Andrey Chernov <a...@nagual.pp.ru> writes: > "Simon L. Nielsen" <si...@freebsd.org> writes: > > Acording to the manual page and the C standard book I have, > > isdigit() takes an int for an argument, so why change this? > "The value of the argument must be representable as an unsigned char or > the value of EOF." > > Signed char (automatically casted to int in expression even without direct > (int) cast) passed to any ctype macro potentically may cause a lot of > problems, such as: incorrect char class detection or even core dump in > some systems. > > This is due to automatic sign extension of 8bit (if present).
To put it more clearly: - The is*() functions expect an int for the same reason fgetc() returns one: a char alone can't represent all possible char values *plus* EOF. - In most 8-bit locales, there are valid characters outside the 0-127 range. When stored in a signed char, such characters are represented as negative values. When that signed char is promoted to a signed int, the negative values remain negative instead of being converted to the correct positive value. - This would not be a problem if C distinguished between a character (unsigned) and a "short short int" (signed). - The core dump ache refers to can occur with a naïve implementation that uses a lookup table and checks for EOF, but not for other negative values. DES -- Dag-Erling Smørgrav - d...@des.no _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
