Fix incorrect bitshifting and masking in ffi bitfield #10403
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looks correct but defering to @dstogov |
dstogov
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Jan 23, 2023
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Thank you for the comments. I added a test and by doing so I found an additional issue regarding the prefix byte's mask which I fixed as well. |
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When a uint8_t is bitshifted to the left, it is actually promoted to an int. For the current code this has the effect of a wrong sign-extension, and the result will also wrongly become zero when insert_pos >= 32. Fix this by adding an explicit cast. Furthermore, the partial prefix byte mask was computed incorrectly: the byte is already shifted so the mask should not account for the shift.
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dstogov
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Jan 24, 2023
* PHP-8.1: Fix incorrect bitshifting and masking in ffi bitfield (#10403)
dstogov
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Jan 24, 2023
* PHP-8.2: Fix incorrect bitshifting and masking in ffi bitfield (#10403)
Great! Thank you very much. |
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When a uint8_t is bitshifted to the left, it is actually promoted to an int. For the current code this has the effect of a wrong sign-extension, and the result will also wrongly become zero when insert_pos >= 32. Fix this by adding an explicit cast.
Furthermore, the partial prefix byte mask was computed incorrectly: the
byte is already shifted so the mask should not account for the shift.
Note: I found these issues using a static analyser and manually verified that they're real issues.
Travis failure is unrelated to this PR.