From: DJ Delorie Subject: Re: some unusual errors 22 Sep 1998 16:13:54 -0400 Message-ID: <36080502.41C6@delorie.com> References: <9809211418.AA12875@vviuh221.vvi.com> <199809212009.NAA00026.cygnus.gnu-win32@aleph.ssd.hal.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (X11; I; IRIX 5.3 IP22) J. J. Farrell wrote: > isspace() is prototyped as isspace(int); if the caller > were using the function version, then the prototype would > be effective, and the char would have been silently and > correctly widened to an int. No, the char would have been silently and INcorrectly widened to a *signed* int, resulting in a range of values of -128..127. That is not the legal range of values for the is*() functions. The legal range of values for is*() is 0..255 and EOF. The automatic widening of a [default signed] char results in signed int values in the range -128..127. You cannot rely on the automatic widening to give correct results. On a side note, using a signed char as the input makes it impossible to tell the difference between character 255 and the traditional EOF value of -1, as both have the same bit pattern (0xff) when stored in a signed char variable. Because there are 257 legal parameter values for is*(), an 8-bit variable is simply too small to represent them without loss or inaccuracy.