ASC::GUTHERY%slb-test.csnet@relay.cs.net (03/31/87)
C Guri: In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the grounds that it's a brain-damaged version of '\x00'. This is what Microsoft's support group said when I reported what I thought was a bug. I claim that '\x' is a perfectly fine representation of the character x and should have value 120 base 10. How sayeth INFO-C?
gwyn@brl-smoke.UUCP (03/31/87)
In article <6570@brl-adm.ARPA> @relay.cs.net> writes: >C Guri: >In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the >grounds that it's a brain-damaged version of '\x00'. This is what >Microsoft's support group said when I reported what I thought was a >bug. I claim that '\x' is a perfectly fine representation of the >character x and should have value 120 base 10. How sayeth INFO-C? Future ANSI-conforming C compilers will treat '\xNNN' (where NNN are 1 to 3 hexadecimal digits) as the hex code for a character. '\x' is not supposed to be a valid hex code, but we don't say what it is; definitely it's not guaranteed to be just the letter 'x'. By the way, I intend to submit an improved proposal for removing the limit to the number of bits supported for \x. The one I presented at the very end of the last meeting ran into at least one valid objection (I had also proposed extending the \0 constants, which can cause problems with existing code that uses embedded NULs). So, basically, MicroSoft is right, except it would be nicer if they would diagnose the case of missing NNN after the \x.
ron@brl-sem.UUCP (04/01/87)
In article <6570@brl-adm.ARPA>, @relay.cs.net> writes: > In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the > grounds that it's a brain-damaged version of '\x00'. This is what > Microsoft's support group said when I reported what I thought was a > bug. I claim that '\x' is a perfectly fine representation of the > character x and should have value 120 base 10. How sayeth INFO-C? Neither \x meaning 0 nor \x meaning 'x' is correct. There is no meaning to \x and those who use it are asking for trouble. By your own admission \n should be the character n which we all know is not true.
dlnash@ut-ngp.UUCP (04/01/87)
In article <705@brl-sem.ARPA>, ron@brl-sem.ARPA (Ron Natalie <ron>) writes: > In article <6570@brl-adm.ARPA>, @relay.cs.net> writes: > > > In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the > > grounds that it's a brain-damaged version of '\x00'. This is what > > Microsoft's support group said when I reported what I thought was a > > bug. I claim that '\x' is a perfectly fine representation of the > > character x and should have value 120 base 10. How sayeth INFO-C? > > Neither \x meaning 0 nor \x meaning 'x' is correct. There is no meaning > to \x and those who use it are asking for trouble. By your own admission > \n should be the character n which we all know is not true. K&R p.181: "If the character following a backslash is not one of those specified [the specified characters are n, t, b, r, f, \, ', and ddd (three octal digits) -ed.], the backslash is ignored." Don Nash UUCP: ...!{ihnp4, allegra, seismo!ut-sally}!ut-ngp!dlnash ARPA: dlnash@ngp.UTEXAS.EDU BITNET: CCEU001@UTADNX, DLNASH@UTADNX TEXNET: UTADNX::CCEU001, UTADNX::DLNASH
law@qtc.UUCP (04/01/87)
In article <6570@brl-adm.ARPA> @relay.cs.net> writes: >bug. I claim that '\x' is a perfectly fine representation of the >character x and should have value 120 base 10. How sayeth INFO-C? Kernighan and Ritchie, pg 181: If the character following a backslash is not one of those specified [in the table of valid escape sequences], the backslash is ignored. ^^^^^^^^^^^^^^^^^^^^^^^^ No more authoritative source exists on the planet (8-). -- "A man hears what he wants to hear and disregards the rest" Larry Westerman Quantitative Technology Corporation Beaverton OR 503-626-3081 ...verdix! or ...sequent! qtc!law
amos@instable.UUCP (04/01/87)
According to K&R (p. 180), if the character following \ is not
one of the special escape sequences, the \ is ignored.
H&S's new C Manual (P.20-22) define a character constant's escape
sequence as \ followed by one of: b t n v f r ' " Anything else
does not constitute a valid escape sequence and should be, therefore,
illegal (or at least undefined).
--
Amos Shapir
National Semiconductor (Israel)
6 Maskit st. P.O.B. 3007, Herzlia 46104, Israel Tel. (972)52-522261
amos%nsta@nsc.com {hplabs,pyramid,sun,decwrl} 34.48'E 32.10'Ndjfiander@watnot.UUCP (04/01/87)
>> In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the >> grounds that it's a brain-damaged version of '\x00'. This is what >> Microsoft's support group said when I reported what I thought was a >> bug. I claim that '\x' is a perfectly fine representation of the >> character x and should have value 120 base 10. How sayeth INFO-C? > >Neither \x meaning 0 nor \x meaning 'x' is correct. There is no meaning >to \x and those who use it are asking for trouble. By your own admission >\n should be the character n which we all know is not true. I hate to say this, the first of you is more right. According to K&R (which admittedly may no longer be correct) if a '\' is followed by something which is not a valid escape sequence, the '\' is ignored, so the first posting has a valid complaint. This came up here with one of the University's C compilers. They changed it to react in the K&R manner, but give a compile time warning that something was wrong. I tend to agree that '\x' is an 'x' and not a 0. If I wanted 0 then I would say '\x00' (well '\0'). -- "I don't want to achieve immortality through my work. I want to achieve immortality through not dying" - Woody Allen UUCP : {allegra,ihnp4,decvax,utzoo,clyde}!watmath!watnot!djfiander CSNET : djfiander%watnot@waterloo.CSNET
drw@cullvax.UUCP (04/02/87)
C Guri:@relay.cs.net> writes: > In the Microsoft C compiler V4.0, '\x' is compiled as 0 on the > grounds that it's a brain-damaged version of '\x00'. This is what > Microsoft's support group said when I reported what I thought was a > bug. I claim that '\x' is a perfectly fine representation of the > character x and should have value 120 base 10. How sayeth INFO-C? Well, according to the ANSI draft standard, it's invalid. Dale -- Dale Worley Cullinet Software UUCP: ...!seismo!harvard!mit-eddie!cullvax!drw ARPA: cullvax!drw@eddie.mit.edu Un*x (a generic name for a class of OS's) != Unix (AT&T's brand of such)
gwyn@brl-smoke.UUCP (04/03/87)
In article <272@qtc.UUCP> law@qtc.UUCP (Larry Westerman) writes: >Kernighan and Ritchie, pg 181: >No more authoritative source exists on the planet (8-). If you happen to be living back in 1978. C has evolved considerably since then.
cmcmanis@sun.UUCP (04/04/87)
I always though that if \0nnn created an octal constant then
\0xnnn should be used to create a hex constant. It would make
parsing the \0 case a little tougher but to me at least it seems
logical.
--
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.geller@eli.UUCP (04/05/87)
In article <5719@brl-smoke.ARPA>, gwyn@brl-smoke.ARPA (Doug Gwyn ) writes: > In article <272@qtc.UUCP> law@qtc.UUCP (Larry Westerman) writes: > >Kernighan and Ritchie, pg 181: > >No more authoritative source exists on the planet (8-). > > If you happen to be living back in 1978. > C has evolved considerably since then. Now don't jump to conclusions. The planet wasn't specified. David Geller D.C.