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Exception text appears in output in dartfuzz #36916

aartbik opened this issue May 9, 2019 · 1 comment


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commented May 9, 2019

The following output divergence:

KBC-CMP-ReleaseX64 - AOT-ReleaseX64: !DIVERGENCE! 1.12:180357858 (output=true)

seems due to subtle difference in the reported exception text. However, these strings should not be compared by dartfuzz in the first place. What is going on?

< RangeError (index): Invalid value: Not in range 0..2, inclusive: -10
> RangeError (length): Invalid value: Not in range 0..2, inclusive: -10

@aartbik aartbik self-assigned this May 9, 2019


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commented May 9, 2019

This is actually hilarious. DartFuzz never introduces the catch (e) variable in its scope to avoid exactly situations like this. However, the math constant "const double e = 2.718281828459045" can be used by the fuzzer, causing an unintentional use of the exception parameter!

   catch (e) {
        var6 ??= var6;
        print(((foo2(fld0_3, 0.8970104855514572, ((!((var1 ? false : true))) ? Int32x4.wzxz : var2))).isNaN ? ((Map.from(Map.of(fld0_0))).isEmpty ? foo2({ 27 : '9En', 24 : 'Mt', 28 : '', 63 : '-Xycx5', 76 : '\u2665BB+B!' }, (0.5074121780321523 + var3), var5[var0]) : var3) : e));

dart-bot pushed a commit that referenced this issue May 9, 2019

[dart/fuzzer] rename exception parameter
catch (e) had a very interesting shadowing
with math's constant e, which unintentionally
allowed exeption text to enter the divergence
mechanism; here we were fuzzing the fuzzing
really :-)


Change-Id: Ie5cd61755ea61921b903684532d404f4dc734edd
Reviewed-by: Alexander Markov <>
Commit-Queue: Aart Bik <>

@aartbik aartbik closed this May 9, 2019

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