Fix repeatString overflow test on 32-bit platforms#2680
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jandubois wants to merge 1 commit intomikefarah:masterfrom
Open
Fix repeatString overflow test on 32-bit platforms#2680jandubois wants to merge 1 commit intomikefarah:masterfrom
jandubois wants to merge 1 commit intomikefarah:masterfrom
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The test literal "ab" * 4611686018427387904 (2^62) exceeds MaxInt32,
so parseInt rejects it before the size guard runs. Compute the count
with 1 << (bits.UintSize - 2) to yield 2^30 on 32-bit and 2^62 on
64-bit. Both values, when doubled by len("ab"), wrap past MaxInt and
bypass a naive len*count guard, exercising the division-safe check
added in mikefarah#2644.
Signed-off-by: Jan Dubois <jan@jandubois.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Thanks!
Probably just running on x86 on CI should suffice for detecting regressions, but this works as-is. |
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The test literal "ab" * 4611686018427387904 (2^62) exceeds MaxInt32, so parseInt rejects it before the size guard runs. Compute the count with 1 << (bits.UintSize - 2) to yield 2^30 on 32-bit and 2^62 on 64-bit. Both values, when doubled by len("ab"), wrap past MaxInt and bypass a naive len*count guard, exercising the division-safe check added in #2644.
Ref #2644 (comment)
I've verified that the modified test case still triggers the original panic on 64-bit platforms unless the fix from #2644 is applied.
I've also verified that this change fixes cross-compilation to 32-bit mode.
I am NOT able to test the 32-bit binary itself, so I don't know if it will pass tests, and I don't know if this code will still trigger the original bug. From a pure math perspective it should.