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

[Ilya Biryukov 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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ilya-biryukov wrote:

The test is purely for illustrative purposes, it actually takes too long to run, so I think we should not put it here.
This produces 7k declarations, it was enough to have a stack exhaustion in a release build on my local machine.

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