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Niels Lohmann
6b43220a50
The wide-string input adapter (used for std::u16string, std::u32string, std::wstring, and iterators over 2- or 4-byte character types) passed some malformed code units on to the lexer as values that are neither a byte (0x00..0xFF) nor char_traits<char>::eof(). As a result: - A lone UTF-16 surrogate inside true/false/null was accepted if its low byte matched the expected letter, or ended the input silently if it was the last unit. - A high surrogate followed by a unit that is not its low surrogate swallowed that unit; if the swallowed unit was the newline ending a // comment, the comment silently extended over the next line. - Where wint_t is a signed int (macOS, the BSDs), a negative wchar_t collided with char_traits<char>::eof() (ending the input early) or was truncated to its low byte, depending on its value. The UTF-32 helper now converts the code unit to std::uint32_t before the range checks, so a negative unit reaches the same "emit 0xFF" branch already used for code points above U+10FFFF. The UTF-16 helper now peeks at the next unit before consuming it, and emits 0xFF instead of the raw surrogate when no valid pair is found, matching how ill-formed UTF-8 bytes are rejected elsewhere in the lexer. Fixes #5645. Signed-off-by: Niels Lohmann <mail@nlohmann.me>