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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Clang hangs with Class string literal comparison"
href="http://llvm.org/bugs/show_bug.cgi?id=15257">15257</a>
</td>
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<tr>
<th>Summary</th>
<td>Clang hangs with Class string literal comparison
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dustin.clark@emerson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Hi guys, this is kind of a weird issue discovered yesterday as a result of
updating a CI server with the latest version of Xcode.
I've generalized what the team member was trying to do and while it's not
correct/ideal -- I don't imagine it's intended to cause a hangup.
$ cat bug.m
int main(int argc, const char * argv[])
{
NSString *string = [[NSString alloc] init];
if (string.class == @"NSString") NSLog(@"Foo");
return 0;
}
With the older version:
$ clang --version
Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix
$ clang -framework Cocoa bug.m -o bug
$
With the newer version:
$
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
--version
Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix
$
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
-framework Cocoa bug.m -o bug
bug.m:6:19: warning: direct comparison of a string literal has undefined
behavior [-Wobjc-string-compare]
if (string.class == @"NSString") NSLog(@"Foo");
^ ~~~~~~~~~~~
And now clang is, indefinitely, hanging at 100% CPU.
I've fixed the issue on our end by having them correctly use isKindOfClass or
NSStringFromClass :) -- but I thought I would file the bug incase it's unknown.
Thanks for your time -- and I sincerely apologize if this is a duplicate issue.
Regards,
Dusty</pre>
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