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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - `__has_feature(cxx_exceptions)` has different value in automatic crash reproducer than in original input code, making it unusable with eg absl code"
href="https://bugs.llvm.org/show_bug.cgi?id=52007">52007</a>
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<th>Summary</th>
<td>`__has_feature(cxx_exceptions)` has different value in automatic crash reproducer than in original input code, making it unusable with eg absl code
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Driver
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>nicolasweber@gmx.de
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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>$ cat feat.cc
#if __has_feature(cxx_exceptions)
int a = 1;
#else
int a = 0;
#endif
#pragma clang __debug crash
When preprocessing, this prints:
$ out/gn/bin/clang-cl -c feat.cc -fcrash-diagnostics-dir=. /E
# 1 "feat.cc"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 369 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "feat.cc" 2
int a = 0;PLEASE submit a bug report
So it takes the else branch. But the crash file written by the driver looks
like:
$ cat feat-c41bad.cpp
# 1 "<built-in>"
# 1 "feat.cc"
#if 0 /* disabled by -frewrite-includes */
#if __has_feature(cxx_exceptions)
#endif
#endif /* disabled by -frewrite-includes */
#if 1 /* evaluated by -frewrite-includes */
# 2 "feat.cc"
int a = 1;
#else
# 4 "feat.cc"
int a = 0;
#endif
# 6 "feat.cc"
#pragma clang __debug crash
So that takes the `#if` branch.
That's kind of bad!
And it's a problem in practice because absl tries to use `try` if `
__has_feature(cxx_exceptions)`, so the crash reproducer generated for code
containing absl then fails to compile and can't reproduce anything.</pre>
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