fix: handle match_mask == 0 in NEON ctzll to avoid undefined behavior#83
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lalinsky wants to merge 1 commit intonodejs:mainfrom
Open
fix: handle match_mask == 0 in NEON ctzll to avoid undefined behavior#83lalinsky wants to merge 1 commit intonodejs:mainfrom
lalinsky wants to merge 1 commit intonodejs:mainfrom
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When all 16 bytes match the allowed range, match_mask becomes 0 after
the bitwise NOT. Calling __builtin_ctzll(0) is undefined behavior.
The code expects match_len == 16 when all bytes match (so the branch
is skipped and p += 16 continues the loop), but this relied on
ctzll(0) returning 64, which is not guaranteed.
Example panic on macOS ARM64:
thread 44856 panic: passing zero to ctz(), which is not a valid argument
src/llhttp/llhttp.c:2654:21: in llhttp__internal__run
match_len = __builtin_ctzll(match_mask) >> 2;
^
Fix by explicitly checking for match_mask == 0 and setting match_len = 16.
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When all 16 bytes match the allowed range,
match_maskbecomes 0 after the bitwise NOT. Calling__builtin_ctzll(0)is undefined behavior.The code expects
match_len == 16when all bytes match (so the branch is skipped andp += 16continues the loop), but this relied onctzll(0)returning 64, which is not guaranteed.Example panic on macOS ARM64:
Fix by explicitly checking for
match_mask == 0and settingmatch_len = 16.Related: lalinsky/dusty#14