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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 --- - Clang crash on invalid with sizeof undeduced auto type"
href="https://llvm.org/bugs/show_bug.cgi?id=28116">28116</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Clang crash on invalid with sizeof undeduced auto type
</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>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>rtrieu@google.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>$ cat test.cpp
struct S {
template <typename T> struct M;
template <typename T>
typename M<T>::D operator-(const T& other) const { }
template <typename T>
struct M {
static_assert(sizeof(T) == -1, "");
};
};
struct I {
const S& Get() const;
};
template<typename T1>
T1 F(T1 v1, T1 v2);
void Foo(const I& i) {
auto R = i.Get();
auto w_W = F(R, R_W);
auto Z = 0.5 * (R - R_W);
}
$ clang test.cpp -std=c++11
test.cpp:22:19: error: use of undeclared identifier 'R_W'
auto w_W = F(R, R_W);
^
clang: ../tools/clang/lib/AST/ASTContext.cpp:1773: clang::TypeInfo
clang::ASTContext::getTypeInfoImpl(const clang::Type *) const: Assertion
`!A->getDeducedType().isNull() && "cannot request the size of an undeduced or
dependent auto type"' failed.
It looks like S::M<T> gets instantiated with T being an undeduced auto type.
The static_assert then attempts to evaluate sizeof(T), causing the crash.</pre>
</div>
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