Auto merge of #38165 - Yamakaky:better-backtrace, r=petrochenkov

Improve backtrace formating while panicking.

Fixes #37783.

Done:

- Fix alignment of file paths for better readability
- `RUST_BACKTRACE=full` prints all the informations (current behaviour)
- `RUST_BACKTRACE=(short|yes)` is the default and does:
  - Skip irrelevant frames at the beginning and the end
  - Remove function address
  - Remove the current directory from the absolute paths
  - Remove `::hfabe6541873` at the end of the symbols
- `RUST_BACKTRACE=(0|no)` disables the backtrace.
- `RUST_BACKTRACE=<everything else>` is equivalent to `short` for
  backward compatibility.
- doc
- More uniform printing across platforms.

Removed, TODO in a new PR:

- Remove path prefix for libraries and libstd

Example of short backtrace:
```rust
fn fail() {
    panic!();
}

fn main() {
    let closure = || fail();
    closure();
}
```
Short:
```
thread 'main' panicked at 'explicit panic', t.rs:2
Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: t::fail
            at ./t.rs:2
   1: t::main::{{closure}}
            at ./t.rs:6
   2: t::main
            at ./t.rs:7
```
Full:
```
thread 'main' panicked at 'This function never returns!', t.rs:2
stack backtrace:
   0:     0x558ddf666478 - std::sys::imp::backtrace::tracing::imp::unwind_backtrace::hec84c9dd8389cc5d
                               at /home/yamakaky/dev/rust/rust/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x558ddf65d90e - std::sys_common::backtrace::_print::hfa25f8b31f4b4353
                               at /home/yamakaky/dev/rust/rust/src/libstd/sys_common/backtrace.rs:71
   2:     0x558ddf65cb5e - std::sys_common::backtrace::print::h9b711e11ac3ba805
                               at /home/yamakaky/dev/rust/rust/src/libstd/sys_common/backtrace.rs:60
   3:     0x558ddf66796e - std::panicking::default_hook::{{closure}}::h736d216e74748044
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:355
   4:     0x558ddf66743c - std::panicking::default_hook::h16baff397e46ea10
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:371
   5:     0x558ddf6682bc - std::panicking::rust_panic_with_hook::h6d5a9bb4eca42c80
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:559
   6:     0x558ddf64ea93 - std::panicking::begin_panic::h17dc549df2f10b99
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:521
   7:     0x558ddf64ec42 - t::diverges::he6bc43fc925905f5
                               at /tmp/p/t.rs:2
   8:     0x558ddf64ec5a - t::main::h0ffc20356b8a69c0
                               at /tmp/p/t.rs:6
   9:     0x558ddf6687f5 - core::ops::FnOnce::call_once::hce41f19c0db56f93
  10:     0x558ddf667cde - std::panicking::try::do_call::hd4c8c97efb4291df
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:464
  11:     0x558ddf698d77 - __rust_try
  12:     0x558ddf698c57 - __rust_maybe_catch_panic
                               at /home/yamakaky/dev/rust/rust/src/libpanic_unwind/lib.rs:98
  13:     0x558ddf667adb - std::panicking::try::h2c56ed2a59ec1d12
                               at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:440
  14:     0x558ddf66cc9a - std::panic::catch_unwind::h390834e0251cc9af
                               at /home/yamakaky/dev/rust/rust/src/libstd/panic.rs:361
  15:     0x558ddf6809ee - std::rt::lang_start::hb73087428e233982
                               at /home/yamakaky/dev/rust/rust/src/libstd/rt.rs:57
  16:     0x558ddf64ec92 - main
  17:     0x7fecb869e290 - __libc_start_main
  18:     0x558ddf64e8b9 - _start
  19:                0x0 - <unknown>
```

1 files changed, 156 insertions, 0 deletions

diff --git a/src/libstd/sys/windows/backtrace/mod.rs b/src/libstd/sys/windows/backtrace/mod.rs
new file mode 100644
index 00000000000..3c3fd8d3e4a
--- /dev/null
+++ b/src/libstd/sys/windows/backtrace/mod.rs
@@ -0,0 +1,156 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! As always, windows has something very different than unix, we mainly want
+//! to avoid having to depend too much on libunwind for windows.
+//!
+//! If you google around, you'll find a fair bit of references to built-in
+//! functions to get backtraces on windows. It turns out that most of these are
+//! in an external library called dbghelp. I was unable to find this library
+//! via `-ldbghelp`, but it is apparently normal to do the `dlopen` equivalent
+//! of it.
+//!
+//! You'll also find that there's a function called CaptureStackBackTrace
+//! mentioned frequently (which is also easy to use), but sadly I didn't have a
+//! copy of that function in my mingw install (maybe it was broken?). Instead,
+//! this takes the route of using StackWalk64 in order to walk the stack.
+
+#![allow(deprecated)] // dynamic_lib
+
+use io;
+use libc::c_void;
+use mem;
+use ptr;
+use sys::c;
+use sys::dynamic_lib::DynamicLibrary;
+use sys_common::backtrace::Frame;
+
+macro_rules! sym {
+    ($lib:expr, $e:expr, $t:ident) => (
+        $lib.symbol($e).map(|f| unsafe {
+            $crate::mem::transmute::<usize, $t>(f)
+        })
+    )
+}
+
+mod printing;
+
+#[cfg(target_env = "gnu")]
+#[path = "backtrace_gnu.rs"]
+pub mod gnu;
+
+pub use self::printing::{resolve_symname, foreach_symbol_fileline};
+
+pub fn unwind_backtrace(frames: &mut [Frame])
+    -> io::Result<(usize, BacktraceContext)>
+{
+    let dbghelp = DynamicLibrary::open("dbghelp.dll")?;
+
+    // Fetch the symbols necessary from dbghelp.dll
+    let SymInitialize = sym!(dbghelp, "SymInitialize", SymInitializeFn)?;
+    let SymCleanup = sym!(dbghelp, "SymCleanup", SymCleanupFn)?;
+    let StackWalk64 = sym!(dbghelp, "StackWalk64", StackWalk64Fn)?;
+
+    // Allocate necessary structures for doing the stack walk
+    let process = unsafe { c::GetCurrentProcess() };
+    let thread = unsafe { c::GetCurrentThread() };
+    let mut context: c::CONTEXT = unsafe { mem::zeroed() };
+    unsafe { c::RtlCaptureContext(&mut context) };
+    let mut frame: c::STACKFRAME64 = unsafe { mem::zeroed() };
+    let image = init_frame(&mut frame, &context);
+
+    let backtrace_context = BacktraceContext {
+        handle: process,
+        SymCleanup: SymCleanup,
+        dbghelp: dbghelp,
+    };
+
+    // Initialize this process's symbols
+    let ret = unsafe { SymInitialize(process, ptr::null_mut(), c::TRUE) };
+    if ret != c::TRUE {
+        return Ok((0, backtrace_context))
+    }
+
+    // And now that we're done with all the setup, do the stack walking!
+    // Start from -1 to avoid printing this stack frame, which will
+    // always be exactly the same.
+    let mut i = 0;
+    unsafe {
+        while i < frames.len() &&
+              StackWalk64(image, process, thread, &mut frame, &mut context,
+                          ptr::null_mut(),
+                          ptr::null_mut(),
+                          ptr::null_mut(),
+                          ptr::null_mut()) == c::TRUE
+        {
+            let addr = frame.AddrPC.Offset;
+            if addr == frame.AddrReturn.Offset || addr == 0 ||
+               frame.AddrReturn.Offset == 0 { break }
+
+            frames[i] = Frame {
+                symbol_addr: (addr - 1) as *const c_void,
+                exact_position: (addr - 1) as *const c_void,
+            };
+            i += 1;
+        }
+    }
+
+    Ok((i, backtrace_context))
+}
+
+type SymInitializeFn =
+    unsafe extern "system" fn(c::HANDLE, *mut c_void,
+                              c::BOOL) -> c::BOOL;
+type SymCleanupFn =
+    unsafe extern "system" fn(c::HANDLE) -> c::BOOL;
+
+type StackWalk64Fn =
+    unsafe extern "system" fn(c::DWORD, c::HANDLE, c::HANDLE,
+                              *mut c::STACKFRAME64, *mut c::CONTEXT,
+                              *mut c_void, *mut c_void,
+                              *mut c_void, *mut c_void) -> c::BOOL;
+
+#[cfg(target_arch = "x86")]
+fn init_frame(frame: &mut c::STACKFRAME64,
+              ctx: &c::CONTEXT) -> c::DWORD {
+    frame.AddrPC.Offset = ctx.Eip as u64;
+    frame.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    frame.AddrStack.Offset = ctx.Esp as u64;
+    frame.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    frame.AddrFrame.Offset = ctx.Ebp as u64;
+    frame.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    c::IMAGE_FILE_MACHINE_I386
+}
+
+#[cfg(target_arch = "x86_64")]
+fn init_frame(frame: &mut c::STACKFRAME64,
+              ctx: &c::CONTEXT) -> c::DWORD {
+    frame.AddrPC.Offset = ctx.Rip as u64;
+    frame.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    frame.AddrStack.Offset = ctx.Rsp as u64;
+    frame.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    frame.AddrFrame.Offset = ctx.Rbp as u64;
+    frame.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
+    c::IMAGE_FILE_MACHINE_AMD64
+}
+
+pub struct BacktraceContext {
+    handle: c::HANDLE,
+    SymCleanup: SymCleanupFn,
+    // Only used in printing for msvc and not gnu
+    #[allow(dead_code)]
+    dbghelp: DynamicLibrary,
+}
+
+impl Drop for BacktraceContext {
+    fn drop(&mut self) {
+        unsafe { (self.SymCleanup)(self.handle); }
+    }
+}