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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---
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components/script/dom/testbinding.rs

@@ -571,6 +571,15 @@ impl TestBindingMethods for TestBinding {
     fn FuncControlledAttributeEnabled(&self) -> bool { false }
     fn FuncControlledMethodDisabled(&self) {}
     fn FuncControlledMethodEnabled(&self) {}
+
+    #[allow(unsafe_code)]
+    fn CrashHard(&self) {
+        static READ_ONLY_VALUE: i32 = 0;
+        unsafe {
+            let p: *mut u32 = &READ_ONLY_VALUE as *const _ as *mut _;
+            ptr::write_volatile(p, 0xbaadc0de);
+        }
+    }
 }
 
 impl TestBinding {

components/script/dom/webidls/TestBinding.webidl

@@ -456,3 +456,8 @@ interface TestBinding {
   [Func="TestBinding::condition_satisfied"]
   const unsigned short funcControlledConstEnabled = 0;
 };
+
+partial interface TestBinding {
+  [Pref="dom.testable_crash.enabled"]
+  void crashHard();
+};

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());
 

ports/cef/Cargo.lock

@@ -1909,6 +1909,7 @@ 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",
@@ -1935,6 +1936,7 @@ dependencies = [
  "script 0.0.1",
  "script_layout_interface 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",
  "url 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
@@ -2044,6 +2046,11 @@ 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"

resources/prefs.json

@@ -4,6 +4,7 @@
   "dom.mouseevent.which.enabled": false,
   "dom.mozbrowser.enabled": false,
   "dom.serviceworker.timeout_seconds": 60,
+  "dom.testable_crash.enabled": false,
   "dom.testbinding.enabled": false,
   "gfx.webrender.enabled": false,
   "js.baseline.enabled": true,

tests/wpt/mozilla/meta/MANIFEST.json

@@ -6952,6 +6952,12 @@
             "url": "/_mozilla/mozilla/service-workers/service-worker-registration.html"
           }
         ],
+        "mozilla/sigsegv.html": [
+          {
+            "path": "mozilla/sigsegv.html",
+            "url": "/_mozilla/mozilla/sigsegv.html"
+          }
+        ],
         "mozilla/storage.html": [
           {
             "path": "mozilla/storage.html",

tests/wpt/mozilla/meta/mozilla/sigsegv.html.ini

@@ -0,0 +1,4 @@
+[sigsegv.html]
+  type: testharness
+  prefs: [dom.testbinding.enabled:true,dom.testable_crash.enabled:true]
+  expected: CRASH

tests/wpt/mozilla/tests/mozilla/sigsegv.html

@@ -0,0 +1,8 @@
+<!doctype html>
+<meta charset="utf-8">
+<title></title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+(new TestBinding()).crashHard();
+</script>