<html>
<head>
<base href="https://bugs.llvm.org/">
</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 - "lambda expression in default argument cannot capture any entity" is not correct"
href="https://bugs.llvm.org/show_bug.cgi?id=45032">45032</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>"lambda expression in default argument cannot capture any entity" is not correct
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>arthur.j.odwyer@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>// <a href="https://godbolt.org/z/mWxfE2">https://godbolt.org/z/mWxfE2</a>
void g6(int = ([x=1]{ return x; })());
test.cc:2:16: error: lambda expression in default argument cannot capture any
entity
void g6(int = ([x=1]{ return x; })());
^
The declaration of "g6" is taken directly from the example code in
<a href="https://eel.is/c++draft/expr.prim.lambda#capture-9">https://eel.is/c++draft/expr.prim.lambda#capture-9</a>
The text says:
<span class="quote">> Because local entities are not odr-usable within a default argument, a lambda-expression appearing in a default argument cannot implicitly or explicitly capture any local entity. Such a lambda-expression can still have an init-capture if any full-expression in its initializer satisfies the constraints of an expression appearing in a default argument.</span >
Notice: any _local_ entity. GCC, MSVC, and ICC seem to implement the "any local
entity" wording correctly; only Clang rejects code like "g6".
The full test case from the Standard is:
void f2() {
int i = 1;
void g1(int = ([i]{ return i; })()); // error
void g2(int = ([i]{ return 0; })()); // error
void g3(int = ([=]{ return i; })()); // error
void g4(int = ([=]{ return 0; })()); // OK
void g5(int = ([]{ return sizeof i; })()); // OK
void g6(int = ([x=1]{ return x; })()); // OK (but Clang rejects it)
void g7(int = ([x=i]{ return x; })()); // error
}</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>