[PATCH] D130208: [lld-macho] Fix assertion when two symbols at same addr have unwind info

[Alex Brachet via Phabricator via llvm-commits]

abrachet added inline comments.


================
Comment at: lld/MachO/InputFiles.cpp:1536
+      // infrequently (only when handling the output of `ld -r`).
+      funcSym = findSymbolAtOffset(cast<ConcatInputSection>(funcSym->isec),
+                                   funcSym->value);
----------------
int3 wrote:
> int3 wrote:
> > thakis wrote:
> > > We hit this assert in "normal" builds: https://bugs.chromium.org/p/chromium/issues/detail?id=1346125#c1
> > > 
> > > Do you want a repro file for that?
> > > 
> > > Anyways, addressing the assert quickly would be good :) (either revert if hitting this on a normal build is surprising and needs more investigation, or by landing this fix here)
> > Just to confirm, are you sure the "normal" build doesn't pull in any 3rd-party lib that could've been passed through `ld -r`?
> > 
> > I wasn't able to generate it the problem via llvm-mc in my testing, but I could certainly have missed something. Repro file wouldn't really help to figure out the compiler flags that trigger it though...
> > 
> > It doesn't look like the assert triggers at all on `chromium_framework` at least, so I think it's safe to say that it's a fairly uncommon code path
> > It doesn't look like the assert triggers at all on chromium_framework at least, so I think it's safe to say that it's a fairly uncommon code path
> 
> More precisely, an `assert(false)` in this `if` branch doesn't get tripped while linking chromium_framework.
> 
> Landing this now, we can tweak the comment as needed later
Hi this is crashing for us too I've uploaded a reproducer here https://drive.google.com/file/d/1tz3feLMfR-2N8SMxT5dqLqAN3dUVSGRQ/view?usp=sharing. Though it seems like not all input files correctly made it into the reproducer.
See https://ci.chromium.org/ui/p/fuchsia/builders/prod/clang-mac-xarm64/b8807891867843444577/overview which is an lto build of llvm. If it's helpful here's what `funcSym` looks like before the crash
```
(lldb) p *funcSym
(lld::macho::Defined) $9 = {
  lld::macho::Symbol = {
    gotIndex = 4294967295
    lazyBindOffset = 4294967295
    stubsHelperIndex = 4294967295
    stubsIndex = 4294967295
    symtabIndex = 4294967295
    symbolKind = DefinedKind
    nameData = 0x000000011986014f "__ZNSt3__212basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEC1B6v15000IDnEEPKc"
    file = 0x000000011a849a00
    nameSize = 82
    isUsedInRegularObj = true
    used = false
  }
  overridesWeakDef = false
  privateExtern = true
  includeInSymtab = true
  wasIdenticalCodeFolded = false
  thumb = false
  referencedDynamically = false
  noDeadStrip = false
  interposable = false
  weakDefCanBeHidden = false
  weakDef = true
  external = true
  isec = nullptr
  value = 0
  size = 0
  unwindEntry = nullptr
}
```


Repository:
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https://reviews.llvm.org/D130208