[clang] [clang-repl] fix vtable symbol duplication error (closes #141039) (PR #185648)

[Emery Conrad via cfe-commits]

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@@ -2097,6 +2097,15 @@ void ItaniumCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
   // Set the correct linkage.
   VTable->setLinkage(Linkage);
 
+  // Track ExternalLinkage vtable definitions so moveLazyEmissionStates() can
+  // tell the next PTU not to re-emit them.  We only do this for ExternalLinkage
+  // because the JIT reliably exports strong symbols cross-module.
+  // WeakODR/LinkOnceODR vtables (e.g. inline key functions, template
+  // instantiations) are not reliably cross-module resolvable in the JIT, so
+  // later PTUs must re-emit their own copy.
+  if (Linkage == llvm::GlobalValue::ExternalLinkage)
+    CGM.markVTableEmitted(RD);
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conrade-ctc wrote:

yup, we can make it abi independent, just pushed the commit. this leaves the ItaniumCXXABI out of it, good catch.

https://github.com/llvm/llvm-project/pull/185648