Dart VM crash (Access Violation) on Windows (1.12.1)

[DanTup]

While working on some code today using built_value I managed to get the Dart VM to crash (that is, Windows said dart.exe has encountered a problem and had to close rather than the normal exception spat to screen).

I was able to reduce the code to this very small sample:

import 'dart:async';

Future main() async {
  await doThing("test");
}

doThing<T>(String request) async {
  var a = new FullType(T);
}

class FullType {
  FullType(a);
}

When I run this, the VM crashes. I don't think this code logically makes much sense (I don't even know if Generics are supposed to work yet, and there's a mismatch of awaits and non-async code) but it doesn't seem like the VM should crash.

Most tweaks I try to simplify/correct the code stop the crash from occurring.

If I hit Debug in the Windows dialog I get the following information:

Unhandled exception at 0x00007FF60461094A in dart.exe: 0xC0000005:
Access violation reading location 0x0000000000000010.

I'm on Windows 10 Pro x64 running v1.21.1 of the SDK. I have the above code in a .dart file and I'm just running it with dart myfile.dart.

[lrhn]

tl;dr: Shorter reproduction: main<T>() async { T; }. It's the T as an expression in an async function that crashes in the parser.

Running the original example with a debug-X64 build, I get:

../../runtime/vm/parser.cc: 7622: error: expected: FunctionLevel() > 0
Dumping native stack trace for thread 4ce3
  [0x000000000099c503] dart::Profiler::DumpStackTrace()
  [0x000000000099c503] dart::Profiler::DumpStackTrace()
  [0x000000000068d0b1] dart::DynamicAssertionHelper::Fail(char const*, ...)
  [0x00000000009256c0] dart::Parser::ParsePrimary()
  [0x000000000095933c] dart::Parser::ParsePostfixExpr()
  [0x0000000000956b62] dart::Parser::ParseUnaryExpr()
  [0x000000000092ea3d] dart::Parser::ParseBinaryExpr(int)
  [0x0000000000930a16] dart::Parser::ParseConditionalExpr()
  [0x0000000000926598] dart::Parser::ParseExpr(bool, bool)
  [0x000000000092e021] dart::Parser::ParseActualParameters(dart::ArgumentListNode*, bool)
  [0x00000000009235e7] dart::Parser::ParseNewOperator(dart::Token::Kind)
  [0x00000000009251fb] dart::Parser::ParsePrimary()
  [0x000000000095933c] dart::Parser::ParsePostfixExpr()
  [0x0000000000956b62] dart::Parser::ParseUnaryExpr()
  [0x000000000092ea3d] dart::Parser::ParseBinaryExpr(int)
  [0x0000000000930a16] dart::Parser::ParseConditionalExpr()
  [0x0000000000926598] dart::Parser::ParseExpr(bool, bool)
  [0x0000000000936439] dart::Parser::ParseAwaitableExpr(bool, bool, dart::SequenceNode**)
  [0x0000000000949e92] dart::Parser::ParseVariableDeclaration(dart::AbstractType const&, bool, bool, dart::SequenceNode**)
  [0x000000000094a3af] dart::Parser::ParseVariableDeclarationList()
  [0x000000000094c170] dart::Parser::ParseStatement()
  [0x00000000009349da] dart::Parser::ParseStatementSequence()
  [0x000000000091f229] dart::Parser::ParseFunc(dart::Function const&, bool)
  [0x000000000091cf49] dart::Parser::ParseFunction(dart::ParsedFunction*)
  [0x00000000006e9b00] dart::DartCompilationPipeline::ParseFunction(dart::ParsedFunction*)
  [0x00000000006ef3b0] Unknown symbol
  [0x00000000006eee4e] dart::Compiler::CompileFunction(dart::Thread*, dart::Function const&)
  [0x00000000006e9f5b] dart::DRT_CompileFunction(dart::NativeArguments)
  [0x00007f100fd09630] [Stub] CallToRuntime
  [0x00007f100fd096b0] [Stub] LazyCompile
  [0x00007f100e08201d] _Closure.call
  [0x00007f100e08c1d0] Future.Future.microtask.<anonymous closure>
  [0x00007f100e08201d] _Closure.call
  [0x00007f100e08becf] _microtaskLoop
  [0x00007f100e08b9d9] _startMicrotaskLoop
  [0x00007f100e08b887] _startMicrotaskLoop
  [0x00007f100e08201d] _Closure.call
  [0x00007f100e08b731] _runPendingImmediateCallback
  [0x00007f100e0879bf] _RawReceivePortImpl._handleMessage
  [0x00007f100fd09a4b] [Stub] InvokeDartCode
  [0x0000000000707b28] dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&, dart::Array const&, unsigned long)
  [0x00000000007078c4] dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&)
  [0x000000000070ac94] dart::DartLibraryCalls::HandleMessage(dart::Object const&, dart::Instance const&)
  [0x0000000000815fdd] dart::IsolateMessageHandler::HandleMessage(dart::Message*)
  [0x000000000084b049] dart::MessageHandler::HandleMessages(dart::MonitorLocker*, bool, bool)
  [0x000000000084b702] dart::MessageHandler::TaskCallback()
  [0x000000000084c173] Unknown symbol
-- End of DumpStackTrace

That suggests that the crash is in the parser, where the T in doThing is used as an expression in the argument list.

It is supposed to be a compile-time error - using a generic function type parameter as an expression - but not like this :)

[fsc8000]

@crelier

[crelier]

Thanks for the report. The VM should not crash indeed.