<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 --- - static analyzer not deal with VLA checking well..."
   href="https://llvm.org/bugs/show_bug.cgi?id=27923">27923</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>static analyzer not deal with VLA checking well...
          </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>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>release blocker
          </td>
        </tr>

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

        <tr>
          <th>Component</th>
          <td>Static Analyzer
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>kremenek@apple.com
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>humeafo@gmail.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>clang -cc1  -analyze -analyzer-checker=alpha
llvm/tools/clang/test/Analysis/outofbound-notwork.c 

no expected warnings emmited, after investigation the VLA tracking is not well
dealt with.

void sizeof_vla(int a) {
  if (a == 5) {
    char x[a];
    int y[sizeof(x)];
    y[4] = 4; // no-warning
    y[5] = 5; // expected-warning{{out-of-bound}}
  }
}

to get x's extent, I use 
static SVal getExtentVal(const SubRegion* R, SValBuilder& SB, CheckerContext
&checkerContext) {
  if(auto TR = dyn_cast<const TypedValueRegion>(R)) {
    if (isa<VariableArrayType>(TR->getValueType())) {
      Expr* ext = cast<VariableArrayType>(TR->getValueType())->getSizeExpr();
      ext->dump();
      return checkerContext.getSVal(ext);
    }
  }
  return R->getExtent(SB);
}

to get the symbolic extent of a, but not succeed, am I wrong or it's a defect
of the SA engine?</pre>
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