c/os: fork/exec

internal/lib/internal/syscall/execenv/execenv_default.go

@@ -0,0 +1,20 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !windows
+
+package execenv
+
+// llgo:skipall
+import "syscall"
+
+// Default will return the default environment
+// variables based on the process attributes
+// provided.
+//
+// Defaults to syscall.Environ() on all platforms
+// other than Windows.
+func Default(sys *syscall.SysProcAttr) ([]string, error) {
+	return syscall.Environ(), nil
+}

internal/lib/internal/syscall/execenv/execenv_windows.go

@@ -0,0 +1,48 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build windows
+
+package execenv
+
+// llgo:skipall
+import (
+	"internal/syscall/windows"
+	"syscall"
+	"unsafe"
+)
+
+// Default will return the default environment
+// variables based on the process attributes
+// provided.
+//
+// If the process attributes contain a token, then
+// the environment variables will be sourced from
+// the defaults for that user token, otherwise they
+// will be sourced from syscall.Environ().
+func Default(sys *syscall.SysProcAttr) (env []string, err error) {
+	if sys == nil || sys.Token == 0 {
+		return syscall.Environ(), nil
+	}
+	var blockp *uint16
+	err = windows.CreateEnvironmentBlock(&blockp, sys.Token, false)
+	if err != nil {
+		return nil, err
+	}
+	defer windows.DestroyEnvironmentBlock(blockp)
+
+	const size = unsafe.Sizeof(*blockp)
+	for *blockp != 0 { // environment block ends with empty string
+		// find NUL terminator
+		end := unsafe.Add(unsafe.Pointer(blockp), size)
+		for *(*uint16)(end) != 0 {
+			end = unsafe.Add(end, size)
+		}
+
+		entry := unsafe.Slice(blockp, (uintptr(end)-uintptr(unsafe.Pointer(blockp)))/2)
+		env = append(env, syscall.UTF16ToString(entry))
+		blockp = (*uint16)(unsafe.Add(end, size))
+	}
+	return
+}