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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - MC-COFF: multiple levels of linkonce_odr aliases produce an unlinkable COFF object"
href="http://llvm.org/bugs/show_bug.cgi?id=17530">17530</a>
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<th>Summary</th>
<td>MC-COFF: multiple levels of linkonce_odr aliases produce an unlinkable COFF object
</td>
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<th>Product</th>
<td>libraries
</td>
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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>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>MC
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>rnk@google.com
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, peter@pcc.me.uk, rafael.espindola@gmail.com, ruiu@google.com
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>$ cat t.ll
@my_alias = alias linkonce_odr void ()* @my_inline
@my_alias2 = alias linkonce_odr void ()* @my_alias
define linkonce_odr void @my_inline() {
ret void
}
define i32 @main() {
call void @my_alias2()
ret i32 0
}
$ llc t.ll -o tll.obj -filetype=obj && link tll.obj -defaultlib:libcmt.lib
-out:t.exe -nologo
tll.obj : error LNK2001: unresolved external symbol _my_alias2
tll.obj : error LNK2001: unresolved external symbol _my_alias
$ dumpbin /symbols tll.obj
COFF SYMBOL TABLE
000 00000000 SECT1 notype Static | .text
Section length 8, #relocs 1, #linenums 0, checksum 0
002 00000000 SECT2 notype Static | .text$my_inline
Section length 1, #relocs 0, #linenums 0, checksum 0,
selection 2 (pick any)
004 00000001 ABS notype Static | @feat.00
005 00000000 SECT2 notype () External | _my_inline
006 00000000 SECT1 notype () External | _main
007 00000000 UNDEF notype WeakExternal | _my_alias2
Default index 9 library search
009 00000000 UNDEF notype WeakExternal | _my_alias
Default index 5 library search
The symbol at index 7 points to index 9 which points to index 5.
Rui says that these weak external aliases are more like fallbacks. The symbol
is still undefined, and if nobody provides a definition, then it is resolved to
the "default index". So, it looks like you can't do this twice. You can't
fallback to a fallback symbol.
I'm filing this as an MC bug, since any IR could hit this, but I'll probably
try to patch clang to avoid this.</pre>
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