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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Libc++ shipped math.h and -isystem breakage"
href="https://bugs.llvm.org/show_bug.cgi?id=33719">33719</a>
</td>
</tr>
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<th>Summary</th>
<td>Libc++ shipped math.h and -isystem breakage
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>4.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>krejzi@email.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
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<p>
<div>
<pre>While compiling Qt 5.9.1, which for some reason uses -isystem /usr/include on
my Linux system, I have noticed the following issue:
clang++ will prepend /usr/include before all system search paths, including
/usr/include/c++/v1, where c++ headers and shipped math.h are located, which
means it will pick math.h from /usr/include (from GNU Glibc) if something
includes cmath (which pulls math.h).
This can be tested using the following example
test.cpp:
#include <cmath>
int main()
{
return (int) isfinite(1);
}
$ clang++ -std=libc++ -std=c++11 test.cpp # all good
$ clang++ -std=libc++ -std=c++11 test.cpp -isystem /usr/include # all hell
breaks loose
/usr/bin/../include/c++/v1/cmath:313:9: error: no member named 'signbit' in the
global namespace; did you mean '__signbit'?
using ::signbit;
~~^
/usr/include/bits/mathcalls.h:375:20: note: '__signbit' declared here
__MATHDECL_1 (int, __signbit,, (_Mdouble_ __value))
^
In file included from test.cpp:1:
/usr/bin/../include/c++/v1/cmath:314:9: error: no member named 'fpclassify' in
the global namespace; did you mean '__fpclassify'?
using ::fpclassify;
~~^
/usr/include/bits/mathcalls.h:371:20: note: '__fpclassify' declared here
__MATHDECL_1 (int, __fpclassify,, (_Mdouble_ __value))
^
and so on...
Linux x86_64, clang 4.0.1 built with libc++ as the default standard library</pre>
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