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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 emitting RIP-relative relocation for weak external on Windows x86-64"
href="https://bugs.llvm.org/show_bug.cgi?id=37598">37598</a>
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<th>Summary</th>
<td>clang emitting RIP-relative relocation for weak external on Windows x86-64
</td>
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<th>Product</th>
<td>libraries
</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
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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
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>smeenai@fb.com
</td>
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<th>CC</th>
<td>compnerd@compnerd.org, llvm-bugs@lists.llvm.org, rnk@google.com
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<p>
<div>
<pre>% cat reduced.ll
@Weak = extern_weak global i32
define i32* @getWeak() {
ret i32* @Weak
}
% clang -target x86_64-windows-msvc -S -o - reduced.ll
.text
.def getWeak;
.scl 2;
.type 32;
.endef
.globl getWeak # -- Begin function getWeak
.p2align 4, 0x90
getWeak: # @getWeak
# %bb.0:
leaq Weak(%rip), %rax
retq
# -- End function
.weak Weak
The issue is that LLVM implements weak symbols for COFF through the weak
external mechanism, and it emits an absolute symbol with the value of 0 to
serve as the fallback symbol. We'll therefore end up with a RIP-relative
relocation against an absolute symbol in the case where Weak isn't defined.
link errors out for this:
error LNK2016: absolute symbol 'Weak' used as target of REL32 relocation in
section 1
LLD accepts it silently; I'll file a separate bug for that.</pre>
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