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    <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 - Attribute names enclosed by __ are sometimes rejected"
   href="https://bugs.llvm.org/show_bug.cgi?id=34319">34319</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Attribute names enclosed by __ are sometimes rejected
          </td>
        </tr>

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

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

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </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>sebastian.huber@embedded-brains.de
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>From the GCC documentation we have

<a href="https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute-Syntax">https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute-Syntax</a>

"You may optionally specify attribute names with ‘__’ preceding and following
the name. This allows you to use them in header files without being concerned
about a possible macro of the same name. For example, you may use the attribute
name __noreturn__ instead of noreturn."

It would be nice if this is also supported by clang, e.g. for use in standard C
library header files. We have for example:

void f0(void) __attribute__((noreturn));
void f1(void) __attribute__((__noreturn__));
void f2(int *l) __attribute__((exclusive_lock_function(*l)));
void f3(int *l) __attribute__((__exclusive_lock_function__(*l)));

Which yields:

clang -c test.c
test.c:4:61: error: use of undeclared identifier 'l'
void f3(int *l) __attribute__((__exclusive_lock_function__(*l)));
                                                            ^
1 error generated.</pre>
        </div>
      </p>


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