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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 - Fragment variable size verification fails during LTO in presence of ODR violations"
href="https://bugs.llvm.org/show_bug.cgi?id=38608">38608</a>
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<th>Summary</th>
<td>Fragment variable size verification fails during LTO in presence of ODR violations
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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
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<th>Status</th>
<td>NEW
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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>DebugInfo
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>rnk@google.com
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<th>CC</th>
<td>bjorn.a.pettersson@ericsson.com, llvm-bugs@lists.llvm.org, llvm@inglorion.net, peter@pcc.me.uk
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<pre>Our Chromium ThinLTO bot has been red longer than we have history for it, and I
think it was caused by r334830 from June.
During LTO, our bot is now producing this error:
fragment is larger than or outside of variable
call void @llvm.dbg.value(metadata i8 %9, metadata !2265359, metadata
!DIExpression(DW_OP_LLVM_fragment, 96, 8)), !dbg !2265363
!2265359 = !DILocalVariable(name: "p", scope: !2265356, f
Here is a reduction of the problem:
// a.cpp
struct ViolateODR {
int x;
};
int use_small_struct(ViolateODR o) {
return o.x;
}
int do_sroa(int x, int y);
int main() {
ViolateODR o = {0};
return use_small_struct(o) + do_sroa(1, 2);
}
// b.cpp
struct ViolateODR {
int x;
};
int use_small_struct(ViolateODR o) {
return o.x;
}
int do_sroa(int x, int y);
int main() {
ViolateODR o = {0};
return use_small_struct(o) + do_sroa(1, 2);
}
// script
$ clang-cl -Z7 -flto=thin -c a.cpp b.cpp -O2 && lld-link a.obj b.obj -out:t.exe
fragment covers entire variable
call void @llvm.dbg.value(metadata i32 %3, metadata !17, metadata
!DIExpression(DW_OP_LLVM_fragment, 0, 32)), !dbg !24
!17 = !DILocalVariable(name: "o", scope: !10, file: !1, line: 6, type: !18)
OK, so maybe I got a.cpp and b.cpp swapped, but you see the point. I don't
think verifier errors during LTO are a reasonable failure mode for ODR
violations.
I would prefer it if instead dbg.value problems could be reported as warnings
and we could locally discard the problematic dbg.value instructions.</pre>
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