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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Modifying data member when passing temporary to function accepting T const & not considered constexpr"
href="https://bugs.llvm.org/show_bug.cgi?id=32860">32860</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Modifying data member when passing temporary to function accepting T const & not considered constexpr
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>4.0
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++14
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david@doublewise.net
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>struct S {
constexpr S() {
x = true;
}
bool x = false;
};
constexpr bool f(S const &) {
return true;
}
// Test passes if you define FIX
#ifdef FIX
constexpr bool f(S &&) {
return true;
}
#endif
int main() {
// All of these work
constexpr auto lvalue = S{};
constexpr auto rvalue_member = S{}.x;
constexpr auto lvalue_member = lvalue.x;
constexpr auto lvalue_function_call = f(lvalue);
// This fails
constexpr auto rvalue_function_call = f(S{});
}
<span class="quote">> clang++ source/main.cpp -std=c++14</span >
source/main.cpp:28:17: error: constexpr variable 'rvalue_function_call' must be
initialized by a constant expression
constexpr auto rvalue_function_call = f(S{});
^ ~~~~~~
source/main.cpp:3:5: note: modification of object of const-qualified type
'const bool' is not allowed in a constant expression
x = true;
^
source/main.cpp:28:42: note: in call to 'S()'
constexpr auto rvalue_function_call = f(S{});
^
1 error generated.
This same error happens with -std=c++1z. This code was accepted in clang 3.9</pre>
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