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

[Ilya Biryukov via cfe-commits]

https://github.com/ilya-biryukov created https://github.com/llvm/llvm-project/pull/79875

Particular example that lead to this is a very long chain of `UsingShadowDecl`s that we hit in our codebase in generated code.

To avoid that, check for stack exhaustion when deserializing the declaration. At that point, we can point to source location of a particular declaration that is being deserialized.

>From d1aaa762ae05defa94289afda163c67731fc607d Mon Sep 17 00:00:00 2001
From: Ilya Biryukov <ibiryukov at google.com>
Date: Mon, 29 Jan 2024 18:55:53 +0100
Subject: [PATCH] [Serialization] Check for stack exhaustion when reading
 declarations

Particular example that lead to this is a very long chain of
`UsingShadowDecl`s that we hit in our codebase in generated code.

To avoid that, check for stack exhaustion when deserializing the
declaration. At that point, we can point to source location of a
particular declaration that is being deserialized.
---
 clang/lib/Serialization/ASTReaderDecl.cpp     |  4 +-
 .../Modules/lots-of-using-shadow-decls.cpp    | 43 +++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/Modules/lots-of-using-shadow-decls.cpp

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 547eb77930b4eec..e2507d7c14a15d0 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -4099,7 +4099,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   // calls to Decl::getASTContext() by Decl's methods will find the
   // TranslationUnitDecl without crashing.
   D->setDeclContext(Context.getTranslationUnitDecl());
-  Reader.Visit(D);
+
+  // Reading some declarations can result in deep recursion.
+  SemaObj->runWithSufficientStackSpace(DeclLoc, [&] { Reader.Visit(D); });
 
   // If this declaration is also a declaration context, get the
   // offsets for its tables of lexical and visible declarations.
diff --git a/clang/test/Modules/lots-of-using-shadow-decls.cpp b/clang/test/Modules/lots-of-using-shadow-decls.cpp
new file mode 100644
index 000000000000000..c3048352842e3f9
--- /dev/null
+++ b/clang/test/Modules/lots-of-using-shadow-decls.cpp
@@ -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)
+
+export struct Base {
+#undef DECLARE
+#define DECLARE(NAME) void func(NAME*);
+TYPES4(Type)
+};
+
+export struct Derived : Base {
+    using Base::func;
+};
+
+//--- use.cpp
+import usings;
+void test() {
+    Derived().func(nullptr); // expected-error{{ambiguous}}
+    // expected-note@* + {{candidate function}}
+}