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    <head>
      <base href="http://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - cmath: compile failure with custom fabs in std namespace"
   href="http://llvm.org/bugs/show_bug.cgi?id=18176">18176</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>cmath: compile failure with custom fabs in std namespace
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libc++
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>FreeBSD
          </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>

        <tr>
          <th>Component</th>
          <td>All Bugs
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>hhinnant@apple.com
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>amdmi3@amdmi3.ru
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=11687" name="attach_11687" title="Fix">attachment 11687</a> <a href="attachment.cgi?id=11687&action=edit" title="Fix">[details]</a></span>
Fix

When fabs() overload for custom type is added to std namespace, cmath won't
compile. Example code:

% cat test.cc
struct mytype {
};

namespace std {
    mytype fabs(const mytype& a) {
        return mytype();
    }
}

#include <cmath>

int main() {
    mytype a;
    a = std::fabs(a);

    return 0;
}
% clang++ test.cc
In file included from test.cc:10:
/usr/include/c++/v1/cmath:664:35: error: no matching function for call to
'fabs'
abs(double __x) _NOEXCEPT {return fabs(__x);}
                                  ^~~~
4.cc:5:9: note: candidate function not viable: no known conversion from
'double' to 'const mytype' for 1st argument
        mytype fabs(const mytype& a) {
               ^
1 error generated.

Fix is attached. Similar fix may be needed for other functions from global
namespace.</pre>
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