From 78a49ef9bb58b00aadb67703af33ad41159b0866 Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Tue, 2 Feb 2021 13:32:23 -0800 Subject: [PATCH] Document unwinding limitations Following the discussion in #397 seems like this is a missing section of the documentation! It seems worthwhile to document some pitfalls and mitigations if possible. --- src/lib.rs | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/src/lib.rs b/src/lib.rs index 9d4153bb9..463a5a81b 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -40,6 +40,51 @@ //! } //! # } //! ``` +//! +//! # Backtrace accuracy +//! +//! This crate implements best-effort attempts to get the native backtrace. This +//! is not always guaranteed to work, and some platforms don't return any +//! backtrace at all. If your application requires accurate backtraces then it's +//! recommended to closely evaluate this crate to see whether it's suitable +//! for your use case on your target platforms. +//! +//! Even on supported platforms, there's a number of reasons that backtraces may +//! be less-than-accurate, including but not limited to: +//! +//! * Unwind information may not be available. This crate primarily implements +//! backtraces by unwinding the stack, but not all functions may have +//! unwinding information (e.g. DWARF unwinding information). +//! +//! * Rust code may be compiled without unwinding information for some +//! functions. This can also happen for Rust code compiled with +//! `-Cpanic=abort`. You can remedy this, however, with +//! `-Cforce-unwind-tables` as a compiler option. +//! +//! * Unwind information may be inaccurate or corrupt. In the worst case +//! inaccurate unwind information can lead this library to segfault. In the +//! best case inaccurate information will result in a truncated stack trace. +//! +//! * Backtraces may not report filenames/line numbers correctly due to missing +//! or corrupt debug information. This won't lead to segfaults unlike corrupt +//! unwinding information, but missing or malformed debug information will +//! mean that filenames and line numbers will not be available. This may be +//! because debug information wasn't generated by the compiler, or it's just +//! missing on the filesystem. +//! +//! * Not all platforms are supported. For example there's no way to get a +//! backtrace on WebAssembly at the moment. +//! +//! * Crate features may be disabled. Currently this crate supports using Gimli +//! libbacktrace on non-Windows platforms for reading debuginfo for +//! backtraces. If both crate features are disabled, however, then these +//! platforms will generate a backtrace but be unable to generate symbols for +//! it. +//! +//! In most standard workflows for most standard platforms you generally don't +//! need to worry about these caveats. We'll try to fix ones where we can over +//! time, but otherwise it's important to be aware of the limitations of +//! unwinding-based backtraces! #![doc(html_root_url = "https://docs.rs/backtrace")] #![deny(missing_docs)]