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The example Fibonacci is not responsive most of the times #23

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DartBot opened this issue Oct 10, 2011 · 2 comments
Closed

The example Fibonacci is not responsive most of the times #23

DartBot opened this issue Oct 10, 2011 · 2 comments
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closed-invalid Closed as we don't believe the reported issue is generally actionable

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DartBot commented Oct 10, 2011

This issue was originally filed by [email protected]


What steps will reproduce the problem?

  1. At dartland.org, choose the example Fibonacci.
  2. Instead of 20, as a parameter for the function Fib, use 50.

What is the expected output? What do you see instead?
I was expecting a numeric output generated by the function. Instead, the page freezes or crashes.

What version of the product are you using? On what operating system?
n/a. Google Chrome on Windows 7

Please provide any additional information below.

@DartBot
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DartBot commented Oct 10, 2011

This comment was originally written by [email protected]


Fibonacci grows exponentially as a geometric power, the difference between 30 and 50 is orders of magnitude, and thus of course you don't see the result because it takes a very long time to compute. Try learning how to open the Task Manager and checking the CPU usage or write a print statement to find out what fibonacci you are on.
What a stupid bug report... trash it.

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DartBot commented Oct 11, 2011

This comment was originally written by [email protected]


Um, yes, the example code is the recursive algorithm, which blows up quickly for n>35. In fact, Google App Engine system status page uses this algorithm as a compact way to tax the CPU for measurement purposes. Personally, the example bothers me because it's too verbose. With Dart, you can easily compute the nth Fibonacci # in exactly 34 characters (granted, spacing is a bit arbitrary):

f(n) => n<2 ? n : f(n-2) + f(n-1);


Added Invalid label.

@DartBot DartBot added Type-Defect closed-invalid Closed as we don't believe the reported issue is generally actionable labels Oct 11, 2011
copybara-service bot pushed a commit that referenced this issue Jul 21, 2023
Here's a minimal repro that this CL fixes:

`ui.dart`

```dart
library dart.ui;

import 'dart:ffi';

part 'foo.dart';
```

`foo.dart`

```dart
part of dart.ui;

@Native<Void Function()>(symbol: 'foo_func', isLeaf: true)
external void foo_func();
```

When compiling with `compile_platform.dart` with `--target=dart2wasm`, the following error appears:


```
Unhandled exception:
Verification error: Target=wasm, VerificationStage.afterModularTransformations: Invalid location with target 'wasm' on FunctionNode() (FunctionNode): RangeError (offset): Invalid value: Not in inclusive range 0..56: 91
Context: 'foo_func_$import'.
Node: 'FunctionNode()'.
#0      VerificationErrorListener.reportError (package:kernel/verifier.dart:81:5)
#1      VerifyingVisitor.problem (package:kernel/verifier.dart:222:14)
#2      VerifyingVisitor._getLocation (package:kernel/verifier.dart:1361:7)
#3      VerifyingVisitor._hasLocation (package:kernel/verifier.dart:1370:26)
#4      VerifyingVisitor.getSameLibraryLastSeenTreeNode (package:kernel/verifier.dart:1342:28)
#5      VerifyingVisitor.localContext (package:kernel/verifier.dart:1382:24)
#6      VerifyingVisitor.defaultDartType (package:kernel/verifier.dart:1491:41)
#7      Visitor.visitVoidType (package:kernel/visitor.dart:1309:37)
#8      VoidType.accept (package:kernel/ast.dart:11190:42)
#9      FunctionNode.visitChildren (package:kernel/ast.dart:3919:16)
#10     VerifyingVisitor.visitChildren (package:kernel/verifier.dart:259:10)
#11     VerifyingVisitor.visitWithLocalScope (package:kernel/verifier.dart:266:5)
#12     VerifyingVisitor.visitFunctionNode (package:kernel/verifier.dart:721:5)
#13     FunctionNode.accept (package:kernel/ast.dart:3908:38)
#14     VerifyingVisitor.visitProcedure (package:kernel/verifier.dart:620:19)
#15     Procedure.accept (package:kernel/ast.dart:3311:40)
#16     visitList (package:kernel/ast.dart:14488:14)
#17     Library.visitChildren (package:kernel/ast.dart:591:5)
#18     VerifyingVisitor.visitChildren (package:kernel/verifier.dart:259:10)
#19     VerifyingVisitor.defaultTreeNode (package:kernel/verifier.dart:196:5)
#20     TreeVisitor.visitLibrary (package:kernel/visitor.dart:503:35)
#21     VerifyingVisitor.visitLibrary (package:kernel/verifier.dart:367:11)
#22     Library.accept (package:kernel/ast.dart:577:38)
#23     visitList (package:kernel/ast.dart:14488:14)
#24     Component.visitChildren (package:kernel/ast.dart:14320:5)
#25     VerifyingVisitor.visitChildren (package:kernel/verifier.dart:259:10)
#26     VerifyingVisitor.visitComponent (package:kernel/verifier.dart:342:7)
#27     Component.accept (package:kernel/ast.dart:14313:38)
#28     VerifyingVisitor.check (package:kernel/verifier.dart:171:15)
#29     verifyComponent (package:kernel/verifier.dart:69:20)
...
```

The issue seems to be that after doing this native transformation, the node's `fileUri` references the enclosing library (`ui.dart` above), but the `node.location` references the actual source file (`foo.dart` above) indirectly through `node.fileOffset`.

This ends up being an issue when compiling the platform dill in Google3,   but I didn't look into why `flutter build web --wasm` isn't broken.

Internal bug: b/292172146

Change-Id: I2b8d7d215b2c36354860257ce651d50168e9523d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/315360
Reviewed-by: Ömer Ağacan <[email protected]>
Commit-Queue: Jia Hao Goh <[email protected]>
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