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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Fix -Wparentheses warning with GCC 5 in SaturatedArithmetic.h"
href="https://bugs.webkit.org/show_bug.cgi?id=143457">143457</a>
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<th>Summary</th>
<td>Fix -Wparentheses warning with GCC 5 in SaturatedArithmetic.h
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<th>Classification</th>
<td>Unclassified
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<th>Product</th>
<td>WebKit
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<th>Version</th>
<td>528+ (Nightly build)
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>Minor
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>Web Template Framework
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>mcatanzaro@igalia.com
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<pre>When building with GCC 5, I can't see any real warnings, because this buddy gets printed 3000 times [1] during compilation:
../../Source/WTF/wtf/SaturatedArithmetic.h: In function ‘bool signedAddOverflows(int32_t, int32_t, int32_t&)’:
../../Source/WTF/wtf/SaturatedArithmetic.h:49:29: warning: suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’ to ‘~’ [-Wparentheses]
return !((ua ^ ub) >> 31) & (uresult ^ ua) >> 31;
^
Clang has had this same warning for a while. The warning is spurious [2], but it's a good warning so let's placate it rather than disable. Two solutions:
Add extra parentheses: return (!((ua ^ ub) >> 31)) & (uresult ^ ua) >> 31;
Note that is equivalent to the original code [3].
Another option is to use &&:
!((ua ^ ub) >> 31) && (uresult ^ ua) >> 31;
That looks better to me, since there are fewer parentheses and it avoids the confusing/unnecessary [3] mask.
[1] I just made that up, but it doesn't feel like an unreasonable guess.
[2] & and && both have the same precedence relative to !
[3] Provided I've squinted at this long enough.</pre>
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