cmd/cgo: support niladic function-like macros

Currently, cgo supports only macros which can be reduced to constants
or variables. The CL addresses remaining parts, macros which can be
represented as niladic functions.

The basic idea is simple:
  1. make a thin wrapper function per macros.
  2. replace macro expansions with function calls.

Fixes #10715
Fixes #18720

Change-Id: I150b4fb48e9dc4cc34466ef6417c04ac93d4bc1a
Reviewed-on: https://go-review.googlesource.com/43970
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/progs/run.go

@@ -219,12 +219,5 @@ func fixcgo() {
 		// cgo1 and cgo2 don't run on netbsd, srandom has a different signature
 		skipTest("cgo1")
 		skipTest("cgo2")
-		// cgo3 and cgo4 don't run on netbsd, since cgo cannot handle stdout correctly, see issue #10715.
-		skipTest("cgo3")
-		skipTest("cgo4")
-	case "openbsd", "solaris":
-		// cgo3 and cgo4 don't run on openbsd and solaris, since cgo cannot handle stdout correctly, see issue #10715.
-		skipTest("cgo3")
-		skipTest("cgo4")
 	}
 }

misc/cgo/test/issue18720.go

@@ -12,13 +12,39 @@ package cgotest
 struct foo { char c; };
 #define SIZE_OF(x) sizeof(x)
 #define SIZE_OF_FOO SIZE_OF(struct foo)
+#define VAR1 VAR
+#define VAR var
+int var = 5;
+
+#define ADDR &var
+
+#define CALL fn()
+int fn(void) {
+	return ++var;
+}
 */
 import "C"
 import "testing"
 
 func test18720(t *testing.T) {
-	if C.HELLO_WORLD != "hello\000world" {
-		t.Fatalf(`expected "hello\000world", but got %q`, C.HELLO_WORLD)
+	if got, want := C.HELLO_WORLD, "hello\000world"; got != want {
+		t.Errorf("C.HELLO_WORLD == %q, expected %q", got, want)
+	}
+
+	if got, want := C.VAR1, C.int(5); got != want {
+		t.Errorf("C.VAR1 == %v, expected %v", got, want)
+	}
+
+	if got, want := *C.ADDR, C.int(5); got != want {
+		t.Errorf("*C.ADDR == %v, expected %v", got, want)
+	}
+
+	if got, want := C.CALL, C.int(6); got != want {
+		t.Errorf("C.CALL == %v, expected %v", got, want)
+	}
+
+	if got, want := C.CALL, C.int(7); got != want {
+		t.Errorf("C.CALL == %v, expected %v", got, want)
 	}
 
 	// Issue 20125.

src/cmd/cgo/gcc.go

@@ -264,10 +264,6 @@ func (p *Package) guessKinds(f *File) []*Name {
 			if n.IsConst() {
 				continue
 			}
-
-			if isName(n.Define) {
-				n.C = n.Define
-			}
 		}
 
 		// If this is a struct, union, or enum type name, no need to guess the kind.
@@ -1073,7 +1069,17 @@ func (p *Package) rewriteRef(f *File) {
 	// Assign mangled names.
 	for _, n := range f.Name {
 		if n.Kind == "not-type" {
+			if n.Define == "" {
 				n.Kind = "var"
+			} else {
+				n.Kind = "macro"
+				n.FuncType = &FuncType{
+					Result: n.Type,
+					Go: &ast.FuncType{
+						Results: &ast.FieldList{List: []*ast.Field{{Type: n.Type.Go}}},
+					},
+				}
+			}
 		}
 		if n.Mangle == "" {
 			p.mangleName(n)
@@ -1127,7 +1133,8 @@ func (p *Package) rewriteRef(f *File) {
 				break
 			}
 		case "expr":
-			if r.Name.Kind == "func" {
+			switch r.Name.Kind {
+			case "func":
 				if builtinDefs[r.Name.C] != "" {
 					error_(r.Pos(), "use of builtin '%s' not in function call", fixGo(r.Name.C))
 				}
@@ -1154,24 +1161,24 @@ func (p *Package) rewriteRef(f *File) {
 					Fun:  &ast.Ident{NamePos: (*r.Expr).Pos(), Name: "_Cgo_ptr"},
 					Args: []ast.Expr{ast.NewIdent(name.Mangle)},
 				}
-			} else if r.Name.Kind == "type" {
+			case "type":
 				// Okay - might be new(T)
 				if r.Name.Type == nil {
 					error_(r.Pos(), "expression C.%s: undefined C type '%s'", fixGo(r.Name.Go), r.Name.C)
 					break
 				}
 				expr = r.Name.Type.Go
-			} else if r.Name.Kind == "var" {
+			case "var":
 				expr = &ast.StarExpr{Star: (*r.Expr).Pos(), X: expr}
+			case "macro":
+				expr = &ast.CallExpr{Fun: expr}
 			}
-
 		case "selector":
 			if r.Name.Kind == "var" {
 				expr = &ast.StarExpr{Star: (*r.Expr).Pos(), X: expr}
 			} else {
 				error_(r.Pos(), "only C variables allowed in selector expression %s", fixGo(r.Name.Go))
 			}
-
 		case "type":
 			if r.Name.Kind != "type" {
 				error_(r.Pos(), "expression C.%s used as type", fixGo(r.Name.Go))

src/cmd/cgo/main.go

@@ -89,7 +89,7 @@ type Name struct {
 	Mangle   string // name used in generated Go
 	C        string // name used in C
 	Define   string // #define expansion
-	Kind     string // "iconst", "uconst", "fconst", "sconst", "type", "var", "fpvar", "func", "not-type"
+	Kind     string // "iconst", "uconst", "fconst", "sconst", "type", "var", "fpvar", "func", "macro", "not-type"
 	Type     *Type  // the type of xxx
 	FuncType *FuncType
 	AddError bool

src/cmd/cgo/out.go

@@ -400,11 +400,13 @@ func (p *Package) writeDefsFunc(fgo2 io.Writer, n *Name, callsMalloc *bool) {
 	inProlog := builtinDefs[name] != ""
 	cname := fmt.Sprintf("_cgo%s%s", cPrefix, n.Mangle)
 	paramnames := []string(nil)
+	if d.Type.Params != nil {
 		for i, param := range d.Type.Params.List {
 			paramName := fmt.Sprintf("p%d", i)
 			param.Names = []*ast.Ident{ast.NewIdent(paramName)}
 			paramnames = append(paramnames, paramName)
 		}
+	}
 
 	if *gccgo {
 		// Gccgo style hooks.
@@ -502,9 +504,11 @@ func (p *Package) writeDefsFunc(fgo2 io.Writer, n *Name, callsMalloc *bool) {
 		fmt.Fprintf(fgo2, "\tif errno != 0 { r2 = syscall.Errno(errno) }\n")
 	}
 	fmt.Fprintf(fgo2, "\tif _Cgo_always_false {\n")
+	if d.Type.Params != nil {
 		for i := range d.Type.Params.List {
 			fmt.Fprintf(fgo2, "\t\t_Cgo_use(p%d)\n", i)
 		}
+	}
 	fmt.Fprintf(fgo2, "\t}\n")
 	fmt.Fprintf(fgo2, "\treturn\n")
 	fmt.Fprintf(fgo2, "}\n")
@@ -615,6 +619,9 @@ func (p *Package) writeOutputFunc(fgcc *os.File, n *Name) {
 			fmt.Fprint(fgcc, "(__typeof__(a->r)) ")
 		}
 	}
+	if n.Kind == "macro" {
+		fmt.Fprintf(fgcc, "%s;\n", n.C)
+	} else {
 		fmt.Fprintf(fgcc, "%s(", n.C)
 		for i := range n.FuncType.Params {
 			if i > 0 {
@@ -623,6 +630,7 @@ func (p *Package) writeOutputFunc(fgcc *os.File, n *Name) {
 			fmt.Fprintf(fgcc, "a->p%d", i)
 		}
 		fmt.Fprintf(fgcc, ");\n")
+	}
 	if n.AddError {
 		fmt.Fprintf(fgcc, "\t_cgo_errno = errno;\n")
 	}