Initial vendor packages

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

2 files changed, 801 insertions, 0 deletions

diff --git a/vendor/backtrace-ext/src/lib.rs b/vendor/backtrace-ext/src/lib.rs
new file mode 100644
index 0000000..b04c59d
--- /dev/null
+++ b/vendor/backtrace-ext/src/lib.rs
@@ -0,0 +1,277 @@
+//! Minor conveniences on top of the backtrace crate
+//!
+//! See [`short_frames_strict`][] for details.
+use backtrace::*;
+use std::ops::Range;
+
+#[cfg(test)]
+mod test;
+
+/// Gets an iterator over the frames that are part of Rust's "short backtrace" range.
+/// If no such range is found, the full stack is yielded.
+///
+/// Rust generally tries to include special frames on the stack called `rust_end_short_backtrace`
+/// and `rust_begin_short_backtrace` which delimit the "real" stackframes from "gunk" stackframes
+/// like setting up main and invoking the panic runtime. This yields all the "real" frames between
+/// those two (which theoretically can be nothing with enough optimization, although that's unlikely
+/// for any non-trivial program).
+///
+/// If only one of the special frames is present we will only clamp one side of the stack
+/// (similar to `a..` or `..a`). If the special frames are in the wrong order we will discard
+/// them and produce the full stack. If multiple versions of a special frame are found
+/// (I've seen it in the wild), we will pick the "innermost" ones, producing the smallest
+/// possible backtrace (and excluding all special frames from the output).
+///
+/// Each element of the iterator includes a Range which you should use to slice
+/// the frame's `symbols()` array. This handles the theoretical situation where "real" frames
+/// got inlined together with the special marker frames. I want to believe this can't happen
+/// but you can never trust backtraces to be reasonable! We will never yield a Frame to you
+/// with an empty Range.
+///
+/// Note that some "gunk" frames may still be found within the short backtrace, as there is still some
+/// platform-specific and optimization-specific glue around the edges because compilers are
+/// complicated and nothing's perfect. This can include:
+///
+/// * `core::ops::function::FnOnce::call_once`
+/// * `std::panicking::begin_panic_handler`
+/// * `core::panicking::panic_fmt`
+/// * `rust_begin_unwind`
+///
+/// In the future we may introduce a non-strict short_frames which heuristically filters
+/// those frames out too. Until then, the strict approach is safe.
+///
+/// # Example
+///
+/// Here's an example simple "short backtrace" implementation.
+/// Note the use of `sub_frames` for the inner loop to restrict `symbols`!
+///
+/// This example is based off of code found in `miette` (Apache-2.0), which itself
+/// copied the logic from `human-panic` (MIT/Apache-2.0).
+///
+/// FIXME: it would be nice if this example consulted `RUST_BACKTRACE=full`,
+/// and maybe other vars used by rust's builtin panic handler..?
+///
+/// ```
+/// fn backtrace() -> String {
+///     use std::fmt::Write;
+///     if let Ok(var) = std::env::var("RUST_BACKTRACE") {
+///         if !var.is_empty() && var != "0" {
+///             const HEX_WIDTH: usize = std::mem::size_of::<usize>() + 2;
+///             // Padding for next lines after frame's address
+///             const NEXT_SYMBOL_PADDING: usize = HEX_WIDTH + 6;
+///             let mut backtrace = String::new();
+///             let trace = backtrace::Backtrace::new();
+///             let frames = backtrace_ext::short_frames_strict(&trace).enumerate();
+///             for (idx, (frame, subframes)) in frames {
+///                 let ip = frame.ip();
+///                 let _ = write!(backtrace, "\n{:4}: {:2$?}", idx, ip, HEX_WIDTH);
+///     
+///                 let symbols = frame.symbols();
+///                 if symbols.is_empty() {
+///                     let _ = write!(backtrace, " - <unresolved>");
+///                     continue;
+///                 }
+///     
+///                 for (idx, symbol) in symbols[subframes].iter().enumerate() {
+///                     // Print symbols from this address,
+///                     // if there are several addresses
+///                     // we need to put it on next line
+///                     if idx != 0 {
+///                         let _ = write!(backtrace, "\n{:1$}", "", NEXT_SYMBOL_PADDING);
+///                     }
+///     
+///                     if let Some(name) = symbol.name() {
+///                         let _ = write!(backtrace, " - {}", name);
+///                     } else {
+///                         let _ = write!(backtrace, " - <unknown>");
+///                     }
+///     
+///                     // See if there is debug information with file name and line
+///                     if let (Some(file), Some(line)) = (symbol.filename(), symbol.lineno()) {
+///                         let _ = write!(
+///                             backtrace,
+///                             "\n{:3$}at {}:{}",
+///                             "",
+///                             file.display(),
+///                             line,
+///                             NEXT_SYMBOL_PADDING
+///                         );
+///                     }
+///                 }
+///             }
+///             return backtrace;
+///         }
+///     }
+///     "".into()
+/// }
+/// ```
+pub fn short_frames_strict(
+    backtrace: &Backtrace,
+) -> impl Iterator<Item = (&BacktraceFrame, Range<usize>)> {
+    short_frames_strict_impl(backtrace)
+}
+
+pub(crate) fn short_frames_strict_impl<B: Backtraceish>(
+    backtrace: &B,
+) -> impl Iterator<Item = (&B::Frame, Range<usize>)> {
+    // Search for the special frames
+    let mut short_start = None;
+    let mut short_end = None;
+    let frames = backtrace.frames();
+    for (frame_idx, frame) in frames.iter().enumerate() {
+        let symbols = frame.symbols();
+        for (subframe_idx, frame) in symbols.iter().enumerate() {
+            if let Some(name) = frame.name_str() {
+                // Yes these ARE backwards, and that's intentional! We want to print the frames from
+                // "newest to oldest" (show what panicked first), and that's the order that Backtrace
+                // gives us, but these magic labels view the stack in the opposite order. So we just
+                // swap it once here and forget about that weirdness.
+                //
+                // Note that due to platform/optimization wobblyness you can end up with multiple frames
+                // that contain these names in sequence. If that happens we just want to pick the two
+                // that are closest together. For the start that means just using the last one we found,
+                // and for the end that means taking the first one we find.
+                if name.contains("rust_end_short_backtrace") {
+                    short_start = Some((frame_idx, subframe_idx));
+                }
+                if name.contains("rust_begin_short_backtrace") && short_end.is_none() {
+                    short_end = Some((frame_idx, subframe_idx));
+                }
+            }
+        }
+    }
+
+    // Check if these are in the right order, if they aren't, discard them
+    // This also handles the mega-cursed case of "someone made a symbol with both names
+    // so actually they're the exact same subframe".
+    if let (Some(start), Some(end)) = (short_start, short_end) {
+        if start >= end {
+            short_start = None;
+            short_end = None;
+        }
+    }
+
+    // By default we want to produce a full stack trace and now we'll try to clamp it.
+    let mut first_frame = 0usize;
+    let mut first_subframe = 0usize;
+    // NOTE: this is INCLUSIVE
+    let mut last_frame = frames.len().saturating_sub(1);
+    // NOTE: this is EXCLUSIVE
+    let mut last_subframe_excl = backtrace
+        .frames()
+        .last()
+        .map(|frame| frame.symbols().len())
+        .unwrap_or(0);
+
+    // This code tries to be really paranoid about boundary conditions although in practice
+    // most of them are impossible because there's always going to be gunk on either side
+    // of the short backtrace to smooth out the boundaries, and panic_fmt is basically
+    // impossible to optimize out. Still, don't trust backtracers!!!
+    //
+    // This library has a fuckton of tests to try to catch all the little corner cases here.
+
+    // If we found the start bound...
+    if let Some((idx, sub_idx)) = short_start {
+        if frames[idx].symbols().len() == sub_idx + 1 {
+            // If it was the last subframe of this frame, we want to just
+            // use the whole next frame! It's ok if this takes us to `first_frame = len`,
+            // that will be properly handled as an empty output
+            first_frame = idx + 1;
+            first_subframe = 0;
+        } else {
+            // Otherwise use this frame, and all the subframes after it
+            first_frame = idx;
+            first_subframe = sub_idx + 1;
+        }
+    }
+
+    // If we found the end bound...
+    if let Some((idx, sub_idx)) = short_end {
+        if sub_idx == 0 {
+            // If it was the first subframe of this frame, we want to just
+            // use the whole previous frame!
+            if idx == 0 {
+                // If we were *also* on the first frame, set subframe_excl
+                // to 0, indicating an empty output
+                last_frame = 0;
+                last_subframe_excl = 0;
+            } else {
+                last_frame = idx - 1;
+                last_subframe_excl = frames[last_frame].symbols().len();
+            }
+        } else {
+            // Otherwise use this frame (no need subframe math, exclusive bound!)
+            last_frame = idx;
+            last_subframe_excl = sub_idx;
+        }
+    }
+
+    // If the two subframes managed to perfectly line up with eachother, just
+    // throw everything out and yield an empty range. We don't need to fix any
+    // other values at this point as they won't be used for anything with an
+    // empty iterator
+    let final_frames = {
+        let start = (first_frame, first_subframe);
+        let end = (last_frame, last_subframe_excl);
+        if start == end {
+            &frames[0..0]
+        } else {
+            &frames[first_frame..=last_frame]
+        }
+    };
+
+    // Get the index of the last frame when starting from the first frame
+    let adjusted_last_frame = last_frame.saturating_sub(first_frame);
+
+    // finally do the iteration
+    final_frames.iter().enumerate().map(move |(idx, frame)| {
+        // Default to all subframes being yielded
+        let mut sub_start = 0;
+        let mut sub_end_excl = frame.symbols().len();
+        // If we're on first frame, apply its subframe clamp
+        if idx == 0 {
+            sub_start = first_subframe;
+        }
+        // If we're on the last frame, apply its subframe clamp
+        if idx == adjusted_last_frame {
+            sub_end_excl = last_subframe_excl;
+        }
+        (frame, sub_start..sub_end_excl)
+    })
+}
+
+pub(crate) trait Backtraceish {
+    type Frame: Frameish;
+    fn frames(&self) -> &[Self::Frame];
+}
+
+pub(crate) trait Frameish {
+    type Symbol: Symbolish;
+    fn symbols(&self) -> &[Self::Symbol];
+}
+
+pub(crate) trait Symbolish {
+    fn name_str(&self) -> Option<&str>;
+}
+
+impl Backtraceish for Backtrace {
+    type Frame = BacktraceFrame;
+    fn frames(&self) -> &[Self::Frame] {
+        self.frames()
+    }
+}
+
+impl Frameish for BacktraceFrame {
+    type Symbol = BacktraceSymbol;
+    fn symbols(&self) -> &[Self::Symbol] {
+        self.symbols()
+    }
+}
+
+impl Symbolish for BacktraceSymbol {
+    // We need to shortcut SymbolName here because
+    // HRTB isn't in our msrv
+    fn name_str(&self) -> Option<&str> {
+        self.name().and_then(|n| n.as_str())
+    }
+}
diff --git a/vendor/backtrace-ext/src/test.rs b/vendor/backtrace-ext/src/test.rs
new file mode 100644
index 0000000..d4d4112
--- /dev/null
+++ b/vendor/backtrace-ext/src/test.rs
@@ -0,0 +1,524 @@
+use super::*;
+
+type BT = &'static [&'static [&'static str]];
+
+impl Backtraceish for BT {
+    type Frame = &'static [&'static str];
+    fn frames(&self) -> &[Self::Frame] {
+        self
+    }
+}
+
+impl Frameish for &'static [&'static str] {
+    type Symbol = &'static str;
+    fn symbols(&self) -> &[Self::Symbol] {
+        self
+    }
+}
+
+impl Symbolish for &'static str {
+    fn name_str(&self) -> Option<&str> {
+        Some(self)
+    }
+}
+
+fn process(bt: BT) -> Vec<&'static str> {
+    let mut result = vec![];
+    for (frame, subframes) in short_frames_strict_impl(&bt) {
+        let symbols = &frame.symbols()[subframes];
+        assert!(!symbols.is_empty());
+        for symbol in symbols {
+            result.push(*symbol);
+        }
+    }
+    result
+}
+
+#[test]
+fn test_full() {
+    let bt: BT = &[&["hello"], &["there", "simple"], &["case"]];
+    let expected = vec!["hello", "there", "simple", "case"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_empty() {
+    let bt: BT = &[];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_cursed_one_true_symbol1() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_end_short_backtrace_rust_begin_short_backtrace"],
+        &["there"],
+    ];
+    let expected = vec![
+        "hello",
+        "__rust_end_short_backtrace_rust_begin_short_backtrace",
+        "there",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_cursed_one_true_symbol2() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_begin_short_backtrace_rust_end_short_backtrace"],
+        &["there"],
+    ];
+    let expected: Vec<&str> = vec![
+        "hello",
+        "__rust_begin_short_backtrace_rust_end_short_backtrace",
+        "there",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_backwards1() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_begin_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_end_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "__rust_begin_short_backtrace",
+        "real",
+        "frames",
+        "rust_end_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_backwards2() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_begin_short_backtrace", "real", "frames"],
+        &["rust_end_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "__rust_begin_short_backtrace",
+        "real",
+        "frames",
+        "rust_end_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_backwards3() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_begin_short_backtrace"],
+        &["real", "frames", "rust_end_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "__rust_begin_short_backtrace",
+        "real",
+        "frames",
+        "rust_end_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_backwards4() {
+    let bt: BT = &[
+        &["hello"],
+        &[
+            "__rust_begin_short_backtrace",
+            "real",
+            "frames",
+            "rust_end_short_backtrace",
+        ],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "__rust_begin_short_backtrace",
+        "real",
+        "frames",
+        "rust_end_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_begin_clamp_simple() {
+    let bt: BT = &[&["hello"], &["__rust_begin_short_backtrace"], &["case"]];
+    let expected = vec!["hello"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_begin_clamp_left_edge() {
+    let bt: BT = &[&["__rust_begin_short_backtrace"], &["case"]];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_begin_clamp_right_edge() {
+    let bt: BT = &[&["hello"], &["__rust_begin_short_backtrace"]];
+    let expected = vec!["hello"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_begin_clamp_empty() {
+    let bt: BT = &[&["__rust_begin_short_backtrace"]];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_begin_clamp_sub() {
+    let bt: BT = &[
+        &["real"],
+        &["frames", "core::rust_begin_short_backtrace", "junk"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_end_clamp_simple() {
+    let bt: BT = &[&["hello"], &["__rust_end_short_backtrace"], &["case"]];
+    let expected = vec!["case"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_end_clamp_left_edge() {
+    let bt: BT = &[&["_rust_end_short_backtrace"], &["case"]];
+    let expected = vec!["case"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_end_clamp_right_edge() {
+    let bt: BT = &[&["hello"], &["__rust_end_short_backtrace"]];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_end_clamp_empty() {
+    let bt: BT = &[&["__rust_end_short_backtrace"]];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_end_clamp_sub() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace", "real"],
+        &["frames"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_simple() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_multiball_various() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_end_short_backtrace"],
+        &["core::rust_end_short_backtrace"],
+        &["junk"],
+        &["rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["_rust_begin_short_backtrace"],
+        &["junk"],
+        &["core::rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_multiball_identical() {
+    let bt: BT = &[
+        &["hello"],
+        &["rust_end_short_backtrace"],
+        &["rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_multiball_invert1() {
+    let bt: BT = &[
+        &["hello"],
+        &["rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["junk"],
+        &["rust_end_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "rust_end_short_backtrace",
+        "real",
+        "frames",
+        "rust_begin_short_backtrace",
+        "junk",
+        "rust_end_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_multiball_invert2() {
+    let bt: BT = &[
+        &["hello"],
+        &["rust_begin_short_backtrace"],
+        &["junk"],
+        &["rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec![
+        "hello",
+        "rust_begin_short_backtrace",
+        "junk",
+        "rust_end_short_backtrace",
+        "real",
+        "frames",
+        "rust_begin_short_backtrace",
+        "case",
+    ];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_adjacent() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_end_short_backtrace"],
+        &["rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_left_edge() {
+    let bt: BT = &[
+        &["__rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+        &["case"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_right_edge() {
+    let bt: BT = &[
+        &["hello"],
+        &["__rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["rust_begin_short_backtrace"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_spanned() {
+    let bt: BT = &[
+        &["__rust_end_short_backtrace"],
+        &["real"],
+        &["frames"],
+        &["__rust_begin_short_backtrace"],
+    ];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_both_spanned_empty() {
+    let bt: BT = &[
+        &["rust_end_short_backtrace"],
+        &["rust_begin_short_backtrace"],
+    ];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_one_super_frame_2() {
+    let bt: BT = &[&[
+        "rust_end_short_backtrace",
+        "real",
+        "frames",
+        "rust_begin_short_backtrace",
+    ]];
+    let expected = vec!["real", "frames"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_one_super_frame_1() {
+    let bt: BT = &[&[
+        "rust_end_short_backtrace",
+        "real",
+        "rust_begin_short_backtrace",
+    ]];
+    let expected = vec!["real"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_one_super_frame_0() {
+    let bt: BT = &[&["rust_end_short_backtrace", "rust_begin_short_backtrace"]];
+    let expected: Vec<&str> = vec![];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex1() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace", "real"],
+        &["frames"],
+        &["here", "__rust_begin_short_backtrace", "junk"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex2() {
+    let bt: BT = &[
+        &["junk"],
+        &["__rust_end_short_backtrace", "real"],
+        &["frames"],
+        &["here", "__rust_begin_short_backtrace", "junk"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex3() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace", "real"],
+        &["frames"],
+        &["here", "__rust_begin_short_backtrace"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex4() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace"],
+        &["real", "frames"],
+        &["here", "__rust_begin_short_backtrace"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex5() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace", "real"],
+        &["frames", "here"],
+        &["__rust_begin_short_backtrace"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex6() {
+    let bt: BT = &[
+        &["junk"],
+        &[
+            "junk",
+            "__rust_end_short_backtrace",
+            "real",
+            "frames",
+            "here",
+        ],
+        &["__rust_begin_short_backtrace"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}
+
+#[test]
+fn test_complex7() {
+    let bt: BT = &[
+        &["junk"],
+        &["junk", "__rust_end_short_backtrace"],
+        &["real", "frames", "here", "__rust_begin_short_backtrace"],
+        &["junk"],
+    ];
+    let expected = vec!["real", "frames", "here"];
+    assert_eq!(process(bt), expected);
+}