Message-ID: <49EE9A96.6040900@byu.net>
Date: Tue, 21 Apr 2009 22:18:30 -0600
From: Eric Blake <ebb9@byu.net>
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Subject: Re: [1.7] Updated: cygwin-1.7.0-45
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According to Dave Korn on 4/21/2009 5:57 PM:
>> And better so since sed isn't broken.  It puts EOF into the isblank
>> function and rightly expects that isblank returns 0.
> 
>   I thought the problem was that it puts 0xff into the isblank function and
> gets 1 in some locales where 0xff is an NBSP, if that's not the case I've
> misunderstood the thread so far.

The bug was that isblank(-1) was blindly treated as if were equivalent
with isblank(0xff), which, in some locales, is flat out wrong
(isblank(EOF) should always be 0, even when isblank(0xff) is well-defined
as 1).  Broken apps can't tell the difference between isblank((char)0xff)
and isblank(EOF), but correct apps, like sed, CAN tell the difference
between 0xff and EOF in "int ch = getchar(); isblank(ch)" since getchar()
returns an int containing an unsigned char value (and not a char).

Sed's infinite loop, then, was because of newlib/cygwin's bug - sed
reached the end of the file while trying to skip blanks, but because
isblank() was returning the wrong value for -1, sed thought that EOF was a
blank and kept trying to read the file instead of breaking out of the loop.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9@byu.net
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