[lld] [LLD][COFF] Fix handling of weak aliases referencing lazy symbols (PR #112243)

[Martin Storsjö via llvm-commits]

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@@ -340,7 +340,10 @@ class Undefined : public Symbol {
   // If this symbol is external weak, try to resolve it to a defined
   // symbol by searching the chain of fallback symbols. Returns the symbol if
   // successful, otherwise returns null.
-  Defined *getWeakAlias();
+  Symbol *getWeakAlias();
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mstorsjo wrote:

In trying to read the diff and the effects of it - I see that a number of callers are switched from `getWeakAlias()` to `getDefinedWeakAlias()` - but what I don't see from the point of view of the diff, is what remaining callers there are, that still are calling `getWeakAlias()`?

Because any caller that is switched to `getDefinedWeakAlias()` will essentially be doing the same as before (minus the UB in `cast<Undefined>()`), but which callers do get the new behaviour of `getWeakAlias()` where it potentially returns something else?

https://github.com/llvm/llvm-project/pull/112243