[clang] [Clang] [NFC] Remove default argument in ASTUnit.h (PR #78566)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (Sirraide)

<details>
<summary>Changes</summary>

This removes a default argument that is currently broken in C++23 mode due to `std::default_delete` now being `constexpr`. This is a known problem (see #<!-- -->74963, #<!-- -->59966, #<!-- -->69996, and a couple more), fixing which will probably take some time, so this at least makes it possible to compile `ASTUnit.h` in C++23 mode.

Note that we can’t simply include the header that provides the definition of the class causing the problem either, as that would create a circular dependency.

---
Full diff: https://github.com/llvm/llvm-project/pull/78566.diff


2 Files Affected:

- (modified) clang/include/clang/Frontend/ASTUnit.h (+1-1) 
- (modified) clang/tools/libclang/CIndexCodeCompletion.cpp (+2-1) 


``````````diff
diff --git a/clang/include/clang/Frontend/ASTUnit.h b/clang/include/clang/Frontend/ASTUnit.h
index fe99b3d5adbfa0..6af712afdcb6d8 100644
--- a/clang/include/clang/Frontend/ASTUnit.h
+++ b/clang/include/clang/Frontend/ASTUnit.h
@@ -902,7 +902,7 @@ class ASTUnit {
                     SourceManager &SourceMgr, FileManager &FileMgr,
                     SmallVectorImpl<StoredDiagnostic> &StoredDiagnostics,
                     SmallVectorImpl<const llvm::MemoryBuffer *> &OwnedBuffers,
-                    std::unique_ptr<SyntaxOnlyAction> Act = nullptr);
+                    std::unique_ptr<SyntaxOnlyAction> Act);
 
   /// Save this translation unit to a file with the given name.
   ///
diff --git a/clang/tools/libclang/CIndexCodeCompletion.cpp b/clang/tools/libclang/CIndexCodeCompletion.cpp
index 196c64e6172274..3c5f390f6d888a 100644
--- a/clang/tools/libclang/CIndexCodeCompletion.cpp
+++ b/clang/tools/libclang/CIndexCodeCompletion.cpp
@@ -765,7 +765,8 @@ clang_codeCompleteAt_Impl(CXTranslationUnit TU, const char *complete_filename,
                     IncludeBriefComments, Capture,
                     CXXIdx->getPCHContainerOperations(), *Results->Diag,
                     Results->LangOpts, *Results->SourceMgr, *Results->FileMgr,
-                    Results->Diagnostics, Results->TemporaryBuffers);
+                    Results->Diagnostics, Results->TemporaryBuffers,
+                    /*SyntaxOnlyAction=*/nullptr);
 
   Results->DiagnosticsWrappers.resize(Results->Diagnostics.size());
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/78566