Auto merge of #11530 - jdm:sigsegv, r=metajack

Obtain backtraces automatically from segfaults

<!-- Please describe your changes on the following line: -->
This enables more meaningful output from observing hard crashes outside of GDB through the judicious use of a SIGSEGV signal handler.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #9371 (github issue number if applicable).
- [X] There are tests for these changes OR

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

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components/servo/Cargo.lock

@@ -3,6 +3,7 @@ name = "servo"
 version = "0.0.1"
 dependencies = [
  "android_glue 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "browserhtml 0.1.7 (git+https://github.com/browserhtml/browserhtml?branch=gh-pages)",
  "canvas 0.0.1",
  "canvas_traits 0.0.1",
@@ -37,6 +38,7 @@ dependencies = [
  "script_layout_interface 0.0.1",
  "script_tests 0.0.1",
  "script_traits 0.0.1",
+ "sig 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "style_tests 0.0.1",
  "url 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2159,6 +2161,11 @@ dependencies = [
  "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "sig"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "simd"
 version = "0.1.0"

components/servo/Cargo.toml

@@ -75,6 +75,10 @@ euclid = "0.6.4"
 libc = "0.2"
 url = "1.0.0"
 
+[target.'cfg(not(target_os = "android"))'.dependencies]
+sig = "0.1"
+backtrace = "0.2"
+
 [target.'cfg(target_os = "android")'.dependencies]
 log = "0.3"
 android_glue = "0.1.3"

components/servo/main.rs

@@ -15,11 +15,13 @@
 //!
 //! [glutin]: https://github.com/tomaka/glutin
 
-#![feature(start)]
+#![feature(start, core_intrinsics)]
 
 #[cfg(target_os = "android")]
 #[macro_use]
 extern crate android_glue;
+#[cfg(not(target_os = "android"))]
+extern crate backtrace;
 extern crate env_logger;
 // The window backed by glutin
 extern crate glutin_app as app;
@@ -30,6 +32,9 @@ extern crate libc;
 extern crate log;
 // The Servo engine
 extern crate servo;
+#[cfg(not(target_os = "android"))]
+#[macro_use]
+extern crate sig;
 
 use servo::Browser;
 use servo::compositing::windowing::WindowEvent;
@@ -48,7 +53,33 @@ pub mod platform {
     pub fn deinit() {}
 }
 
+#[cfg(not(target_os = "android"))]
+fn install_crash_handler() {
+    use backtrace::Backtrace;
+    use sig::ffi::Sig;
+    use std::intrinsics::abort;
+    use std::thread;
+
+    fn handler(_sig: i32) {
+        let name = thread::current().name()
+                                    .map(|n| format!(" for thread \"{}\"", n))
+                                    .unwrap_or("".to_owned());
+        println!("Stack trace{}\n{:?}", name, Backtrace::new());
+        unsafe {
+            abort();
+        }
+    }
+
+    signal!(Sig::SEGV, handler);
+}
+
+#[cfg(target_os = "android")]
+fn install_crash_handler() {
+}
+
 fn main() {
+    install_crash_handler();
+
     // Parse the command line options and store them globally
     let opts_result = opts::from_cmdline_args(&*args());