Clang-format 18: Inconsistent ampersand and pointer star spacing with function parameters with nested/interface scope

[vesterij]

clang-format version 18.1.8 and default config

Formatting following code will replicate the issue.

#pragma once

namespace Helper {

    // Correct: CMyClass& myclass
    HRESULT GetSomething(CMyClass& myclass);

    interface MyInterface {
	 // Wrong: CMyClass & myclass
        HRESULT GetSomethingElse(CMyClass& myclass);
    }
}

Clang-format with default config will change formatting a lot but the probem is that when references or pointers to function parameters are first parameters there is an extra space.

You get:
CMyClass & myclass
Instead of:
CMyClass& myclass

But this is only if there is a nested scope (like with MSVC interface) and object is first paramater.

[vesterij]

Compiled version from main and same problem happens with that.

clang-format.exe --version
clang-format version 20.0.0git (https://github.com/llvm/llvm-project.git a466db2b32cccfdbd8bbd27cfa2fb51651192075)

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: Jarno Vesterinen (vesterij)

clang-format version 18.1.8 and default config

Formatting following code will replicate the issue.

#pragma once

namespace Helper
{
	HRESULT GetSomething(
		bool& bOnline,
		long& lMaxCount,
		CMyClass& myclass,
		CPointerToSomething* psomething,
		std::string& szFilter
	);
	
	// Ok.
	HRESULT GetSomethingElse(
		CMyClass& myclass,
		CPointerToSomething* psomething,
		long lId,
		bool& bAvailable,
		CState& state
		CPointerToSomething* psomethingElse,
	);

	// interface
	interface MyInterface
	{
		HRESULT GetSomething(
			bool& bOnline,
			long& lMaxCount,
			CMyClass& myclass,
			CPointerToSomething* psomething,
			std::string& szFilter
		);
		
		// Wrong.
		HRESULT GetSomethingElse(
			CMyClass& myclass,
			CPointerToSomething* psomething,
			long lId,
			bool& bAvailable,
			CState& state
			CPointerToSomething* psomethingElse,
		);
	
	};
	
	// Nested scope
	{
		HRESULT GetSomething(
			bool& bOnline,
			long& lMaxCount,
			CMyClass& myclass,
			CPointerToSomething* psomething,
			std::string& szFilter
		);
		
		// Wrong.
		HRESULT GetSomethingElse(
			CMyClass& myclass,
			CPointerToSomething* psomething,
			long lId,
			bool& bAvailable,
			CState& state
			CPointerToSomething* psomethingElse,
		);
	
	}
}

Clang-format with default config will change formatting a lot but the probem is that when references or pointers to function parameters are first parameters there is an extra space.

You get:
CMyClass & myclass and CPointerToSomething * psomething
Instead of:
CMyClass& myclass and CPointerToSomething* psomething

But this is only if there is a nested scope (like with interface) and object is first paramater.

[llvmbot]

@llvm/issue-subscribers-bug

Author: Jarno Vesterinen (vesterij)

clang-format version 18.1.8 and default config

Formatting following code will replicate the issue.

#pragma once

namespace Helper
{
	HRESULT GetSomething(
		bool& bOnline,
		long& lMaxCount,
		CMyClass& myclass,
		CPointerToSomething* psomething,
		std::string& szFilter
	);
	
	// Ok.
	HRESULT GetSomethingElse(
		CMyClass& myclass,
		CPointerToSomething* psomething,
		long lId,
		bool& bAvailable,
		CState& state
		CPointerToSomething* psomethingElse,
	);

	// interface
	interface MyInterface
	{
		HRESULT GetSomething(
			bool& bOnline,
			long& lMaxCount,
			CMyClass& myclass,
			CPointerToSomething* psomething,
			std::string& szFilter
		);
		
		// Wrong.
		HRESULT GetSomethingElse(
			CMyClass& myclass,
			CPointerToSomething* psomething,
			long lId,
			bool& bAvailable,
			CState& state
			CPointerToSomething* psomethingElse,
		);
	
	};
	
	// Nested scope
	{
		HRESULT GetSomething(
			bool& bOnline,
			long& lMaxCount,
			CMyClass& myclass,
			CPointerToSomething* psomething,
			std::string& szFilter
		);
		
		// Wrong.
		HRESULT GetSomethingElse(
			CMyClass& myclass,
			CPointerToSomething* psomething,
			long lId,
			bool& bAvailable,
			CState& state
			CPointerToSomething* psomethingElse,
		);
	
	}
}

Clang-format with default config will change formatting a lot but the probem is that when references or pointers to function parameters are first parameters there is an extra space.

You get:
CMyClass & myclass and CPointerToSomething * psomething
Instead of:
CMyClass& myclass and CPointerToSomething* psomething

But this is only if there is a nested scope (like with interface) and object is first paramater.

[vesterij]

For some reason function declaration in inner scope is interpreted as an expression IsExpression = true.

This causes ampersand token Type to be set as TT_BinaryOperator instead of TT_PointerOrReference in determineStarAmpUsage:

    // It is very unlikely that we are going to find a pointer or reference type
    // definition on the RHS of an assignment.
    if (IsExpression && !Contexts.back().CaretFound)
      return TT_BinaryOperator;

And token being TT_BinaryOperator causes extra space function parameter list.

Also noticed that in inner scope Line's MustBeDeclaration is false that caused another problem.

This was working differently with Release/16.x

[vesterij]

Changed description to have more simplified example and dropped nested scope without MSVC interface keyword. It was not working with plain nested scope with release/16.x either.

[vesterij]

Found it.

release/18.x clang\lib\Format\UnwrappedLineParser.cpp: 1975

      if (!Style.isCpp() && FormatTok->is(Keywords.kw_interface)) {
        if (parseStructLike())
          return;
        break;
      }

release/16.x clang\lib\Format\UnwrappedLineParser.cpp: 2030

      if (FormatTok->is(Keywords.kw_interface)) {
        if (parseStructLike())
          return;
        break;

So basically handling of nonstandard MSVC keyword interface was fixed in release/18.x

However this keyword is used in our legacy code base, and this change caused all kinds of changes in our formatting.

I can batch this change in our modified version (that has number of other tweaks already). Closing ticket.