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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang emits __attribute__((__used__)) functions in submodules that weren't imported"
href="https://bugs.llvm.org/show_bug.cgi?id=48501">48501</a>
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<th>Summary</th>
<td>Clang emits __attribute__((__used__)) functions in submodules that weren't imported
</td>
</tr>
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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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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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>
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<th>Reporter</th>
<td>teemperor@gmail.com
</td>
</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>The example below reproduces the bug. 'use.h' is never actually imported by
main.cpp, but as it's in the same top-level module as 'other.h', the
'call_undefined' function is still deserialised and emitted. Note that this
happens with local-submodule-visibility turned on and off (at least with LSV=on
this seems like a bug):
$ cat main.cpp
#include "other.h"
int main() {}
$ cat other.h
struct Foo {
};
$ cat use.h
int undefined();
__attribute__((__used__))
inline int call_undefined() { undefined(); }
$ cat module.modulemap
module A {
module Use { header "use.h" export * }
module Other { header "other.h" export * }
}
$ clang main.cpp -fmodules -fcxx-modules -Rmodule-build
-fmodules-cache-path=pcms -Xclang -fmodules-local-submodule-visibility
Undefined symbols for architecture x86_64:
"undefined()", referenced from:
call_undefined() in main-fe42f9.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ clang main.cpp -fmodules -fcxx-modules -Rmodule-build
-fmodules-cache-path=pcms -Xclang -fmodules-local-submodule-visibility -S
-emit-llvm -o - | grep undefined
@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()*
@_Z14call_undefinedv to i8*)], section "llvm.metadata"
define linkonce_odr i32 @_Z14call_undefinedv() #0 {
%2 = call i32 @_Z9undefinedv()
declare i32 @_Z9undefinedv() #1</pre>
</div>
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