diff --git a/README.md b/README.md new file mode 100644 index 0000000..33d9a4d --- /dev/null +++ b/README.md @@ -0,0 +1,46 @@ +Unwinding library in Rust and for Rust +====================================== + +This library serves two purposes: +1. Provide a pure Rust alternative to libgcc_eh or libunwind. +2. Provide easier unwinding support for `#![no_std]` targets. + +## Unwinder + +The unwinder can be enabled with `unwinder` feature. Here are the feature gates related to +the unwinder: +| Feature | Default | Description | +|--------------|---------|-| +| unwinder | Yes | The primary feature gate to enable the unwinder | +| fde-phdr | Yes | Use `dl_iterator_phdr` to retrieve frame unwind table. Depends on libc. | +| fde-registry | Yes | Provide `__register__frame` and others for dynamic registration | +| dwarf-expr | Yes | Enable the dwarf expression evaluator. Usually not necessary for Rust | +| hide-trace | Yes | Hide unwinder frames in back trace | + +If you want to use the unwinder for other Rust (C++, or any programs that utilize the unwinder), you can build the [`unwind_dyn`](cdylib) crate provided, and use `LD_PRELOAD` to replace the system unwinder with it. +```sh +cd cdylib +cargo build --release +# Test the unwinder using rustc. Why not :) +LD_PRELOAD=`../target/release/libunwind_dyn.so` rustc +nightly -Ztreat-err-as-bug +``` + +If you want to link to the unwinder in a Rust binary, simply add +```rust +extern crate unwind; +``` + +## Personality and other utilities + +The library also provides Rust personality function. This can be handy if you are working on a `#![no_std]` binary/staticlib/cdylib and you still want unwinding support. + +Here are the feature gates related: +| Feature | Default | Description | +|---------------|---------|-| +| personality | No | Provides `#[lang = eh_personality]` | +| print | No | Provides `(e)?print(ln)?`. This is really only here because panic handler needs to provide things. Depends on libc. | +| panic | No | Provides `begin_panic` and `catch_unwind`. Only stack unwinding functionality is provided and no printing is done, because this feature does not depend on libc. | +| panic-handler | No | Provides `#[panic_handler]`. Provides similar behaviour on panic to std, with `RUST_BACKTRACE` support as well. Stack trace won't have symbols though. Depends on libc. | +| system-alloc | No | Provides a global allocator which calls `malloc` and friends. Provided for convience. | + +If you are writing a `#![no_std]` program, simply enable `personality`, `panic-handler` and `system-alloc` in addition to the defaults, you instantly obtains the ability to do unwinding! An example is given in [`example/`](example).