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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - `-fmodules-local-submodule-visibility` does not work correctly with Objective-C"
href="https://bugs.llvm.org/show_bug.cgi?id=46248">46248</a>
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<th>Summary</th>
<td>`-fmodules-local-submodule-visibility` does not work correctly with Objective-C
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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</tr>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>mboehme@google.com
</td>
</tr>
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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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<pre>Multiple places in AST/DeclObjC.{h,cpp} and Sema/SemaDeclObjC.cpp use
Decl::isHidden() instead of Sema::isVisible().
These two methods are equivalent only if -fmodules-local-submodule-visibility
is not turned on.
If -fmodules-local-submodule-visibility is turned on, Decl::isHidden() can
return true for declarations that have been made visible by importing the
(sub)module that owns them. (See also the FIXME in the comment for
Decl::isHidden().) As a result, the Objective-C code using Decl::isHidden()
will falsely assume that such declarations are hidden when in fact they are
visible.
For examples of how this causes wrong behavior, witness how adding the
-fmodules-local-submodule-visibility option to tests objc-categories.m,
objc-category-2.m and objc-category-3.m in test/Modules causes these tests to
fail.
Fixing this in Sema/SemaDeclObjC.cpp is easy, as Decl::isHidden() can simply be
replaced by Sema::isVisible().
Fixing this in AST/DeclObjC.{h,cpp} is more difficult as AST is not allowed to
depend on Sema. As a result, the functions in question and all of their callers
need to be moved to Sema. From what I have seen, this is a non-trivial
undertaking.
For more context, see also description on this change:
<a href="https://github.com/llvm/llvm-project/commit/90dc5254725e32c0fab65213c554b689a2a0bbbf">https://github.com/llvm/llvm-project/commit/90dc5254725e32c0fab65213c554b689a2a0bbbf</a>
Also note this in-review change, which changes the name of Decl::isHidden() to
more accurately reflect what it does:
<a href="https://reviews.llvm.org/D81392">https://reviews.llvm.org/D81392</a></pre>
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