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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - -fmodules-local-submodule-visibility fails to merge weak variable definitions."
href="https://llvm.org/bugs/show_bug.cgi?id=31246">31246</a>
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<th>Summary</th>
<td>-fmodules-local-submodule-visibility fails to merge weak variable definitions.
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Modules
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>eric@efcs.ca
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=17706" name="attach_17706" title="full reproducer">attachment 17706</a> <a href="attachment.cgi?id=17706&action=edit" title="full reproducer">[details]</a></span>
full reproducer
I'm not exactly sure if this is a bug, because weak variable definitions aren't
standard C++; However llvm/Config/abi-breaking.h uses the feature and this
causes the standalone Clang modules build to fail due to multiple definitions
of `VerifyEnableABIBreakingChecks`.
I've attached a full reproducer and Makefile which triggers the bug.
I'm not sure how Clang should merge weak variable definitions, or if it's even
possible.
Basic reproducer:
// foo.h
__attribute__((weak) int x = 42;
// module1.h
#include "foo.h"
// module2.h
#include "foo.h"
// module.modulemap
module test_modules {
module module1 {
header "module1.h"
export *
}
module module2 {
header "module2.h"
export *
}
}
// test.cpp
#include "module1.h"</pre>
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