<html>
    <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 --- - warning when comparing enum with constant in C"
   href="https://llvm.org/bugs/show_bug.cgi?id=27680">27680</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>warning when comparing enum with constant in C
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>3.8
          </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>

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

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

        <tr>
          <th>Reporter</th>
          <td>pgrunt@redhat.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>When compiling C code:

typedef enum {
    A=0,
} my_enum;

int f(my_enum x) {
    if (x <= 1)
        return -1;
    return 0;
}

with -Wall a -Wtautological-constant-out-of-range-compare warning is produced.
However changing code to:

typedef enum {
    A=1,
} my_enum;

int f(my_enum x) {
    if (x <= 1)
        return -1;
    return 0;
}

No warning is produced. So there seems to be some inconsistency.
Personally I would remove the warning for enum comparison when compiling C code
at all - in C enums and ints can be mixed.</pre>
        </div>
      </p>
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