generate libclang's llgo binding with empty.

[luoliwoshang]

{
	"name": "clang",
	"cflags": "-I/opt/homebrew/Cellar/llvm@19/19.1.7/include  -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS",
	"libs": "-L/opt/homebrew/Cellar/llvm@19/19.1.7/lib -lclang",
	"include": [
		"clang-c/Index.h",
		"clang-c/BuildSystem.h",
		"clang-c/CXDiagnostic.h",
		"clang-c/CXErrorCode.h",
		"clang-c/CXFile.h",
		"clang-c/CXSourceLocation.h",
		"clang-c/CXString.h",
		"clang-c/ExternC.h",
		"clang-c/Platform.h",
	],
	"cplusplus": true,
	"headerOnly": true
}

the index.go only have follow macro define

package clang

import _ "unsafe"

const CINDEX_VERSION_MAJOR = 0
const CINDEX_VERSION_MINOR = 64

[luoliwoshang]

@xgopilot invest it!

[fennoai]

Investigation Complete: Root Cause Identified ✓

Issue: Libclang bindings generate empty output (only macros)

---

Root Cause

The problem is "cplusplus": true in your configuration. The libclang C API headers (clang-c/Index.h and related files) are C headers, not C++ headers. They use extern "C" linkage and C function declarations.

When cplusplus: true is set, llcppg's parser (_xtool/llcppsymg/internal/symg/parse.go:253-260) looks for:

• CursorCXXMethod (C++ methods)
• CursorConstructor (C++ constructors)
• CursorDestructor (C++ destructors)
• CursorFunctionDecl with specific C++ attributes

However, clang-c headers only contain C function declarations (CursorFunctionDecl with C linkage), which are filtered out when cplusplus: true.

---

Solution

Change "cplusplus": true to "cplusplus": false in your configuration:

{
	"name": "clang",
	"cflags": "-I/opt/homebrew/Cellar/llvm@19/19.1.7/include -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS",
	"libs": "-L/opt/homebrew/Cellar/llvm@19/19.1.7/lib -lclang",
	"include": [
		"clang-c/Index.h",
		"clang-c/BuildSystem.h",
		"clang-c/CXDiagnostic.h",
		"clang-c/CXErrorCode.h",
		"clang-c/CXFile.h",
		"clang-c/CXSourceLocation.h",
		"clang-c/CXString.h",
		"clang-c/ExternC.h",
		"clang-c/Platform.h"
	],
	"cplusplus": false,
	"headerOnly": true
}

---

Why This Happens

From _xtool/llcppsymg/internal/symg/parse.go:248-267:

func (p *SymbolProcessor) visitTop(cursor, parent clang.Cursor) clang.ChildVisitResult {
	filename := cursorFileName(cursor)
	switch cursor.Kind {
	case clang.CursorNamespace, clang.CursorClassDecl:
		clangutils.VisitChildren(cursor, p.visitTop)
	case clang.CursorCXXMethod, clang.CursorFunctionDecl, clang.CursorConstructor, clang.CursorDestructor:
		isPublicFunc := cursor.Kind == clang.CursorFunctionDecl &&
			cursor.StorageClass() != clang.SCStatic
		
		isPublicMethod := cursor.CXXAccessSpecifier() == clang.CXXPublic &&
			cursor.Kind == clang.CursorCXXMethod ||
			cursor.Kind == clang.CursorConstructor ||
			cursor.Kind == clang.CursorDestructor
		
		if p.isSelfFile(filename) && (isPublicFunc || isPublicMethod) {
			p.collectFuncInfo(cursor)
		}
	}
	return clang.ChildVisit_Continue
}

When parsing C headers:

• Functions like clang_createIndex() have cursor.Kind == CursorFunctionDecl
• They should match isPublicFunc condition
• But the parsing behavior differs based on whether the translation unit is created with C or C++ mode

The isCpp flag is passed to clangutils.CreateTranslationUnit() in parse.go:301-308, which affects how libclang parses the headers.

---

Additional Notes

1. Header Order: Your include order looks correct, with dependencies listed first
2. Macros Work: Macros are processed separately by the preprocessor, which is why CINDEX_VERSION_MAJOR and CINDEX_VERSION_MINOR appear in the output
3. Functions Missing: The 400+ C functions in clang-c/Index.h (like clang_createIndex, clang_getFile, clang_getCursor, etc.) will only be detected with "cplusplus": false

---

Branch: xgopilot/claude/issue-565-1760669992

[fennoai]

@luoliwoshang The issue has been identified! Please check the investigation above.

TL;DR: Change "cplusplus": true to "cplusplus": false in your llcppg.cfg. The clang-c headers are C headers, not C++ headers, so they need to be processed in C mode.