[clang] [Serialization] Check for stack exhaustion when reading declarations (PR #79875)

[Chuanqi Xu via cfe-commits]

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@@ -0,0 +1,43 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/usings.cppm -o %t/usings.pcm
+// RUN: %clang_cc1 -std=c++20 -fmodule-file=usings=%t/usings.pcm %t/use.cpp -verify -fsyntax-only -Wno-stack-exhausted
+
+// expected-no-diagnostics
+
+//--- usings.cppm
+export module usings;
+
+#define TYPES1(NAME) DECLARE(NAME##a) DECLARE(NAME##b) DECLARE(NAME##c) \
+    DECLARE(NAME##d) DECLARE(NAME##e) DECLARE(NAME##f) DECLARE(NAME##g) \
+    DECLARE(NAME##h) DECLARE(NAME##i) DECLARE(NAME##j) 
+#define TYPES2(NAME) TYPES1(NAME##a) TYPES1(NAME##b) TYPES1(NAME##c) \
+    TYPES1(NAME##d) TYPES1(NAME##e) TYPES1(NAME##f) TYPES1(NAME##g) \
+    TYPES1(NAME##h) TYPES1(NAME##i) TYPES1(NAME##j) 
+#define TYPES3(NAME) TYPES2(NAME##a) TYPES2(NAME##b) TYPES2(NAME##c) \
+    TYPES2(NAME##d) TYPES2(NAME##e) TYPES2(NAME##f) TYPES2(NAME##g) \
+    TYPES2(NAME##h) TYPES2(NAME##i) TYPES2(NAME##j) 
+#define TYPES4(NAME) TYPES3(NAME##a) TYPES3(NAME##b) TYPES3(NAME##c) \
+    TYPES3(NAME##d) TYPES3(NAME##e) TYPES3(NAME##f) TYPES3(NAME##g)
+
+#define DECLARE(NAME) struct NAME {};
+TYPES4(Type)
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ChuanqiXu9 wrote:

> I am not sure if there is an an approach that does not involve structural changes to the AST (i.e. rewriting the ASTReaderDecl somehow, but keeping the AST the same).

To my knowledge, it is only possible by introducing coroutines if we don't want to refactor the current deserializer significantly.

https://github.com/llvm/llvm-project/pull/79875