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Re: signed vs unsigned char in coding.h

From: Chetan Pandya
Subject: Re: signed vs unsigned char in coding.h
Date: Fri, 20 Feb 2009 13:29:25 -0800 (PST)

--- On Fri, 2/20/09, Dan Nicolaescu <address@hidden> wrote:
> struct coding_system in coding.h contains this:
>       char *safe_charsets;
> and coding.c has this:
> #define SAFE_CHARSET_P(coding, id)      \
>   ((id) <= (coding)->max_charset_id     \
>    && (coding)->safe_charsets[id] >= 0)
> on some platforms "char" is unsigned by default,
> so the above >=0
> comparison is always true.
> What is the intention here, should safe_charsets be defined
> as "signed char" ?

It looks like there are more things needed here. Since the safe_charsets is 
part of a string, it makes sense to declare it as unsigned char and compare it 
to 255.

However, when in coding.c:9298 this is initialized with 
  safe_charsets = Fmake_string (make_number (max_charset_id + 1),
                                make_number (255));
This also has problems since it tries to create a string with a character that 
is not ASCII_CHAR_P. Wouldn't it make sense to create with ascii char and then 
replace all with 255 instead?


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