runtime: implement command line arguments in hosted environments

Implement command line arguments for Linux, MacOS and WASI.

interp/interpreter.go

@@ -196,7 +196,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				// which case this call won't even get to this point but will
 				// already be emitted in initAll.
 				continue
-			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet":
+			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet" || callFn.name == "os.runtime_args":
 				// These functions should be run at runtime. Specifically:
 				//   * Print and panic functions are best emitted directly without
 				//     interpreting them, otherwise we get a ton of putchar (etc.)
@@ -204,6 +204,9 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				//   * runtime.hashmapGet tries to access the map value directly.
 				//     This is not possible as the map value is treated as a special
 				//     kind of object in this package.
+				//   * os.runtime_args reads globals that are initialized outside
+				//     the view of the interp package so it always needs to be run
+				//     at runtime.
 				err := r.runAtRuntime(fn, inst, locals, &mem, indent)
 				if err != nil {
 					return nil, mem, err

main_test.go

@@ -127,7 +127,7 @@ func TestCompiler(t *testing.T) {
 			t.Parallel()
 			runTestWithConfig("stdlib.go", "", t, &compileopts.Options{
 				Opt: "1",
-			}, nil)
+			}, nil, nil)
 		})
 
 		// Test with only the bare minimum of optimizations enabled.
@@ -136,7 +136,7 @@ func TestCompiler(t *testing.T) {
 			t.Parallel()
 			runTestWithConfig("print.go", "", t, &compileopts.Options{
 				Opt: "0",
-			}, nil)
+			}, nil, nil)
 		})
 
 		t.Run("ldflags", func(t *testing.T) {
@@ -148,7 +148,7 @@ func TestCompiler(t *testing.T) {
 						"someGlobal": "foobar",
 					},
 				},
-			}, nil)
+			}, nil, nil)
 		})
 	})
 }
@@ -160,17 +160,17 @@ func runPlatTests(target string, tests []string, t *testing.T) {
 		name := name // redefine to avoid race condition
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
-			runTest(name, target, t, nil)
+			runTest(name, target, t, nil, nil)
 		})
 	}
 	if target == "wasi" || target == "" {
 		t.Run("filesystem.go", func(t *testing.T) {
 			t.Parallel()
-			runTest("filesystem.go", target, t, nil)
+			runTest("filesystem.go", target, t, nil, nil)
 		})
 		t.Run("env.go", func(t *testing.T) {
 			t.Parallel()
-			runTest("env.go", target, t, []string{"ENV1=VALUE1", "ENV2=VALUE2"})
+			runTest("env.go", target, t, []string{"first", "second"}, []string{"ENV1=VALUE1", "ENV2=VALUE2"})
 		})
 	}
 }
@@ -187,7 +187,7 @@ func runBuild(src, out string, opts *compileopts.Options) error {
 	return Build(src, out, opts)
 }
 
-func runTest(name, target string, t *testing.T, environmentVars []string) {
+func runTest(name, target string, t *testing.T, cmdArgs, environmentVars []string) {
 	options := &compileopts.Options{
 		Target:     target,
 		Opt:        "z",
@@ -198,10 +198,10 @@ func runTest(name, target string, t *testing.T, environmentVars []string) {
 		PrintSizes: "",
 		WasmAbi:    "",
 	}
-	runTestWithConfig(name, target, t, options, environmentVars)
+	runTestWithConfig(name, target, t, options, cmdArgs, environmentVars)
 }
 
-func runTestWithConfig(name, target string, t *testing.T, options *compileopts.Options, environmentVars []string) {
+func runTestWithConfig(name, target string, t *testing.T, options *compileopts.Options, cmdArgs, environmentVars []string) {
 	// Get the expected output for this test.
 	// Note: not using filepath.Join as it strips the path separator at the end
 	// of the path.
@@ -244,6 +244,7 @@ func runTestWithConfig(name, target string, t *testing.T, options *compileopts.O
 	if target == "" {
 		cmd = exec.Command(binary)
 		cmd.Env = append(cmd.Env, environmentVars...)
+		cmd.Args = append(cmd.Args, cmdArgs...)
 	} else {
 		spec, err := compileopts.LoadTarget(target)
 		if err != nil {
@@ -257,11 +258,12 @@ func runTestWithConfig(name, target string, t *testing.T, options *compileopts.O
 		}
 
 		if len(spec.Emulator) != 0 && spec.Emulator[0] == "wasmtime" {
+			// Allow reading from the current directory.
+			cmd.Args = append(cmd.Args, "--dir=.")
 			for _, v := range environmentVars {
 				cmd.Args = append(cmd.Args, "--env", v)
 			}
-			// Allow reading from the current directory.
-			cmd.Args = append(cmd.Args, "--dir=.")
+			cmd.Args = append(cmd.Args, cmdArgs...)
 		} else {
 			cmd.Env = append(cmd.Env, environmentVars...)
 		}

src/runtime/runtime.go

@@ -23,7 +23,9 @@ func GOROOT() string {
 	return "/usr/local/go"
 }
 
-// TODO: fill with real args.
+// This is the default set of arguments, if nothing else has been set.
+// This may be overriden by modifying this global at runtime init (for example,
+// on Linux where there are real command line arguments).
 var args = []string{"/proc/self/exe"}
 
 //go:linkname os_runtime_args os.runtime_args
@@ -47,6 +49,9 @@ func memmove(dst, src unsafe.Pointer, size uintptr)
 // llvm.memset.p0i8.i32(ptr, 0, size, false).
 func memzero(ptr unsafe.Pointer, size uintptr)
 
+//export strlen
+func strlen(ptr unsafe.Pointer) uintptr
+
 // Compare two same-size buffers for equality.
 func memequal(x, y unsafe.Pointer, n uintptr) bool {
 	for i := uintptr(0); i < n; i++ {

src/runtime/runtime_unix.go

@@ -43,9 +43,34 @@ func postinit() {}
 
 // Entry point for Go. Initialize all packages and call main.main().
 //export main
-func main() int {
+func main(argc int32, argv *unsafe.Pointer) int {
 	preinit()
 
+	// Make args global big enough so that it can store all command line
+	// arguments. Unfortunately this has to be done with some magic as the heap
+	// is not yet initialized.
+	argsSlice := (*struct {
+		ptr unsafe.Pointer
+		len uintptr
+		cap uintptr
+	})(unsafe.Pointer(&args))
+	argsSlice.ptr = malloc(uintptr(argc) * (unsafe.Sizeof(uintptr(0))) * 3)
+	argsSlice.len = 0
+	argsSlice.cap = uintptr(argc)
+
+	// Initialize command line parameters.
+	for *argv != nil {
+		// Convert the C string to a Go string.
+		length := strlen(*argv)
+		argString := _string{
+			length: length,
+			ptr:    (*byte)(*argv),
+		}
+		args = append(args, *(*string)(unsafe.Pointer(&argString)))
+		// This is the Go equivalent of "argc++" in C.
+		argv = (*unsafe.Pointer)(unsafe.Pointer(uintptr(unsafe.Pointer(argv)) + unsafe.Sizeof(argv)))
+	}
+
 	// Obtain the initial stack pointer right before calling the run() function.
 	// The run function has been moved to a separate (non-inlined) function so
 	// that the correct stack pointer is read.
@@ -65,9 +90,6 @@ func runMain() {
 //go:extern environ
 var environ *unsafe.Pointer
 
-//export strlen
-func strlen(ptr unsafe.Pointer) uintptr
-
 //go:linkname syscall_runtime_envs syscall.runtime_envs
 func syscall_runtime_envs() []string {
 	// Count how many environment variables there are.

src/runtime/runtime_wasm_js.go

@@ -15,6 +15,11 @@ func _start() {
 	run()
 }
 
+//go:linkname syscall_runtime_envs syscall.runtime_envs
+func syscall_runtime_envs() []string {
+	return nil
+}
+
 var handleEvent func()
 
 //go:linkname setEventHandler syscall/js.setEventHandler

src/runtime/runtime_wasm_wasi.go

@@ -21,6 +21,33 @@ func _start() {
 	run()
 }
 
+// Read the command line arguments from WASI.
+// For example, they can be passed to a program with wasmtime like this:
+//
+//     wasmtime ./program.wasm arg1 arg2
+func init() {
+	// Read the number of args (argc) and the buffer size required to store all
+	// these args (argv).
+	var argc, argv_buf_size uint32
+	args_sizes_get(&argc, &argv_buf_size)
+
+	// Obtain the command line arguments
+	argsSlice := make([]unsafe.Pointer, argc)
+	buf := make([]byte, argv_buf_size)
+	args_get(&argsSlice[0], unsafe.Pointer(&buf[0]))
+
+	// Convert the array of C strings to an array of Go strings.
+	args = make([]string, argc)
+	for i, cstr := range argsSlice {
+		length := strlen(cstr)
+		argString := _string{
+			length: length,
+			ptr:    (*byte)(cstr),
+		}
+		args[i] = *(*string)(unsafe.Pointer(&argString))
+	}
+}
+
 func ticksToNanoseconds(ticks timeUnit) int64 {
 	return int64(ticks)
 }
@@ -62,7 +89,15 @@ func ticks() timeUnit {
 	return timeUnit(nano)
 }
 
-// Implementations of wasi_unstable APIs
+// Implementations of WASI APIs
+
+//go:wasm-module wasi_snapshot_preview1
+//export args_get
+func args_get(argv *unsafe.Pointer, argv_buf unsafe.Pointer) (errno uint16)
+
+//go:wasm-module wasi_snapshot_preview1
+//export args_sizes_get
+func args_sizes_get(argc *uint32, argv_buf_size *uint32) (errno uint16)
 
 //go:wasm-module wasi_snapshot_preview1
 //export clock_time_get

testdata/env.go

@@ -5,10 +5,19 @@ import (
 )
 
 func main() {
+	// Check for environment variables (set by the test runner).
 	println("ENV1:", os.Getenv("ENV1"))
 	v, ok := os.LookupEnv("ENV2")
 	if !ok {
 		println("ENV2 not found")
 	}
 	println("ENV2:", v)
+
+	// Check for command line arguments.
+	// Argument 0 is skipped because it is the program name, which varies by
+	// test run.
+	println()
+	for _, arg := range os.Args[1:] {
+		println("arg:", arg)
+	}
 }

testdata/env.txt

@@ -1,2 +1,5 @@
 ENV1: VALUE1
 ENV2: VALUE2
+
+arg: first
+arg: second