[clang] [C++20][Modules] Fix crash when function and lambda inside loaded from different modules (PR #109167)

[Reid Kleckner via cfe-commits]

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@@ -5706,6 +5707,27 @@ void ASTWriter::WriteDeclAndTypes(ASTContext &Context) {
     Stream.EmitRecord(DELAYED_NAMESPACE_LEXICAL_VISIBLE_RECORD,
                       DelayedNamespaceRecord);
 
+  if (!FunctionToLambdasMap.empty()) {
+    // TODO: on disk hash table for function to lambda mapping might be more
+    // efficent becuase it allows lazy deserialization.
+    RecordData FunctionToLambdasMapRecord;
+    for (const auto &Pair : FunctionToLambdasMap) {
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rnk wrote:

This looks like the non-deterministic for loop, this is the DenseMap iteration that decides what to write to disk. I'll just send a patch to make this a MapVector.

https://github.com/llvm/llvm-project/pull/109167