[lld] [ELF] Demote symbols in /DISCARD/ discarded sections to Undefined (PR #69295)

[Fangrui Song via llvm-commits]

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@@ -316,12 +316,13 @@ void elf::maybeWarnUnorderableSymbol(const Symbol *sym) {
   if (!config->warnSymbolOrdering)
     return;
 
-  // If UnresolvedPolicy::Ignore is used, no "undefined symbol" error/warning
-  // is emitted. It makes sense to not warn on undefined symbols.
+  // If UnresolvedPolicy::Ignore is used, no "undefined symbol" error/warning is
+  // emitted. It makes sense to not warn on undefined symbols (excluding those
+  // demoted by demoteSymbolsInDiscardedSections).
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MaskRay wrote:

Thanks for the catch. I think both demoteSymbols/demoteLocalSymbolsInDiscardedSections but we probably can just mention demoteSymbols.

https://github.com/llvm/llvm-project/pull/69295