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Niels Lohmann
1c6ca81b8a
The "ill-formed: wrong fourth byte" SECTIONs in unit-unicode3.cpp, unit-unicode4.cpp, and unit-unicode5.cpp guarded their loop with a check on byte3 instead of byte4. Since the enclosing loop already restricts byte3 to its valid range, the guard was always true and the section's "continue" fired unconditionally, so check_utf8string()/check_utf8dump() were never actually invoked for a malformed fourth byte. Fixing the guard naively (byte3 -> byte4) would also have swept the full byte2 x byte3 combinatorics for every byte4 value, adding millions of redundant iterations: the lexer validates continuation bytes strictly in sequence with early exit (see next_byte_in_range() in lexer.hpp), so once byte2/byte3 are within their valid range, the byte4 outcome does not depend on which valid byte2/byte3 values were chosen. Instead, byte2 and byte3 are now held to a small hedge of representative valid prefixes (range corners plus a midpoint) while byte4 is still swept exhaustively over its full 0x00-0xFF range, since that is the actual property under test. Also fixed the garbled "skip fourth second byte" comment in unit-unicode3.cpp. Verified offline: before the fix, the "wrong fourth byte" subcase executes 0 assertions in all three files (proving it was dead code); after the fix, it executes 11520 (unicode3), 34560 (unicode4), and 11520 (unicode5) assertions, and a deliberately reintroduced bug in the lexer's byte4 range check causes it to fail (proving it is now meaningful). Total per-file assertion counts grow by the same small amounts, not by millions, and all other sections in these files still pass unchanged. Fixes #5416 Signed-off-by: Niels Lohmann <mail@nlohmann.me>