<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 --- - missing default argument promotion"
   href="https://llvm.org/bugs/show_bug.cgi?id=28046">28046</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>missing default argument promotion
          </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>normal
          </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>vries@gcc.gnu.org
          </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>Consider test.c, compiled with -std=c99:
...
extern void foo();

void bar() {
  foo(1, 2);
}

void foo(d, e)
     int d;
     unsigned int e;
{}

void bar2() {
  foo(3, 4);
}
...

With -ast-dump we get:
...
|-FunctionDecl 0xb90bd38 <test.c:62:1, col:17> col:13 used foo 'void ()' extern
|-FunctionDecl 0xb957990 <line:64:1, line:66:1> line:64:6 bar 'void ()'
| `-CompoundStmt 0xb957b30 <col:12, line:66:1>
|   `-CallExpr 0xb957af0 <line:65:3, col:11> 'void'
|     |-ImplicitCastExpr 0xb957ad8 <col:3> 'void (*)()'
<FunctionToPointerDecay>
|     | `-DeclRefExpr 0xb957a48 <col:3> 'void ()' Function 0xb90bd38 'foo'
'void ()'
|     |-IntegerLiteral 0xb957a70 <col:7> 'int' 1
|     `-IntegerLiteral 0xb957a90 <col:10> 'int' 2
|-FunctionDecl 0xb957ca0 prev 0xb90bd38 <line:68:1, line:71:2> line:68:6 used
foo 'void (int, unsigned int)'
| |-ParmVarDecl 0xb957b60 <line:69:6, col:10> col:10 d 'int'
| |-ParmVarDecl 0xb957bd0 <line:70:6, col:19> col:19 e 'unsigned int'
| `-CompoundStmt 0xb957d68 <line:71:1, col:2>
`-FunctionDecl 0xb957da0 <line:73:1, line:75:1> line:73:6 bar2 'void ()'
  `-CompoundStmt 0xb957f30 <col:13, line:75:1>
    `-CallExpr 0xb957ed8 <line:74:3, col:11> 'void'
      |-ImplicitCastExpr 0xb957ec0 <col:3> 'void (*)()'
<FunctionToPointerDecay>
      | `-DeclRefExpr 0xb957e58 <col:3> 'void ()' Function 0xb957ca0 'foo'
'void (int, unsigned int)'
      |-IntegerLiteral 0xb957e80 <col:7> 'int' 3
      `-ImplicitCastExpr 0xb957f18 <col:10> 'unsigned int' <IntegralCast>
        `-IntegerLiteral 0xb957ea0 <col:10> 'int' 4
...

The cast to unsigned int for argument 4 is not standard-compliant. Foo is a
function without prototype, so the arguments get default argument promotion,
which implies that the type of the argument should be int rather than unsigned
int.</pre>
        </div>
      </p>
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