Auto merge of #40684 - alexcrichton:another-bet-anext, r=brson

[beta] std: Back out backtrace pruning logic on beta

It was discovered #40264 that this backtrace pruning logic is a little too
aggressive, so while we figure how out to handle #40264 this commit backs out
the changes on beta to prune frames. Note that other cosmetic changes, such as
better path printing and such remain.

src/ci/docker/emscripten/build-emscripten.sh

@@ -29,7 +29,24 @@ exit 1
 }
 
 curl https://s3.amazonaws.com/mozilla-games/emscripten/releases/emsdk-portable.tar.gz | \
-      tar xzf -
+    tar xzf -
+
+# Some versions of the EMSDK archive have their contents in .emsdk-portable
+# and others in emsdk_portable. Make sure the EMSDK ends up in a fixed path.
+if [ -d emsdk-portable ]; then
+    mv emsdk-portable emsdk_portable
+fi
+
+if [ ! -d emsdk_portable ]; then
+    echo "ERROR: Invalid emsdk archive. Dumping working directory." >&2
+    ls -l
+    exit 1
+fi
+
+# Some versions of the EMSDK set the permissions of the root directory to
+# 0700. Ensure the directory is readable by all users.
+chmod 755 emsdk_portable
+
 source emsdk_portable/emsdk_env.sh
 hide_output emsdk update
 hide_output emsdk install --build=Release sdk-tag-1.37.1-32bit

src/libstd/sys_common/backtrace.rs

@@ -93,87 +93,11 @@ fn _print(w: &mut Write, format: PrintFormat) -> io::Result<()> {
     Ok(())
 }
 
-fn filter_frames(frames: &[Frame],
-                 format: PrintFormat,
-                 context: &BacktraceContext) -> (usize, usize)
+fn filter_frames(_frames: &[Frame],
+                 _format: PrintFormat,
+                 _context: &BacktraceContext) -> (usize, usize)
 {
-    if format == PrintFormat::Full {
-        return (0, 0);
-    }
-
-    // We want to filter out frames with some prefixes
-    // from both top and bottom of the call stack.
-    static BAD_PREFIXES_TOP: &'static [&'static str] = &[
-        "_ZN3std3sys3imp9backtrace",
-        "ZN3std3sys3imp9backtrace",
-        "std::sys::imp::backtrace",
-        "_ZN3std10sys_common9backtrace",
-        "ZN3std10sys_common9backtrace",
-        "std::sys_common::backtrace",
-        "_ZN3std9panicking",
-        "ZN3std9panicking",
-        "std::panicking",
-        "_ZN4core9panicking",
-        "ZN4core9panicking",
-        "core::panicking",
-        "_ZN4core6result13unwrap_failed",
-        "ZN4core6result13unwrap_failed",
-        "core::result::unwrap_failed",
-        "rust_begin_unwind",
-        "_ZN4drop",
-        "mingw_set_invalid_parameter_handler",
-    ];
-    static BAD_PREFIXES_BOTTOM: &'static [&'static str] = &[
-        "_ZN3std9panicking",
-        "ZN3std9panicking",
-        "std::panicking",
-        "_ZN3std5panic",
-        "ZN3std5panic",
-        "std::panic",
-        "_ZN4core9panicking",
-        "ZN4core9panicking",
-        "core::panicking",
-        "_ZN3std2rt10lang_start",
-        "ZN3std2rt10lang_start",
-        "std::rt::lang_start",
-        "panic_unwind::__rust_maybe_catch_panic",
-        "__rust_maybe_catch_panic",
-        "_rust_maybe_catch_panic",
-        "__libc_start_main",
-        "__rust_try",
-        "_start",
-        "main",
-        "BaseThreadInitThunk",
-        "RtlInitializeExceptionChain",
-        "__scrt_common_main_seh",
-        "_ZN4drop",
-        "mingw_set_invalid_parameter_handler",
-    ];
-
-    let is_good_frame = |frame: Frame, bad_prefixes: &[&str]| {
-        resolve_symname(frame, |symname| {
-            if let Some(mangled_symbol_name) = symname {
-                if !bad_prefixes.iter().any(|s| mangled_symbol_name.starts_with(s)) {
-                    return Ok(())
-                }
-            }
-            Err(io::Error::from(io::ErrorKind::Other))
-        }, context).is_ok()
-    };
-
-    let skipped_before = frames.iter().position(|frame| {
-        is_good_frame(*frame, BAD_PREFIXES_TOP)
-    }).unwrap_or(frames.len());
-    let skipped_after = frames[skipped_before..].iter().rev().position(|frame| {
-        is_good_frame(*frame, BAD_PREFIXES_BOTTOM)
-    }).unwrap_or(frames.len() - skipped_before);
-
-    if skipped_before + skipped_after == frames.len() {
-        // Avoid showing completely empty backtraces
-        return (0, 0);
-    }
-
-    (skipped_before, skipped_after)
+    (0, 0)
 }
 
 /// Controls how the backtrace should be formated.