Re: Question about -Wchar-subscripts
In the last episode (Oct 03), Larry Lile said: ...we get scores of warnings about using characters as subscripts to an array (-Wchar-subscripts), which generates so much noise as to mask real warnings burried within. Therefore, I would like to suppress this warning unless someone can explain why using a char as an array subscript is in any way an illegitimate thing to do. As far as I can tell, getting rid of the warning by changing the code would require adding a large number of frivolous casts to scores of source files... So why is using a "char" as an array subscript wrong? I had always avoided it because the compiler complained and that was good enough for me. Because your char value could be negative and end up referencing memory before your array start. Mainly a problem with the ctype macros and high-ascii characters. -- Dan Nelson [EMAIL PROTECTED] To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: Question about -Wchar-subscripts
In the last episode (Oct 03), Larry Lile said: ...we get scores of warnings about using characters as subscripts to an array (-Wchar-subscripts), which generates so much noise as to mask real warnings burried within. Therefore, I would like to suppress this warning unless someone can explain why using a char as an array subscript is in any way an illegitimate thing to do. As far as I can tell, getting rid of the warning by changing the code would require adding a large number of frivolous casts to scores of source files... So why is using a "char" as an array subscript wrong? I had always avoided it because the compiler complained and that was good enough for me. Because your char value could be negative and end up referencing memory before your array start. Mainly a problem with the ctype macros and high-ascii characters. That's an interesting reason... any variable can be negative (well, except for the unsigned types...) - what's so interesting about `char'? Is it simply ctype macros that are the concern, or something "bigger"? - Dave R. - To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: Question about -Wchar-subscripts
- Original Message - From: "Dan Nelson" [EMAIL PROTECTED] To: "Larry Lile" [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 03, 2000 9:49 PM Subject: Re: Question about -Wchar-subscripts In the last episode (Oct 03), Larry Lile said: ...we get scores of warnings about using characters as subscripts to an array (-Wchar-subscripts), which generates so much noise as to mask real warnings burried within. Therefore, I would like to suppress this warning unless someone can explain why using a char as an array subscript is in any way an illegitimate thing to do. As far as I can tell, getting rid of the warning by changing the code would require adding a large number of frivolous casts to scores of source files... So why is using a "char" as an array subscript wrong? I had always avoided it because the compiler complained and that was good enough for me. Because your char value could be negative and end up referencing memory before your array start. Mainly a problem with the ctype macros and high-ascii characters. How about unsigned char? Could that be used for index? Leif To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: Question about -Wchar-subscripts
Robert Nordier [EMAIL PROTECTED] wrote: Thomas David Rivers wrote: So why is using a "char" as an array subscript wrong? I had always avoided it because the compiler complained and that was good enough for me. Because your char value could be negative and end up referencing memory before your array start. Mainly a problem with the ctype macros and high-ascii characters. That's an interesting reason... any variable can be negative (well, except for the unsigned types...) - what's so interesting about `char'? Is it simply ctype macros that are the concern, or something "bigger"? What's interesting about char is that it's implementation defined whether "plain" char is the equivalent of "signed char" or "unsigned char" (or even something else). So, given an 8-bit, two's complement implementation of char, the statement char i = 128; may cause 'i' to end up as -128 or 128, for example. An implementation-defined value to your subscript is almost never useful, so this kind of behavior does warrant a warning. You'll notice gcc doesn't warn if explicitly signed or unsigned chars are used as subscripts, as then there is no uncertainty. -- Robert Nordier Ah - yes! That makes perfect sense... when you consider that `char' all alone can be signed or unsigned... Thanks for the explanation! - Dave Rivers - To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
