cgo: supports //export functions only calls in C

cl/_testgo/cgofull/cgofull.go

@@ -94,8 +94,11 @@ static void test_callback(Cb cb) {
 	printf("done\n");
 }
 
+extern int go_callback_not_use_in_go(int);
+
 static void run_callback() {
 	test_callback(c_callback);
+	test_callback(go_callback_not_use_in_go);
 }
 */
 import "C"
@@ -107,6 +110,11 @@ import (
 	"github.com/goplus/llgo/cl/_testgo/cgofull/pymod2"
 )
 
+//export go_callback_not_use_in_go
+func go_callback_not_use_in_go(i C.int) C.int {
+	return i + 1
+}
+
 //export go_callback
 func go_callback(i C.int) C.int {
 	return i + 1

cl/compile.go

@@ -110,10 +110,11 @@ type context struct {
 	inCFunc bool
 	skipall bool
 
-	cgoCalled bool
-	cgoArgs   []llssa.Expr
-	cgoRet    llssa.Expr
-	cgoFuncs  map[string][]string
+	cgoCalled  bool
+	cgoArgs    []llssa.Expr
+	cgoRet     llssa.Expr
+	cgoSymbols []string
+	cgoExports map[string]string
 }
 
 type pkgState byte
@@ -415,14 +416,6 @@ func (p *context) compileBlock(b llssa.Builder, block *ssa.BasicBlock, n int, do
 		callRuntimeInit(b, pkg)
 		b.Call(pkg.FuncOf("main.init").Expr)
 	}
-	fname := p.goProg.Fset.Position(block.Parent().Pos()).Filename
-	if p.cgoFuncs == nil {
-		p.cgoFuncs = make(map[string][]string)
-	}
-	var cgoFuncs []string
-	if funcs, ok := p.cgoFuncs[fname]; ok {
-		cgoFuncs = funcs
-	}
 	fnName := block.Parent().Name()
 	cgoReturned := false
 	isCgoCfunc := isCgoCfunc(fnName)
@@ -442,8 +435,7 @@ func (p *context) compileBlock(b llssa.Builder, block *ssa.BasicBlock, n int, do
 				// load cgo function pointer
 				varName := instr.X.Name()
 				if instr.Op == token.MUL && strings.HasPrefix(varName, "_cgo_") {
-					cgoFuncs = append(cgoFuncs, varName)
-					p.cgoFuncs[fname] = cgoFuncs
+					p.cgoSymbols = append(p.cgoSymbols, varName)
 					p.compileInstr(b, instr)
 				}
 			case *ssa.Call:
@@ -925,13 +917,7 @@ func (p *context) compileValue(b llssa.Builder, v ssa.Value) llssa.Expr {
 		varName := v.Name()
 		val := p.varOf(b, v)
 		if isCgoVar(varName) {
-			fname := p.fset.Position(v.Pos()).Filename
-			funcs, ok := p.cgoFuncs[fname]
-			if !ok {
-				funcs = make([]string, 0, 1)
-			}
-			funcs = append(funcs, val.Name())
-			p.cgoFuncs[fname] = funcs
+			p.cgoSymbols = append(p.cgoSymbols, val.Name())
 		}
 		if debugSymbols {
 			pos := p.fset.Position(v.Pos())
@@ -1001,7 +987,7 @@ func NewPackage(prog llssa.Program, pkg *ssa.Package, files []*ast.File) (ret ll
 }
 
 // NewPackageEx compiles a Go package to LLVM IR package.
-func NewPackageEx(prog llssa.Program, patches Patches, pkg *ssa.Package, files []*ast.File) (ret llssa.Package, externs map[string][]string, err error) {
+func NewPackageEx(prog llssa.Program, patches Patches, pkg *ssa.Package, files []*ast.File) (ret llssa.Package, externs []string, err error) {
 	pkgProg := pkg.Prog
 	pkgTypes := pkg.Pkg
 	oldTypes := pkgTypes
@@ -1033,6 +1019,8 @@ func NewPackageEx(prog llssa.Program, patches Patches, pkg *ssa.Package, files [
 		loaded: map[*types.Package]*pkgInfo{
 			types.Unsafe: {kind: PkgDeclOnly}, // TODO(xsw): PkgNoInit or PkgDeclOnly?
 		},
+		cgoExports: make(map[string]string),
+		cgoSymbols: make([]string, 0, 128),
 	}
 	ctx.initPyModule()
 	ctx.initFiles(pkgPath, files)
@@ -1066,25 +1054,11 @@ func NewPackageEx(prog llssa.Program, patches Patches, pkg *ssa.Package, files [
 		ctx.initAfter = nil
 		fn()
 	}
-	externs = ctx.cgoFuncs
-	// TODO(lijie): read export name
-	for _, funcs := range externs {
-		for _, funcName := range funcs {
-			if strings.Contains(funcName, ".__cgo_") {
-				goFnName := strings.Replace(funcName, ".__cgo_", ".", 1)
-				idx := strings.LastIndex(funcName, ".__cgo_")
-				cfuncName := funcName[idx+len(".__cgo_"):]
-				v := ret.VarOf(funcName)
-				if fn := ret.FuncOf(goFnName); fn != nil {
-					// TODO(lijie): naive go:export, need better way from comment
-					fn.SetName(cfuncName)
-					// Replace symbol instead of static linking
-					v.ReplaceAllUsesWith(fn.Expr)
-				} else if fn := ret.FuncOf(cfuncName); fn != nil {
-					// Replace symbol instead of static linking
-					v.ReplaceAllUsesWith(fn.Expr)
-				}
-			}
+	externs = ctx.cgoSymbols
+	for fnName, exportName := range ctx.cgoExports {
+		fn := ret.FuncOf(fnName)
+		if fn != nil {
+			fn.SetName(exportName)
 		}
 	}
 	return

cl/import.go

@@ -246,16 +246,26 @@ func (p *context) initLinknameByDoc(doc *ast.CommentGroup, fullName, inPkgName s
 
 func (p *context) initLinkname(line string, f func(inPkgName string) (fullName string, isVar, ok bool)) {
 	const (
-		linkname  = "//go:linkname "
-		llgolink  = "//llgo:link "
-		llgolink2 = "// llgo:link "
+		linkname   = "//go:linkname "
+		llgolink   = "//llgo:link "
+		llgolink2  = "// llgo:link "
+		exportName = "//export "
 	)
 	if strings.HasPrefix(line, linkname) {
 		p.initLink(line, len(linkname), f)
 	} else if strings.HasPrefix(line, llgolink2) {
 		p.initLink(line, len(llgolink2), f)
 	} else if strings.HasPrefix(line, llgolink) {
 		p.initLink(line, len(llgolink), f)
+	} else if strings.HasPrefix(line, exportName) {
+		p.initCgoExport(line, len(exportName), f)
+	}
+}
+
+func (p *context) initCgoExport(line string, prefix int, f func(inPkgName string) (fullName string, isVar, ok bool)) {
+	name := strings.TrimSpace(line[prefix:])
+	if fullName, _, ok := f(name); ok {
+		p.cgoExports[fullName] = name
 	}
 }
 

internal/build/cgo.go

@@ -53,7 +53,7 @@ static void* _Cmalloc(size_t size) {
 `
 )
 
-func buildCgo(ctx *context, pkg *aPackage, files []*ast.File, externs map[string][]string, verbose bool) (cgoLdflags []string, err error) {
+func buildCgo(ctx *context, pkg *aPackage, files []*ast.File, externs []string, verbose bool) (cgoLdflags []string, err error) {
 	cfiles, preambles, cdecls, err := parseCgo_(pkg, files)
 	if err != nil {
 		return
@@ -93,26 +93,24 @@ func buildCgo(ctx *context, pkg *aPackage, files []*ast.File, externs map[string
 	re := regexp.MustCompile(`^(_cgo_[^_]+_(Cfunc|Cmacro)_)(.*)$`)
 	cgoSymbols := make(map[string]string)
 	mallocFix := false
-	for _, symbols := range externs {
-		for _, symbolName := range symbols {
-			lastPart := symbolName
-			lastDot := strings.LastIndex(symbolName, ".")
-			if lastDot != -1 {
-				lastPart = symbolName[lastDot+1:]
-			}
-			if strings.HasPrefix(lastPart, "__cgo_") {
-				// func ptr var: main.__cgo_func_name
-				cgoSymbols[symbolName] = lastPart
-			} else if m := re.FindStringSubmatch(symbolName); len(m) > 0 {
-				prefix := m[1] // _cgo_hash_(Cfunc|Cmacro)_
-				name := m[3]   // remaining part
-				cgoSymbols[symbolName] = name
-				// fix missing _cgo_9113e32b6599_Cfunc__Cmalloc
-				if !mallocFix && m[2] == "Cfunc" {
-					mallocName := prefix + "_Cmalloc"
-					cgoSymbols[mallocName] = "_Cmalloc"
-					mallocFix = true
-				}
+	for _, symbolName := range externs {
+		lastPart := symbolName
+		lastDot := strings.LastIndex(symbolName, ".")
+		if lastDot != -1 {
+			lastPart = symbolName[lastDot+1:]
+		}
+		if strings.HasPrefix(lastPart, "__cgo_") {
+			// func ptr var: main.__cgo_func_name
+			cgoSymbols[symbolName] = lastPart
+		} else if m := re.FindStringSubmatch(symbolName); len(m) > 0 {
+			prefix := m[1] // _cgo_hash_(Cfunc|Cmacro)_
+			name := m[3]   // remaining part
+			cgoSymbols[symbolName] = name
+			// fix missing _cgo_9113e32b6599_Cfunc__Cmalloc
+			if !mallocFix && m[2] == "Cfunc" {
+				mallocName := prefix + "_Cmalloc"
+				cgoSymbols[mallocName] = "_Cmalloc"
+				mallocFix = true
 			}
 		}
 	}
@@ -170,10 +168,16 @@ func genExternDeclsByClang(pkg *aPackage, src string, cflags []string, cgoSymbol
 	var toRemove []string
 	for cgoName, symbolName := range cgoSymbols {
 		if strings.HasPrefix(symbolName, "__cgo_") {
-			cfuncName := symbolName[len("__cgo_"):]
-			cfn := pkg.LPkg.NewFunc(cfuncName, types.NewSignature(nil, nil, nil, false), llssa.InC)
+			gofuncName := strings.Replace(cgoName, ".__cgo_", ".", 1)
+			gofn := pkg.LPkg.FuncOf(gofuncName)
 			cgoVar := pkg.LPkg.VarOf(cgoName)
-			cgoVar.ReplaceAllUsesWith(cfn.Expr)
+			if gofn != nil {
+				cgoVar.ReplaceAllUsesWith(gofn.Expr)
+			} else {
+				cfuncName := symbolName[len("__cgo_"):]
+				cfn := pkg.LPkg.NewFunc(cfuncName, types.NewSignatureType(nil, nil, nil, nil, nil, false), llssa.InC)
+				cgoVar.ReplaceAllUsesWith(cfn.Expr)
+			}
 			toRemove = append(toRemove, cgoName)
 		} else {
 			usePtr := ""