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Re: [PATCH][RFC] Avoid table lookup in isascii, isxdigit.
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Paul Eggert <eggert at cs dot ucla dot edu>
- Cc: Rich Felker <dalias at aerifal dot cx>, libc-alpha at sourceware dot org
- Date: Sat, 13 Apr 2013 08:16:48 +0200
- Subject: Re: [PATCH][RFC] Avoid table lookup in isascii, isxdigit.
- References: <20130409115706 dot GA7587 at domone dot kolej dot mff dot cuni dot cz> <20130412204241 dot GK20323 at brightrain dot aerifal dot cx> <51687F17 dot 3070806 at cs dot ucla dot edu>
On Fri, Apr 12, 2013 at 02:39:35PM -0700, Paul Eggert wrote:
> On 04/12/13 13:42, Rich Felker wrote:
> > #define isdigit(c) ((unsigned)(c)-'0'<10)
>
> Unfortunately, this implementation mishandles some
> obscure usages, e.g.,:
>
> double eof = EOF;
> return isdigit (eof);
>
> on systems where the implementation raises a signal
> when converting an out-of-range floating-point value
> to unsigned.
How what I originaly wrote handles this? Even ancient gcc optimizes it
to code above.
To gcc optimizing I found bug gcc 54491 and checked that what I wrote
avoids it.