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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 - LLD ICF needs to consider exception tables in .xdata as part of .text equivalence"
href="https://bugs.llvm.org/show_bug.cgi?id=35337">35337</a>
</td>
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<th>Summary</th>
<td>LLD ICF needs to consider exception tables in .xdata as part of .text equivalence
</td>
</tr>
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<th>Product</th>
<td>lld
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>COFF
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>LLD mislinks this program because the .text contents of these two functions are
the same, but the .xdata exception handler table is different:
extern "C" void __ImageBase() noexcept(false);
void __declspec(dllexport) foo() {
try {
__ImageBase();
} catch (int) {
}
}
void __declspec(dllexport) baz() {
try {
__ImageBase();
} catch (double) {
}
}
Compile and link like so, and observe that the export RVAs are the same:
$ clang-cl -EHsc -O1 -MD t.cpp -c && lld-link t.obj -dll -noentry -opt:icf
-force
C:\src\llvm-project\build\bin\lld-link.exe: warning: t.obj: undefined symbol:
__CxxFrameHandler3
C:\src\llvm-project\build\bin\lld-link.exe: warning:
msvcrt.lib(delete_scalar.obj): undefined symbol: free
$ llvm-readobj -coff-exports t.dll
File: t.dll
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit
Export {
Ordinal: 0
Name:
RVA: 0x0
}
Export {
Ordinal: 1
Name: ?baz@@YAXXZ
RVA: 0x6000
}
Export {
Ordinal: 2
Name: ?foo@@YAXXZ
RVA: 0x6000
}
If this were a full working program, bar would not be able to catch exceptions
of type double thrown from __ImageBase and would incorrectly catch 'int'
exceptions.</pre>
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