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    <head>
      <base href="https://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 --- - Warn about overload resolution with forward-declared types?"
   href="https://llvm.org/bugs/show_bug.cgi?id=25350">25350</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Warn about overload resolution with forward-declared types?
          </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>-New Bugs
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>hans@chromium.org
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, nicolasweber@gmx.de
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Consider the following:

s.h:

  struct S {};
  struct T : S {};

a.cc:

  #if X
  // Forward declarations, for speed:
  struct S;
  struct T;
  #else
  // Just include it, for clarity:
  #include "s.h"
  #endif

  void f(void*);
  void f(S*);

  void surprise(T *t) { f(t); } // Which f gets called?


Depending on the value of X, i.e. whether we're including s.h or forward
declaring S and T, the call in surprise() will be bound to a different
function.

Could we warn that overload resolution for the call to f is based on an
incomplete type?

(Inspired by an example from:
<a href="http://google.github.io/styleguide/cppguide.html#Forward_Declarations">http://google.github.io/styleguide/cppguide.html#Forward_Declarations</a>)</pre>
        </div>
      </p>
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