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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 - Crash when expanding an empty fold expression"
href="https://bugs.llvm.org/show_bug.cgi?id=41845">41845</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Crash when expanding an empty fold expression
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Macintosh
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</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>ryan.brown@ableton.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>Created <span class=""><a href="attachment.cgi?id=21932" name="attach_21932" title="Crash Log">attachment 21932</a> <a href="attachment.cgi?id=21932&action=edit" title="Crash Log">[details]</a></span>
Crash Log
See <a href="https://godbolt.org/z/QJQ4A7">https://godbolt.org/z/QJQ4A7</a>.
#include <tuple>
#include <type_traits>
#include <utility>
template <typename... DstArgs>
struct ArgsPackChecker
{
template <typename... SrcArgs>
using EnableIf = std::enable_if_t<
(std::is_convertible_v<SrcArgs, DstArgs> && ...)>;
};
template <typename DstArgsTuple,
typename IndexSeq =
std::make_index_sequence<std::tuple_size_v<DstArgsTuple>>>
struct ArgsChecker;
template <typename DstArgsTuple, int... Is>
struct ArgsChecker<DstArgsTuple, std::index_sequence<Is...>>
{
template <typename... SrcArgs>
using EnableIf =
typename ArgsPackChecker<std::tuple_element_t<Is,
DstArgsTuple>...>::template EnableIf<SrcArgs...>;
};
template <typename... Args,
typename = typename ArgsChecker<std::tuple<>>::template
EnableIf<Args...>>
void f(Args&&... args)
{
}
This builds without an error with GCC 9.1, but crashes with clang trunk. The
attached crash backtrace was generated using Xcode 10.2.1 using the following
command:
$ clang -std=c++17 test.cpp
clang: error: unable to execute command: Segmentation fault: 11
clang: error: clang frontend command failed due to signal (use -v to see
invocation)
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.5.0
Thread model: posix
InstalledDir:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
clang: note: diagnostic msg: PLEASE submit a bug report to
<a href="http://developer.apple.com/bugreporter/">http://developer.apple.com/bugreporter/</a> and include the crash backtrace,
preprocessed source, and associated run script.
clang: note: diagnostic msg:
********************
PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg:
/var/folders/v1/0ffrrhw11394l1p_rl193z340000gn/T/test-87fcfd.cpp
clang: note: diagnostic msg:
/var/folders/v1/0ffrrhw11394l1p_rl193z340000gn/T/test-87fcfd.sh
clang: note: diagnostic msg: Crash backtrace is located in
clang: note: diagnostic msg:
/Users/ryan/Library/Logs/DiagnosticReports/clang_<YYYY-MM-DD-HHMMSS>_<hostname>.crash
clang: note: diagnostic msg: (choose the .crash file that corresponds to your
crash)
clang: note: diagnostic msg:
********************</pre>
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