[clang] [Clang][Sema] fix outline member function template with default align crash (PR #78400)

[Qizhi Hu via cfe-commits]

https://github.com/jcsxky updated https://github.com/llvm/llvm-project/pull/78400

>From b9de8c52a2ffbd03c8a5368f6e62ba6c68ce2125 Mon Sep 17 00:00:00 2001
From: huqizhi <huqizhi at feysh.com>
Date: Wed, 17 Jan 2024 14:16:34 +0800
Subject: [PATCH] [Clang][Sema] fix outline member function template with
 default align crash

---
 clang/docs/ReleaseNotes.rst                   |  3 ++
 clang/lib/Sema/SemaTemplateInstantiate.cpp    | 13 ++++-
 clang/test/SemaTemplate/default-parm-init.cpp | 50 +++++++++++++++++++
 3 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/SemaTemplate/default-parm-init.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8bb26fcae18d6b..ccdce2c299b022 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -828,6 +828,9 @@ Bug Fixes in This Version
 - Fix an issue with missing symbol definitions when the first coroutine
   statement appears in a discarded ``if constexpr`` branch.
   Fixes (`#78290 <https://github.com/llvm/llvm-project/issues/78290>`_)
+- Fix crash when specialize out-of-line member function with default parameter
+  and issue with incorrect specialization of the initialization of default parameter.
+  Fixes (`#68490 <https://github.com/llvm/llvm-project/issues/68490>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index fc80515b45e35b..d310dfdd61c600 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -3051,6 +3051,7 @@ bool Sema::SubstDefaultArgument(
     //   default argument expression appears.
     ContextRAII SavedContext(*this, FD);
     std::unique_ptr<LocalInstantiationScope> LIS;
+    MultiLevelTemplateArgumentList NewTemplateArgs = TemplateArgs;
 
     if (ForCallExpr) {
       // When instantiating a default argument due to use in a call expression,
@@ -3063,11 +3064,19 @@ bool Sema::SubstDefaultArgument(
           /*ForDefinition*/ false);
       if (addInstantiatedParametersToScope(FD, PatternFD, *LIS, TemplateArgs))
         return true;
+      if (FD->isOutOfLine()) {
+        TemplateArgumentList *CurrentTemplateArgumentList =
+            TemplateArgumentList::CreateCopy(getASTContext(),
+                                             TemplateArgs.getInnermost());
+        NewTemplateArgs = getTemplateInstantiationArgs(
+            FD, FD->getDeclContext(), /*Final=*/false,
+            CurrentTemplateArgumentList, /*RelativeToPrimary=*/true);
+      }
     }
 
     runWithSufficientStackSpace(Loc, [&] {
-      Result = SubstInitializer(PatternExpr, TemplateArgs,
-                                /*DirectInit*/false);
+      Result = SubstInitializer(PatternExpr, NewTemplateArgs,
+                                /*DirectInit*/ false);
     });
   }
   if (Result.isInvalid())
diff --git a/clang/test/SemaTemplate/default-parm-init.cpp b/clang/test/SemaTemplate/default-parm-init.cpp
new file mode 100644
index 00000000000000..4bcea7eaa10176
--- /dev/null
+++ b/clang/test/SemaTemplate/default-parm-init.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
+// expected-no-diagnostics
+
+template<typename TemplateParam>
+struct Problem{
+  template<typename FunctionTemplateParam>
+  constexpr int FuncAlign(int param = alignof(FunctionTemplateParam));
+
+  template<typename FunctionTemplateParam>
+  constexpr int FuncSizeof(int param = sizeof(FunctionTemplateParam));
+
+  template<typename FunctionTemplateParam>
+  constexpr int FuncAlign2(int param = alignof(TemplateParam));
+
+  template<typename FunctionTemplateParam>
+  constexpr int FuncSizeof2(int param = sizeof(TemplateParam));
+};
+
+template <>
+template<typename FunctionTemplateParam>
+constexpr int Problem<int>::FuncAlign(int param) {
+	return param;
+}
+
+template <>
+template<typename FunctionTemplateParam>
+constexpr int Problem<int>::FuncSizeof(int param) {
+	return param;
+}
+
+template <>
+template<typename FunctionTemplateParam>
+constexpr int Problem<int>::FuncAlign2(int param) {
+	return param;
+}
+
+template <>
+template<typename FunctionTemplateParam>
+constexpr int Problem<int>::FuncSizeof2(int param) {
+	return param;
+}
+
+int main(){
+    Problem<int> p = {};
+    static_assert(p.FuncAlign<char>() == alignof(char));
+    static_assert(p.FuncSizeof<char>() == sizeof(char));
+    static_assert(p.FuncAlign2<char>() == alignof(int));
+    static_assert(p.FuncSizeof2<char>() == sizeof(int));
+}