|row| row.address.cmp(&probe_low));
+                match idx {
+                    Ok(x) => x,
+                    Err(0) => 0, // probe below sequence, but range could overlap
+                    Err(x) => x - 1,
+                }
+            } else {
+                0
+            };
+
+            Ok(Some(Self {
+                lines,
+                seqs: &*lines.sequences,
+                seq_idx,
+                row_idx,
+                probe_high,
+            }))
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+impl<'ctx> Iterator for LocationRangeUnitIter<'ctx> {
+    type Item = (u64, u64, Location<'ctx>);
+
+    fn next(&mut self) -> Option<(u64, u64, Location<'ctx>)> {
+        while let Some(seq) = self.seqs.get(self.seq_idx) {
+            if seq.start >= self.probe_high {
+                break;
+            }
+
+            match seq.rows.get(self.row_idx) {
+                Some(row) => {
+                    if row.address >= self.probe_high {
+                        break;
+                    }
+
+                    let file = self
+                        .lines
+                        .files
+                        .get(row.file_index as usize)
+                        .map(String::as_str);
+                    let nextaddr = seq
+                        .rows
+                        .get(self.row_idx + 1)
+                        .map(|row| row.address)
+                        .unwrap_or(seq.end);
+
+                    let item = (
+                        row.address,
+                        nextaddr - row.address,
+                        Location {
+                            file,
+                            line: if row.line != 0 { Some(row.line) } else { None },
+                            column: if row.column != 0 {
+                                Some(row.column)
+                            } else {
+                                None
+                            },
+                        },
+                    );
+                    self.row_idx += 1;
+
+                    return Some(item);
+                }
+                None => {
+                    self.seq_idx += 1;
+                    self.row_idx = 0;
+                }
+            }
+        }
+        None
+    }
+}
+
+fn path_push(path: &mut String, p: &str) {
+    if has_unix_root(p) || has_windows_root(p) {
+        *path = p.to_string();
+    } else {
+        let dir_separator = if has_windows_root(path.as_str()) {
+            '\\'
+        } else {
+            '/'
+        };
+
+        if !path.is_empty() && !path.ends_with(dir_separator) {
+            path.push(dir_separator);
+        }
+        *path += p;
+    }
+}
+
+/// Check if the path in the given string has a unix style root
+fn has_unix_root(p: &str) -> bool {
+    p.starts_with('/')
+}
+
+/// Check if the path in the given string has a windows style root
+fn has_windows_root(p: &str) -> bool {
+    p.starts_with('\\') || p.get(1..3) == Some(":\\")
+}
+struct RangeAttributes<R: gimli::Reader> {
+    low_pc: Option<u64>,
+    high_pc: Option<u64>,
+    size: Option<u64>,
+    ranges_offset: Option<gimli::RangeListsOffset<<R as gimli::Reader>::Offset>>,
+}
+
+impl<R: gimli::Reader> Default for RangeAttributes<R> {
+    fn default() -> Self {
+        RangeAttributes {
+            low_pc: None,
+            high_pc: None,
+            size: None,
+            ranges_offset: None,
+        }
+    }
+}
+
+impl<R: gimli::Reader> RangeAttributes<R> {
+    fn for_each_range<F: FnMut(gimli::Range)>(
+        &self,
+        sections: &gimli::Dwarf<R>,
+        unit: &gimli::Unit<R>,
+        mut f: F,
+    ) -> Result<bool, Error> {
+        let mut added_any = false;
+        let mut add_range = |range: gimli::Range| {
+            if range.begin < range.end {
+                f(range);
+                added_any = true
+            }
+        };
+        if let Some(ranges_offset) = self.ranges_offset {
+            let mut range_list = sections.ranges(unit, ranges_offset)?;
+            while let Some(range) = range_list.next()? {
+                add_range(range);
+            }
+        } else if let (Some(begin), Some(end)) = (self.low_pc, self.high_pc) {
+            add_range(gimli::Range { begin, end });
+        } else if let (Some(begin), Some(size)) = (self.low_pc, self.size) {
+            add_range(gimli::Range {
+                begin,
+                end: begin + size,
+            });
+        }
+        Ok(added_any)
+    }
+}
+
+/// An iterator over function frames.
+pub struct FrameIter<'ctx, R>(FrameIterState<'ctx, R>)
+where
+    R: gimli::Reader;
+
+enum FrameIterState<'ctx, R>
+where
+    R: gimli::Reader,
+{
+    Empty,
+    Location(Option<Location<'ctx>>),
+    Frames(FrameIterFrames<'ctx, R>),
+}
+
+struct FrameIterFrames<'ctx, R>
+where
+    R: gimli::Reader,
+{
+    unit: &'ctx ResUnit<R>,
+    sections: &'ctx gimli::Dwarf<R>,
+    function: &'ctx Function<R>,
+    inlined_functions: iter::Rev<maybe_small::IntoIter<&'ctx InlinedFunction<R>>>,
+    next: Option<Location<'ctx>>,
+}
+
+impl<'ctx, R> FrameIter<'ctx, R>
+where
+    R: gimli::Reader + 'ctx,
+{
+    /// Advances the iterator and returns the next frame.
+    pub fn next(&mut self) -> Result<Option<Frame<'ctx, R>>, Error> {
+        let frames = match &mut self.0 {
+            FrameIterState::Empty => return Ok(None),
+            FrameIterState::Location(location) => {
+                // We can't move out of a mutable reference, so use `take` instead.
+                let location = location.take();
+                self.0 = FrameIterState::Empty;
+                return Ok(Some(Frame {
+                    dw_die_offset: None,
+                    function: None,
+                    location,
+                }));
+            }
+            FrameIterState::Frames(frames) => frames,
+        };
+
+        let loc = frames.next.take();
+        let func = match frames.inlined_functions.next() {
+            Some(func) => func,
+            None => {
+                let frame = Frame {
+                    dw_die_offset: Some(frames.function.dw_die_offset),
+                    function: frames.function.name.clone().map(|name| FunctionName {
+                        name,
+                        language: frames.unit.lang,
+                    }),
+                    location: loc,
+                };
+                self.0 = FrameIterState::Empty;
+                return Ok(Some(frame));
+            }
+        };
+
+        let mut next = Location {
+            file: None,
+            line: if func.call_line != 0 {
+                Some(func.call_line)
+            } else {
+                None
+            },
+            column: if func.call_column != 0 {
+                Some(func.call_column)
+            } else {
+                None
+            },
+        };
+        if let Some(call_file) = func.call_file {
+            if let Some(lines) = frames.unit.parse_lines(frames.sections)? {
+                next.file = lines.files.get(call_file as usize).map(String::as_str);
+            }
+        }
+        frames.next = Some(next);
+
+        Ok(Some(Frame {
+            dw_die_offset: Some(func.dw_die_offset),
+            function: func.name.clone().map(|name| FunctionName {
+                name,
+                language: frames.unit.lang,
+            }),
+            location: loc,
+        }))
+    }
+}
+
+#[cfg(feature = "fallible-iterator")]
+impl<'ctx, R> fallible_iterator::FallibleIterator for FrameIter<'ctx, R>
+where
+    R: gimli::Reader + 'ctx,
+{
+    type Item = Frame<'ctx, R>;
+    type Error = Error;
+
+    #[inline]
+    fn next(&mut self) -> Result<Option<Frame<'ctx, R>>, Error> {
+        self.next()
+    }
+}
+
+/// A function frame.
+pub struct Frame<'ctx, R: gimli::Reader> {
+    /// The DWARF unit offset corresponding to the DIE of the function.
+    pub dw_die_offset: Option<gimli::UnitOffset<R::Offset>>,
+    /// The name of the function.
+    pub function: Option<FunctionName<R>>,
+    /// The source location corresponding to this frame.
+    pub location: Option<Location<'ctx>>,
+}
+
+/// A function name.
+pub struct FunctionName<R: gimli::Reader> {
+    /// The name of the function.
+    pub name: R,
+    /// The language of the compilation unit containing this function.
+    pub language: Option<gimli::DwLang>,
+}
+
+impl<R: gimli::Reader> FunctionName<R> {
+    /// The raw name of this function before demangling.
+    pub fn raw_name(&self) -> Result<Cow<'_, str>, Error> {
+        self.name.to_string_lossy()
+    }
+
+    /// The name of this function after demangling (if applicable).
+    pub fn demangle(&self) -> Result<Cow<'_, str>, Error> {
+        self.raw_name().map(|x| demangle_auto(x, self.language))
+    }
+}
+
+/// Demangle a symbol name using the demangling scheme for the given language.
+///
+/// Returns `None` if demangling failed or is not required.
+#[allow(unused_variables)]
+pub fn demangle(name: &str, language: gimli::DwLang) -> Option<String> {
+    match language {
+        #[cfg(feature = "rustc-demangle")]
+        gimli::DW_LANG_Rust => rustc_demangle::try_demangle(name)
+            .ok()
+            .as_ref()
+            .map(|x| format!("{:#}", x)),
+        #[cfg(feature = "cpp_demangle")]
+        gimli::DW_LANG_C_plus_plus
+        | gimli::DW_LANG_C_plus_plus_03
+        | gimli::DW_LANG_C_plus_plus_11
+        | gimli::DW_LANG_C_plus_plus_14 => cpp_demangle::Symbol::new(name)
+            .ok()
+            .and_then(|x| x.demangle(&Default::default()).ok()),
+        _ => None,
+    }
+}
+
+/// Apply 'best effort' demangling of a symbol name.
+///
+/// If `language` is given, then only the demangling scheme for that language
+/// is used.
+///
+/// If `language` is `None`, then heuristics are used to determine how to
+/// demangle the name. Currently, these heuristics are very basic.
+///
+/// If demangling fails or is not required, then `name` is returned unchanged.
+pub fn demangle_auto(name: Cow<'_, str>, language: Option<gimli::DwLang>) -> Cow<'_, str> {
+    match language {
+        Some(language) => demangle(name.as_ref(), language),
+        None => demangle(name.as_ref(), gimli::DW_LANG_Rust)
+            .or_else(|| demangle(name.as_ref(), gimli::DW_LANG_C_plus_plus)),
+    }
+    .map(Cow::from)
+    .unwrap_or(name)
+}
+
+/// A source location.
+pub struct Location<'a> {
+    /// The file name.
+    pub file: Option<&'a str>,
+    /// The line number.
+    pub line: Option<u32>,
+    /// The column number.
+    pub column: Option<u32>,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn context_is_send() {
+        fn assert_is_send<T: Send>() {}
+        assert_is_send::<crate::Context<gimli::read::EndianSlice<'_, gimli::LittleEndian>>>();
+    }
+}