<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </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 - clang does not define __GNUC_GNU_INLINE__"
   href="https://bugs.llvm.org/show_bug.cgi?id=37784">37784</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>clang does not define __GNUC_GNU_INLINE__
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </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>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Frontend
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>ndesaulniers@google.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llozano@chromium.org, llvm-bugs@lists.llvm.org, manojgupta@google.com, srhines@google.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>In the linux kernel, we prefer to use gnu89 semantics for extern inline
functions.  Writing a feature test for the attribute gnu_inline should be
straightforward, except that gcc did not get __has_attribute until 5.1. 
Instead, older versions of gcc define __GNUC_GNU_INLINE__ if that attribute is
supported.  It seems that clang does not, which makes writing a feature test a
little wonky:

#ifdef __GNUC_GNU_INLINE__
#define __gnu_inline __attribute__((gnu_inline))
#else
#define __gnu_inline
#warning "No gnu inline"
#endif

produces a warning in clang.

We can likely work around this via:

#ifndef __has_attribute         // Optional of course.
#define __has_attribute(x) 0  // Compatibility with non-clang compilers.
#endif

#if defined(__GNUC_GNU_INLINE__) || __has_attribute(gnu_inline)
#define __gnu_inline __attribute__(gnu_inline)
#endif</pre>
        </div>
      </p>


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