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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang 12 applies -fbracket-depth to fold expressions, which breaks Boost.Mp11"
href="https://bugs.llvm.org/show_bug.cgi?id=49629">49629</a>
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<th>Summary</th>
<td>Clang 12 applies -fbracket-depth to fold expressions, which breaks Boost.Mp11
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Frontend
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>pdimov@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Boost.Mp11 uses fold expressions internally in the implementation of some of
its algorithms, such as mp_all_of. These algorithms are legitimately applied by
users to lists of (e.g.) 1089 elements (this is easy to achieve when automating
tests with mp_product - 1089 is 33*33, for instance.)
This has worked fine on all Clangs so far, but it breaks under the new 12,
because now -fbracket-depth seems to apply to fold expressions, and its default
value of 256 may be fine for hand-written code, but it's way too low for fold
expressions.
Ref. <a href="https://travis-ci.org/github/boostorg/mp11/jobs/762566614#L1087">https://travis-ci.org/github/boostorg/mp11/jobs/762566614#L1087</a></pre>
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