Review Request 127488: Fix usage of std::isprint() function

[Dominik Haumann]

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https://git.reviewboard.kde.org/r/127488/#review93946
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Btw: If you think QChar::isPrint() is a better choice [1], I'm happy to update the review request accordingly.

[1] http://doc.qt.io/qt-5/qchar.html#isPrint-1

- Dominik Haumann


On March 24, 2016, 9:06 p.m., Dominik Haumann wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/127488/
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> 
> (Updated March 24, 2016, 9:06 p.m.)
> 
> 
> Review request for KDE Frameworks.
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> Bugs: 357341
>     https://bugs.kde.org/show_bug.cgi?id=357341
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> Repository: kcodecs
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> Description
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> With the patch in review request https://git.reviewboard.kde.org/r/127486/ I get another crash when loading the attached file in bug https://bugs.kde.org/show_bug.cgi?id=360797
> 
> The issue is the call if isprint(int): Accoring to http://en.cppreference.com/w/cpp/string/byte/isprint
> "the behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF."
> 
> In this case, casting the char to an int results "-31", which is clearly not representable as *unsigned* char. Hence, we indeed hit the "undefined behavior" and get a crash.
> 
> This patch therefore
> - casts the char to an int first
> - and then checks whether the int it non-negative
> - only then, isprint() is called.
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> 
> Diffs
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>   src/probers/UnicodeGroupProber.cpp 1d86f08 
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> Diff: https://git.reviewboard.kde.org/r/127488/diff/
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> Testing
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> Kate/Kwrite launch without crash.
> Unit tests still pass.
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> 
> Thanks,
> 
> Dominik Haumann
> 
>

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