EchoServer tests occasionally crash on Windows #2
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A high priority bug; for example, a single project is unusable or has many test failures
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This was referenced Jun 3, 2015
This was referenced Jun 3, 2015
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Change-Id: Icabef092ce55f981bc6a21819e3733340f037155 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/354043 Commit-Queue: Konstantin Shcheglov <[email protected]> Reviewed-by: Brian Wilkerson <[email protected]>
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During my work on dart-lang/language#3648, I ran into some trybot failures with an exception that looked like this: RangeError (index): Invalid value: Valid value range is empty: -1 #0 List.[] (dart:core-patch/growable_array.dart:264:36) #1 List.removeLast (dart:core-patch/growable_array.dart:336:20) #2 InferenceContext.popFunctionBodyContext (package:analyzer/src/generated/resolver.dart:124:33) #3 ResolverVisitor.visitBlockFunctionBody (package:analyzer/src/generated/resolver.dart:1890:38) Some quick reading of the code revealed that `popFunctionBodyContext` always removed a single entry from a list, and `pushFunctionBodyContext` always added a single entry to it. The two calls were always paired up using a straightforward try/finally pattern that seemed like it should guarantee proper nesting, making this exception impossible: try { inferenceContext.pushFunctionBodyContext(...); ... } finally { ... inferenceContext.popFunctionBodyContext(node); } After a lot of headscratching and experimenting, I eventually figured out what was happening: an exception was being thrown during `pushFunctionBodyContext`, _before_ it had a chance to add an entry to the list. But since the exception happened inside the `try` block, the call to `popFunctionBodyContext` would happen anyway. As a result, the pop would fail, causing its own exception, and the exception that was the original source of the problem would be lost. This seemed like a code smell to me: where possible, the clean-up logic in `finally` clauses should be simple enough that it can always succeed, without causing an exception, even if a previous exception has put data structures in an unexpected state. And I had gained enough familiarity with the code over the course of my debugging to see that what we were doing in those `finally` clauses was more complex than necessary: - In the ResolverVisitor, we were pushing and popping a stack of `BodyInferenceContext` objects using the try/finally pattern described above. But we were only ever accessing the top entry on the stack, which meant that the same state could be maintained with a single BodyInferenceContext pointer, and some logic that can't possibly lead to an exception in the `finally` clause: var oldBodyContext = _bodyContext; try { _bodyContext = ...; ... } finally { _bodyContext = oldBodyContext; } - In the ResolverVisitor and the ErrorVerifier, we were also pushing and popping a stack of booleans tracking whether the currently enclosing function (or initializer) has access to `this`. In the ResolverVisitor, this information wasn't being used at all, so it could be safely removed. In the ErrorVerifier, it was being used, but it was possible to simplify it in a similar way, so that it was tracked with a single boolean (`_hasAccessToThis`), rather than a stack. Simplifying this logic brings several advantages: - As noted above, since it's now impossible for an exception to occur in the `finally` clause, exceptions occurring in the `try` clause won't get lost, making debugging easier. - The code should be more performant, since it no longer requires auxiliary heap-allocated stacks. - The code is (IMHO) easier to understand, since the try/catch pattern for maintaining the new `_bodyContext` and `_hasAccessToThis` fields just involves saving a field in a local variable (and restoring it later), rather than calling out to separate classes. Change-Id: I61ae80fb28a69760ea0b2856a6954b4a68cfcbe1 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/358200 Reviewed-by: Konstantin Shcheglov <[email protected]> Reviewed-by: Brian Wilkerson <[email protected]> Commit-Queue: Paul Berry <[email protected]>
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…ecks The (utf8) scanner currently has this thing where you give it a 0-terminated byte-array (i.e. you read the file, then allocate something that's 1 bigger, copy the data, then give it to the scanner) to 'avoid bounds checks'. Dart still has bounds checks though - they're just implicit. As for the string scanner ut gets a string, then creates a new string like `string + '\x00'` - so basically the same thing. This CL uses the 'vm:unsafe:no-bounds-checks' pragma, removing the implicit bounds checks, adding explicit bounds checks, saving ~73.6 mio instructions when compiling the CFE in the process: ``` Comparing snapshot #1 with snapshot #2 cycles:u: -0.9983% +/- 0.6563% (-174026333.30 +/- 114410028.98) instructions:u: -0.3416% +/- 0.0005% (-73659267.00 +/- 108567.20) branch-misses:u: -4.8952% +/- 2.2612% (-3172939.50 +/- 1465641.18) ``` With the scanner-benchmark with `--bytes` I get this: ``` msec task-clock:u: -1.2251% +/- 0.6355% (-50.64 +/- 26.27) cycles:u: -1.2376% +/- 0.6385% (-223642830.80 +/- 115393789.68) instructions:u: -2.8155% +/- 0.0000% (-1153243856.00 +/- 428.11) seconds time elapsed: -1.2165% +/- 0.6408% (-0.05 +/- 0.03) seconds user: -1.1539% +/- 0.6495% (-0.05 +/- 0.03) ``` With the scanner-benchmark with `--string` I get this: ``` msec task-clock:u: -7.6439% +/- 0.6628% (-366.08 +/- 31.74) page-faults:u: -95.0034% +/- 0.0014% (-228023.50 +/- 3.41) instructions:u: 2.1041% +/- 0.0000% (897941907.60 +/- 2082.79) branch-misses:u: 3.2994% +/- 1.4675% (3239735.30 +/- 1440940.88) seconds time elapsed: -7.6595% +/- 0.6610% (-0.37 +/- 0.03) seconds user: -0.8801% +/- 0.7676% (-0.04 +/- 0.03) seconds sys: -92.0140% +/- 2.8075% (-0.33 +/- 0.01) MarkSweep( old space) goes from 6 to 0 Notice combined GC time goes from 112 ms to 41 ms (notice only 1 run each). ``` Where I'll note that the 'vm:unsafe:no-bounds-checks' pragma doesn't (yet?) work for `String.codeUnitAt`. See https://dart-review.googlesource.com/c/sdk/+/384540 (and https://dart-review.googlesource.com/c/sdk/+/385201) for details. I assume the relatively big change here is caused by not allocating a new string with a 0-byte in the end each time. Note that the read-allocate-copy dance is still performed for the utf8 scanner in this CL as it requires changing all call-sites instead. It will be done in a follow-up CL where the "end-of-file" int will likely also be changed to `-1` to (I assume) allow for having the 0-byte in the middle of a file (see also the 10+ year old bug at #18090) Note: The pragma (currently?) only has effect in AOT and this change will (for the utf8 scanner) make the JIT version slower (probably by the same ~73.6 mio instructions as - at least in AOT - the implicit check is 6 instructions and the explicit one is 3 instructions). As the pragma doesn't work in the StringScanner anyway I expect the change to be somewhat equivalent there. Once the read-allocate-copy dance is also removed from the utf8 scanner I expect the combined result to be positive all around. Update: With https://dart-review.googlesource.com/c/sdk/+/385201 landed I get these changes: Compiling the CFE: ``` instructions:u: -0.4520% +/- 0.0002% (-98470955.29 +/- 42253.40) ``` Scanner benchmark with `--bytes`: ``` msec task-clock:u: -2.1758% +/- 0.2316% (-92.07 +/- 9.80) cycles:u: -2.1941% +/- 0.2283% (-405224983.11 +/- 42160655.88) instructions:u: -3.1049% +/- 0.0000% (-1272360052.95 +/- 706.54) branch-misses:u: 2.4718% +/- 0.5142% (2371345.23 +/- 493257.76) seconds time elapsed: -2.1761% +/- 0.2317% (-0.09 +/- 0.01) seconds user: -2.2071% +/- 0.2308% (-0.09 +/- 0.01) ``` Scanner benchmark with `--string`: ``` msec task-clock:u: -15.0073% +/- 0.2175% (-745.93 +/- 10.81) page-faults:u: -95.0035% +/- 0.0003% (-228024.25 +/- 0.81) cycles:u: -7.7986% +/- 0.2329% (-1558985588.99 +/- 46560962.79) instructions:u: -3.7054% +/- 0.0000% (-1581977447.66 +/- 481.68) branch-misses:u: -0.6880% +/- 0.5818% (-689453.22 +/- 583101.50) seconds time elapsed: -15.0198% +/- 0.2170% (-0.75 +/- 0.01) seconds user: -8.8149% +/- 0.2648% (-0.41 +/- 0.01) seconds sys: -94.1247% +/- 1.6444% (-0.34 +/- 0.01) MarkSweep( old space) goes from 6 to 0 ``` Change-Id: I524a21f488da7df5dc9d2cdf40112b84896ad3e0 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/383324 Reviewed-by: Brian Wilkerson <[email protected]> Reviewed-by: Johnni Winther <[email protected]> Commit-Queue: Jens Johansen <[email protected]>
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See: b/374689139. https://dart-review.googlesource.com/c/sdk/+/390941 is blocking an SDK roll. Root cause: ``` Action threw an exception: type 'ConstructorMember' is not a subtype of type 'ConstructorFragment' in type cast #0 InterfaceTypeImpl.constructors2.<anonymous closure> (package:analyzer/src/dart/element/type.dart:569) #1 MappedListIterable.elementAt (dart:_internal/iterable.dart:435) #2 ListIterator.moveNext (dart:_internal/iterable.dart:364) #3 new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:189) #4 new _GrowableList.of (dart:core-patch/growable_array.dart:150) #5 new List.of (dart:core-patch/array_patch.dart:39) #6 ListIterable.toList (dart:_internal/iterable.dart:224) #7 InterfaceTypeImpl.constructors2 (package:analyzer/src/dart/element/type.dart:570) #8 _Visitor._hasConstConstructorInvocation (package:linter/src/rules/prefer_const_constructors_in_immutables.dart:110) #9 _Visitor.visitConstructorDeclaration (package:linter/src/rules/prefer_const_constructors_in_immutables.dart:58) ``` To verify the fix locally: ``` solo_test_X() async { await assertNoErrorsInCode(r''' class A<T> {} '''); var A = findElement.class_('A').instantiate( typeArguments: [intType], nullabilitySuffix: NullabilitySuffix.none, ); A.constructors2; } ``` Bug: b/374689139 Change-Id: I70034d938d840dc0c3939db27e7116164e4617e9 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/391483 Reviewed-by: Konstantin Shcheglov <[email protected]> Commit-Queue: Phil Quitslund <[email protected]>
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The EchoServer tests occasionally hits what should be an unreachable path.
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