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List: kde-core-devel
Subject: Re: Review Request 127866: Oxygen: Fix QCache usage
From: Mark Gaiser <markg85 () gmail ! com>
Date: 2016-05-22 17:53:39
Message-ID: 20160522175339.12876.25013 () mimi ! kde ! org
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This looks much better then the previous version! Good job!
liboxygen/oxygenhelper.h (line 118)
<https://git.reviewboard.kde.org/r/127866/#comment64795>
Is a fifo cache really what you'd want here? I think you would want a LRU cache \
instead.. But yeah, that adds quite a bit complexity.
- Mark Gaiser
On mei 22, 2016, 4:20 a.m., Michael Pyne wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/127866/
> -----------------------------------------------------------
>
> (Updated mei 22, 2016, 4:20 a.m.)
>
>
> Review request for kde-workspace and Hugo Pereira Da Costa.
>
>
> Repository: oxygen
>
>
> Description
> -------
>
> This should mostly complete the QCache fixes I kicked off in a previous RR, 127837. \
> Hugo noted there were many other similar usages, and boy he wasn't kidding! ;) The \
> long story short is that these usages can theoretically cause use-after-free \
> behavior (which can lead to crashes and even undefined behavior if the compiler \
> ever gets smart).
> *NOTE* It is -much- easier to review if you download the diff to your git \
> repository for oxygen and then run "git diff -b" to ignore whitespace changes, \
> particularly for the QPixmap changes.
> For QPixmaps we return values instead of pointers, so we simply make a separate \
> copy to be cached when we do insert. For QColor we return references to values so \
> we *must* return pointers, and those have to be owned by a QCache to avoid \
> memleaks. So I added a helper function to loop until the cache accepts the new \
> entry. TileSets are a similar concern, except those have manual loops since I was \
> uncertain about whether TileSet's copy constructor was the best idea or not.
> This fixes a ton of Coverity issues (59717 - 259733, 259739, 259742 - 259752, \
> 1336154, 1336155) and might be associated with Qt bug 38142 and KDE bug 219055 \
> (which doesn't actually appear to be a dupe of a different bug to me...).
>
> Diffs
> -----
>
> kdecoration/oxygendecohelper.cpp aa75eca
> kstyle/oxygenstyle.cpp e428606
> kstyle/oxygenstylehelper.h 9510a60
> kstyle/oxygenstylehelper.cpp 612ba37
> liboxygen/oxygenhelper.h a6453a0
> liboxygen/oxygenhelper.cpp 4843604
> liboxygen/oxygenshadowcache.cpp 907e586
>
> Diff: https://git.reviewboard.kde.org/r/127866/diff/
>
>
> Testing
> -------
>
> Compiled without warnings, installed and ran `oxygen-demo5 -style oxygen`. Used the \
> GUI Benchmark feature to automatically cycle through all the listed features -- no \
> crashes or obvious rendering errors.
>
> Thanks,
>
> Michael Pyne
>
>
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<div style="font-family: Verdana, Arial, Helvetica, Sans-Serif;">
<table bgcolor="#f9f3c9" width="100%" cellpadding="12" style="border: 1px #c9c399 \
solid; border-radius: 6px; -moz-border-radius: 6px; -webkit-border-radius: 6px;"> \
<tr> <td>
This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/127866/">https://git.reviewboard.kde.org/r/127866/</a>
</td>
</tr>
</table>
<br />
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">This \
looks much better then the previous version! Good job!</p></pre> <br />
<div>
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;"> <thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;"> <a \
href="https://git.reviewboard.kde.org/r/127866/diff/2/?file=465344#file465344line118" \
style="color: black; font-weight: bold; text-decoration: \
underline;">liboxygen/oxygenhelper.h</a> <span style="font-weight: normal;">
(Diff revision 2)
</span>
</th>
</tr>
</thead>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th> <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td> <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">118</font></th> <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span \
class="n">class</span> <span class="n">FIFOCache</span></pre></td> </tr>
</tbody>
</table>
<div style="margin-left: 2em;">
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Is a \
fifo cache really what you'd want here? I think you would want a LRU cache instead.. \
But yeah, that adds quite a bit complexity.</p></pre> </div>
</div>
<br />
<p>- Mark Gaiser</p>
<br />
<p>On mei 22nd, 2016, 4:20 a.m. UTC, Michael Pyne wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="12" style="border: \
1px #888a85 solid; border-radius: 6px; -moz-border-radius: 6px; \
-webkit-border-radius: 6px;"> <tr>
<td>
<div>Review request for kde-workspace and Hugo Pereira Da Costa.</div>
<div>By Michael Pyne.</div>
<p style="color: grey;"><i>Updated mei 22, 2016, 4:20 a.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
oxygen
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">This should mostly complete the QCache fixes I kicked \
off in a previous RR, 127837. Hugo noted there were many other similar usages, and \
boy he wasn't kidding! ;) The long story short is that these usages can theoretically \
cause use-after-free behavior (which can lead to crashes and even undefined behavior \
if the compiler ever gets smart).</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;"><em style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">NOTE</em> It is -much- easier to review if you download the diff to your git \
repository for oxygen and then run "git diff -b" to ignore whitespace changes, \
particularly for the QPixmap changes.</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">For QPixmaps we return \
values instead of pointers, so we simply make a separate copy to be cached when we do \
insert. For QColor we return references to values so we <em style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">must</em> return pointers, and those have to be owned by a QCache to avoid \
memleaks. So I added a helper function to loop until the cache accepts the new entry. \
TileSets are a similar concern, except those have manual loops since I was uncertain \
about whether TileSet's copy constructor was the best idea or not.</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">This fixes a ton of Coverity issues (59717 - 259733, 259739, 259742 - \
259752, 1336154, 1336155) and might be associated with Qt bug 38142 and KDE bug \
219055 (which doesn't actually appear to be a dupe of a different bug to \
me...).</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Compiled without warnings, installed and ran <code \
style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: \
0;line-height: inherit;">oxygen-demo5 -style oxygen</code>. Used the GUI Benchmark \
feature to automatically cycle through all the listed features -- no crashes or \
obvious rendering errors.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>kdecoration/oxygendecohelper.cpp <span style="color: grey">(aa75eca)</span></li>
<li>kstyle/oxygenstyle.cpp <span style="color: grey">(e428606)</span></li>
<li>kstyle/oxygenstylehelper.h <span style="color: grey">(9510a60)</span></li>
<li>kstyle/oxygenstylehelper.cpp <span style="color: grey">(612ba37)</span></li>
<li>liboxygen/oxygenhelper.h <span style="color: grey">(a6453a0)</span></li>
<li>liboxygen/oxygenhelper.cpp <span style="color: grey">(4843604)</span></li>
<li>liboxygen/oxygenshadowcache.cpp <span style="color: grey">(907e586)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/127866/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>
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