internal/fakecgo: clean up gen.go (#235)

internal/fakecgo/doc.go

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: 2022 The Ebitengine Authors
 
-//go:build darwin || freebsd
+//go:build darwin || freebsd || linux
 
 // Package fakecgo implements the Cgo runtime (runtime/cgo) entirely in Go.
 // This allows code that calls into C to function properly when CGO_ENABLED=0.
@@ -30,4 +30,3 @@
 package fakecgo
 
 //go:generate go run gen.go
-//go:generate gofmt -s -w symbols.go

internal/fakecgo/gen.go

@@ -100,6 +100,20 @@ TEXT _{{.Name}}(SB), NOSPLIT|NOFRAME, $0-0
 {{ end -}}
 `
 
+const templateSymbolsGoos = `// Code generated by 'go generate' with gen.go. DO NOT EDIT.
+
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
+
+package fakecgo
+
+{{- range $location := . }}
+{{- range .Symbols }}
+//go:cgo_import_dynamic purego_{{ .Name }} {{ .Name }} "{{ $location.SharedObject }}"
+{{- end }}
+{{- end }}
+`
+
 type Arg struct {
 	Name string
 	Type string
@@ -111,6 +125,11 @@ type Symbol struct {
 	Return string
 }
 
+type LocatedSymbols struct {
+	SharedObject string
+	Symbols      []Symbol
+}
+
 var (
 	libcSymbols = []Symbol{
 		{"malloc", [5]Arg{{"size", "uintptr"}}, "unsafe.Pointer"},
@@ -176,36 +195,45 @@ func run() error {
 	if err := t.Execute(f, allSymbols); err != nil {
 		return err
 	}
+	t, err = template.New("symbols_goos.go").Parse(templateSymbolsGoos)
+	if err != nil {
+		return err
+	}
 	for _, goos := range []string{"darwin", "linux", "freebsd"} {
 		f, err = os.Create(fmt.Sprintf("symbols_%s.go", goos))
 		defer f.Close()
 		if err != nil {
 			return err
 		}
-		f.WriteString(`// Code generated by 'go generate' with gen.go. DO NOT EDIT.
-
-// SPDX-License-Identifier: Apache-2.0
-// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
-
-package fakecgo
-
-`)
-		const importPragma = `//go:cgo_import_dynamic purego_%s %s "%s"` + "\n"
-		libcSO := "/usr/lib/libSystem.B.dylib"
-		pthreadSO := "/usr/lib/libSystem.B.dylib"
-		if goos == "linux" {
-			libcSO = "libc.so.6"
-			pthreadSO = "libpthread.so.0"
-		} else if goos == "freebsd" {
+		b := &bytes.Buffer{}
+		var libcSO, pthreadSO string
+		switch goos {
+		case "darwin":
+			libcSO = "/usr/lib/libSystem.B.dylib"
+			pthreadSO = "/usr/lib/libSystem.B.dylib"
+		case "freebsd":
 			libcSO = "libc.so.7"
 			pthreadSO = "libpthread.so"
+		case "linux":
+			libcSO = "libc.so.6"
+			pthreadSO = "libpthread.so.0"
+		default:
+			return fmt.Errorf("unsupported OS: %s", goos)
 		}
-
-		for _, sym := range libcSymbols {
-			f.WriteString(fmt.Sprintf(importPragma, sym.Name, sym.Name, libcSO))
+		located := []LocatedSymbols{
+			{SharedObject: libcSO, Symbols: libcSymbols},
+			{SharedObject: pthreadSO, Symbols: pthreadSymbols},
+		}
+		if err = t.Execute(b, located); err != nil {
+			return err
 		}
-		for _, sym := range pthreadSymbols {
-			f.WriteString(fmt.Sprintf(importPragma, sym.Name, sym.Name, pthreadSO))
+		var src []byte
+		src, err = format.Source(b.Bytes())
+		if err != nil {
+			return err
+		}
+		if _, err = f.Write(src); err != nil {
+			return err
 		}
 	}
 	return nil