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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Introduction of -fbracket-depth broke std::array:s longer than 256"
href="https://bugs.llvm.org/show_bug.cgi?id=50178">50178</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Introduction of -fbracket-depth broke std::array:s longer than 256
</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>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>weiss@wsoptics.de
</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>The code at the bottom behaves like this with clang-12:
% clang++ -std=c++17 -c b.cpp
In file included from b.cpp:1:
/usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/include/g++-v10/array:245:52: fatal
error: instantiating fold expression with 257 arguments exceeded expression
nesting limit of 256
-> array<enable_if_t<(is_same_v<_Tp, _Up> && ...), _Tp>,
~~~~~~~~~~~~~~~~~~~~~~~~^~~~
b.cpp:6:12: note: while substituting deduced template arguments into function
template '<deduction guide for array>' [with _Tp = S, _Up = <S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S,
S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S, S>]
std::array a{S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{},
^
1 error generated.
% clang++ -std=c++17 -c -fbracket-depth=512 b.cpp
% echo $?
0
This actually hit our production code and took me a while to reduce. I think
limiting the length of std::array to <= 256 by default is not desirable.
This is the code:
#include<array>
struct S {};
std::array a{S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{}, S{},
S{}};</pre>
</div>
</p>
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