Implemented running executables in memory

go.mod

@@ -7,4 +7,4 @@ require (
 	git.urbach.dev/go/color v0.0.0-20250606151219-222306e0b534
 )
 
-require golang.org/x/sys v0.33.0 // indirect
+require golang.org/x/sys v0.33.0

src/cli/help.txt

@@ -9,5 +9,5 @@ Commands:
         --os [os]                  cross-compile for OS: [linux|mac|windows]
         --verbose, -v              show everything
 
-    run [directory | file]         build and run the executable
+    run [directory | file]         build and run the executable in memory
     help                           show this help

src/cli/run.go

@@ -3,10 +3,10 @@ package cli
 import (
 	"fmt"
 	"os"
-	"os/exec"
 
 	"git.urbach.dev/cli/q/src/compiler"
 	"git.urbach.dev/cli/q/src/linker"
+	"git.urbach.dev/cli/q/src/memfile"
 )
 
 // run builds and runs the executable.
@@ -17,23 +17,20 @@ func run(args []string) int {
 		return exit(err)
 	}
 
-	result, err := compiler.Compile(b)
+	env, err := compiler.Compile(b)
 
 	if err != nil {
 		return exit(err)
 	}
 
-	err = linker.WriteFile(b.Executable(), b, result)
+	file, err := memfile.New(b.Executable())
 
 	if err != nil {
 		return exit(err)
 	}
 
-	cmd := exec.Command(b.Executable())
-	cmd.Stdout = os.Stdout
-	cmd.Stdin = os.Stdin
-	cmd.Stderr = os.Stderr
-	err = cmd.Run()
+	linker.Write(file, b, env)
+	err = memfile.Exec(file)
 
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)

src/linker/Write.go

@@ -0,0 +1,41 @@
+package linker
+
+import (
+	"io"
+
+	"git.urbach.dev/cli/q/src/asm"
+	"git.urbach.dev/cli/q/src/build"
+	"git.urbach.dev/cli/q/src/core"
+	"git.urbach.dev/cli/q/src/data"
+	"git.urbach.dev/cli/q/src/elf"
+	"git.urbach.dev/cli/q/src/macho"
+	"git.urbach.dev/cli/q/src/pe"
+)
+
+// Write writes an executable to the given writer.
+func Write(writer io.WriteSeeker, b *build.Build, env *core.Environment) {
+	program := asm.Assembler{
+		Instructions: make([]asm.Instruction, 0, 32),
+		Data:         make(data.Data, 32),
+	}
+
+	init := env.Functions["run.init"]
+	traversed := make(map[*core.Function]bool, len(env.Functions))
+
+	// This will place the init function immediately after the entry point
+	// and also add everything the init function calls recursively.
+	init.EachDependency(traversed, func(f *core.Function) {
+		program.Merge(&f.Assembler)
+	})
+
+	code, data, libs := program.Compile(b)
+
+	switch b.OS {
+	case build.Linux:
+		elf.Write(writer, b, code, data)
+	case build.Mac:
+		macho.Write(writer, b, code, data)
+	case build.Windows:
+		pe.Write(writer, b, code, data, libs)
+	}
+}

src/linker/WriteFile.go

@@ -3,13 +3,8 @@ package linker
 import (
 	"os"
 
-	"git.urbach.dev/cli/q/src/asm"
 	"git.urbach.dev/cli/q/src/build"
 	"git.urbach.dev/cli/q/src/core"
-	"git.urbach.dev/cli/q/src/data"
-	"git.urbach.dev/cli/q/src/elf"
-	"git.urbach.dev/cli/q/src/macho"
-	"git.urbach.dev/cli/q/src/pe"
 )
 
 // WriteFile writes an executable file to disk.
@@ -20,36 +15,12 @@ func WriteFile(executable string, b *build.Build, env *core.Environment) error {
 		return err
 	}
 
-	init := env.Functions["run.init"]
-	traversed := make(map[*core.Function]bool, len(env.Functions))
-
-	final := asm.Assembler{
-		Instructions: make([]asm.Instruction, 0, 32),
-		Data:         make(data.Data, 32),
-	}
-
-	// This will place the main function immediately after the entry point
-	// and also add everything the main function calls recursively.
-	init.EachDependency(traversed, func(f *core.Function) {
-		final.Merge(&f.Assembler)
-	})
-
-	code, data, libs := final.Compile(b)
-
-	switch b.OS {
-	case build.Linux:
-		elf.Write(file, b, code, data)
-	case build.Mac:
-		macho.Write(file, b, code, data)
-	case build.Windows:
-		pe.Write(file, b, code, data, libs)
-	}
-
-	err = file.Close()
+	Write(file, b, env)
+	err = file.Chmod(0o755)
 
 	if err != nil {
 		return err
 	}
 
-	return os.Chmod(executable, 0o755)
+	return file.Close()
 }

src/memfile/Exec_linux.go

@@ -0,0 +1,47 @@
+//go:build linux
+
+package memfile
+
+import (
+	"os"
+	"strconv"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// Exec executes an in-memory file.
+func Exec(file *os.File) error {
+	empty, err := syscall.BytePtrFromString("")
+
+	if err != nil {
+		return err
+	}
+
+	argv := []string{"/proc/self/fd/" + strconv.Itoa(int(file.Fd()))}
+	argvp, err := syscall.SlicePtrFromStrings(argv)
+
+	if err != nil {
+		return err
+	}
+
+	envv := os.Environ()
+	envvp, err := syscall.SlicePtrFromStrings(envv)
+
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := syscall.Syscall6(
+		unix.SYS_EXECVEAT,
+		uintptr(file.Fd()),
+		uintptr(unsafe.Pointer(empty)),
+		uintptr(unsafe.Pointer(&argvp[0])),
+		uintptr(unsafe.Pointer(&envvp[0])),
+		uintptr(unix.AT_EMPTY_PATH),
+		0,
+	)
+
+	return errno
+}

src/memfile/Exec_other.go

@@ -0,0 +1,29 @@
+//go:build !linux
+
+package memfile
+
+import (
+	"os"
+	"os/exec"
+)
+
+// Exec executes an in-memory file.
+func Exec(file *os.File) error {
+	err := file.Chmod(0o700)
+
+	if err != nil {
+		return err
+	}
+
+	err = file.Close()
+
+	if err != nil {
+		return err
+	}
+
+	cmd := exec.Command(file.Name())
+	cmd.Stdout = os.Stdout
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}

src/memfile/New_linux.go

@@ -0,0 +1,21 @@
+//go:build linux
+
+package memfile
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// New creates a new anonymous in-memory file.
+func New(name string) (*os.File, error) {
+	fd, err := unix.MemfdCreate(name, unix.MFD_CLOEXEC)
+
+	if err != nil {
+		return nil, err
+	}
+
+	memFile := os.NewFile(uintptr(fd), name)
+	return memFile, nil
+}

src/memfile/New_other.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package memfile
+
+import (
+	"os"
+)
+
+// New creates a new anonymous in-memory file.
+func New(name string) (*os.File, error) {
+	return os.CreateTemp("", "")
+}

src/memfile/memfile_test.go

@@ -0,0 +1,15 @@
+package memfile_test
+
+import (
+	"testing"
+
+	"git.urbach.dev/cli/q/src/memfile"
+	"git.urbach.dev/go/assert"
+)
+
+func TestNew(t *testing.T) {
+	file, err := memfile.New("")
+	assert.Nil(t, err)
+	assert.NotNil(t, file)
+	// memfile.Exec can't be tested because it would replace the test executable
+}