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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Need __has_pragma"
href="https://bugs.llvm.org/show_bug.cgi?id=52545">52545</a>
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<th>Summary</th>
<td>Need __has_pragma
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>unspecified
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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>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>scanon@apple.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
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<pre>We have __has_feature and __has_attribute and a number of other variants so
that code can take advantage of new features while still functioning with older
clang versions. We should also have __has_pragma for the same reason.
In particular, I was recently bitten by trying to use the clang fp
reassociate(on) pragma, which is available in clang-11+; rather than producing
an "unknown pragma" warning, older clangs produce the error "invalid option
'reassociate'; expected contract".
An alternative solution (which would have worked in my case) would be to have
unknown pragma options always be a warning instead of an error, but in general
it's a better option to have __has_pragma, because it gives the user the
building block to fallback on a different solution or to produce an error in
cases where that's more appropriate.
I think a minimum-viable __has_pragma would take a string argument that's the
entire pragma body and produce a result of 1 if the string is an accepted
pragma for the current target.</pre>
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