[clang] [clang][CrossTU] Indicate weak link attribute in ExternalDefMap. (PR #204188)

[Balázs Benics via cfe-commits]

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@@ -279,6 +306,8 @@ CrossTranslationUnitContext::~CrossTranslationUnitContext() {}
 std::optional<std::string>
 CrossTranslationUnitContext::getLookupName(const Decl *D) {
   SmallString<128> DeclUSR;
+  if (D->hasAttr<WeakAttr>())
+    DeclUSR.push_back('-');
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steakhal wrote:

This is a fair point. However, I don't think a broader scope should deter us from doing the right thing.
We should seek consensus on the llvm forums to gain feedback form clang area and clangd maintainers in particular about how to handle weak symbols and how should (if at all) be represented in USRs.
Should I post something on the forums or you will do it?

https://github.com/llvm/llvm-project/pull/204188