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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [MS] Devirtualizing a method call on the result of a static_cast uses wrong this adjustment"
href="https://llvm.org/bugs/show_bug.cgi?id=27621">27621</a>
</td>
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<tr>
<th>Summary</th>
<td>[MS] Devirtualizing a method call on the result of a static_cast uses wrong this adjustment
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Blocks</th>
<td>12477
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider:
struct A { virtual void f(); };
struct B { virtual void g(); };
struct C final : A, B {
virtual void h();
void g() override;
};
void doit(C *p) {
// Fails to adjust from C* to B* when calling C::g
static_cast<B*>(p)->g();
}
The problem is that we pass the wrong CXXMethodDecl to
adjustThisArgumentForVirtualFunctionCall. We pass B::g instead of C::g. B::g
has no 'this' adjustment in its prologue.
The fix is trivial:
diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index a90610f..c6f46c3 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/lib/CodeGen/CGExprCXX.cpp
@@ -274,7 +274,7 @@ RValue
CodeGenFunction::EmitCXXMemberOrOperatorMemberCallExpr(
if (MD->isVirtual()) {
This = CGM.getCXXABI().adjustThisArgumentForVirtualFunctionCall(
- *this, MD, This, UseVirtualCall);
+ *this, CalleeDecl, This, UseVirtualCall);
}
return EmitCXXMemberOrOperatorCall(MD, Callee, ReturnValue,
This.getPointer(),</pre>
</div>
</p>
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