<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 - clang silently ignores trivial_abi in some cases"
href="https://bugs.llvm.org/show_bug.cgi?id=39683">39683</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>clang silently ignores trivial_abi in some cases
</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>All
</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++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>comexk@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>Target: x86_64-apple-darwin18.2.0
In the following code, the class Test is marked trivial_abi (and is not a
template class), and Clang does not produce any warnings about trivial_abi when
compiling it, yet for the function test() returning a value of that class,
Clang's generated code returns it through memory rather than a register.
I'm not sure whether this class should actually be eligible for trivial_abi or
not, but if not, there definitely should be a warning.
If you change the definition by adding an additional non-template move
constructor, then trivial_abi starts being respected:
+ Test(Test &&other) { x = other.x; }
Tested on latest trunk targeting macOS.
--
struct Test {
int x;
Test(int x) : x(x) {}
template <typename T>
Test(T &&other) { x = other.x; }
Test(const Test &) = delete;
template <typename T>
Test &operator=(T &&other) { x = other.x; }
Test &operator=(const Test &) = delete;
} __attribute__((trivial_abi));
Test test() {
return Test(42);
}</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>