Gather demangled stack traces and report the same to console on crashes. by chinmaygarde · Pull Request #11431 · flutter/engine

chinmaygarde · 2019-08-25T00:09:40Z

These should only be used on host binaries for more detailed crash reports. Installing the handler on targets (iOS/Android) may cause use to break existing crash reporting mechanisms users may have installed themselves in the process.

chinmaygarde · 2019-08-25T00:11:25Z

This should work on Darwin & Linux. I'll work on Windows next.

Doing something like int* a = nullptr; *a = 12; or abort or tripping an assertion should print something the following before program termination. We can tweak the report further if necessary.

[ERROR:flutter/fml/backtrace.cc(110)] Caught signal SIGSEGV during program execution.
Frame 0: 0x10658342c void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)
Frame 1: 0x106555070 void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)
Frame 2: 0x106554f81 testing::Test::Run()
Frame 3: 0x106555dc3 testing::TestInfo::Run()
Frame 4: 0x1065570a1 testing::TestSuite::Run()
Frame 5: 0x106562a55 testing::internal::UnitTestImpl::RunAllTests()
Frame 6: 0x10658c22c bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)
Frame 7: 0x1065625c3 bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)
Frame 8: 0x106562445 testing::UnitTest::Run()
Frame 9: 0x105c8dc33 RUN_ALL_TESTS()
Frame 10: 0x105c8dbe6 main
Frame 11: 0x7fff7c2dc3d5 start

dnfield

LGTM!

dnfield · 2019-08-25T04:10:04Z

Looks like you need to add the new files to the license golden file.

dnfield · 2019-08-25T04:10:40Z

/cc @jonahwilliams @zanderso this may be interesting for the tool to capture or treat specially - this will be super helpful if we see crashes in flutter_tester due to e.g. a segfault. /cc also @GaryQian

zanderso · 2019-08-25T04:35:43Z

fml/backtrace.cc

@@ -0,0 +1,132 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.


We use 2013 for all source files in the engine - keeps the license file in better shape.

zanderso · 2019-08-25T04:56:28Z

fml/backtrace.cc

+
+  int status = 0;
+  size_t length = 0;
+  char* demangled = __cxxabiv1::__cxa_demangle(


The Dart VM does an MSAN_UNPOISON() on the result of a similar function. See: https://github.com/dart-lang/sdk/blob/master/runtime/vm/native_symbol_linux.cc#L36.

This comment made me realize that backtrace printing stuff is not signal safe at all. I am closing this and reworking this to only use signal safe routines.

zanderso · 2019-08-25T04:57:17Z

fml/backtrace.cc

+static void ToggleSignalHandlers(bool set);
+
+static void SignalHandler(int signal) {
+  // We are a crash signal handler. This can only happen once. Since we don't


Things to think about, but which don't necessarily need to be solved in this PR:

What (should) happen(s) here when a SIGSEGV was caused by a stack overflow?

What (should) happen(s) here when a SIGABRT was caused by malloc heap corruption?

zanderso · 2019-08-25T05:00:04Z

fml/backtrace.cc

+  // want to catch crashes while we are generating the crash reports, disable
+  // all set signal handlers to their default values before reporting the crash
+  // and re-raising the signal.
+  ToggleSignalHandlers(false);


Will this disable backtrace printing for all threads or only the calling thread?

Printing a backtrace and the signal handling are orthogonal. We will print the backtrace that caused this specific signal and re-raise it. Presumably, this will cause process termination. So there is nothing else to do on other threads.

If ToggleSignalHandlers() only affects the calling thread, and two threads crash at the same time, then the backtrace output could be interleaved.

zanderso · 2019-08-25T05:04:19Z

fml/backtrace.h

@@ -0,0 +1,20 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.


zanderso · 2019-08-25T05:04:28Z

fml/backtrace_unittests.cc

@@ -0,0 +1,33 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.


chinmaygarde · 2019-08-26T01:06:52Z

Closing because of signal unsafe-ness of the backtrace printing. Will rework it to be safe.

googlebot added the cla: yes label Aug 25, 2019

chinmaygarde requested review from cbracken, dnfield and jason-simmons August 25, 2019 00:13

dnfield approved these changes Aug 25, 2019

View reviewed changes

zanderso reviewed Aug 25, 2019

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chinmaygarde closed this Aug 26, 2019

chinmaygarde deleted the crasher branch October 21, 2019 19:41

chinmaygarde mentioned this pull request Feb 6, 2020

Print the backtrace explicitly when assertions are tripped in all unit-test harnesses. flutter/flutter#50244

Closed

		@@ -0,0 +1,132 @@
		// Copyright 2013 The Flutter Authors. All rights reserved.

		@@ -0,0 +1,20 @@
		// Copyright 2013 The Flutter Authors. All rights reserved.

		@@ -0,0 +1,33 @@
		// Copyright 2013 The Flutter Authors. All rights reserved.

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chinmaygarde commented Aug 25, 2019 •

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chinmaygarde commented Aug 26, 2019 •

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