Improved Windows support

examples/winapi/winapi.q

@@ -0,0 +1,10 @@
+import mem
+
+main() {
+	text := mem.alloc(4)
+	text[0] = 'H'
+	text[1] = 'i'
+	text[2] = '!'
+	user32.MessageBoxA(0, text, text, 0x00240040)
+	mem.free(text, 4)
+}

lib/mem/alloc_windows.q

@@ -0,0 +1,5 @@
+import sys
+
+alloc(length Int) -> Pointer {
+	return sys.mmap(0, length, 0x0004, 0x3000)
+}

lib/sys/sys_windows.q

@@ -8,6 +8,10 @@ mmap(address Int, length Int, protection Int, flags Int) -> Pointer {
 	return kernel32.VirtualAlloc(address, length, flags, protection)
 }
 
+munmap(address Pointer, length Int) -> Int {
+	return kernel32.VirtualFree(address, length, 0x4000)
+}
+
 exit(code Int) {
 	kernel32.ExitProcess(code)
 }

src/arch/x64/AlignStack.go

@@ -0,0 +1,6 @@
+package x64
+
+// AlignStack aligns RSP on a 16-byte boundary.
+func AlignStack(code []byte) []byte {
+	return append(code, 0x48, 0x83, 0xE4, 0xF0)
+}

src/asm/Finalize.go

@@ -126,11 +126,13 @@ func (a Assembler) Finalize(dlls dll.List) ([]byte, []byte) {
 
 		case DLLCALL:
 			size := 4
-
+			// TODO: R15 could be in use.
+			code = x64.MoveRegisterRegister(code, x64.R15, x64.RSP)
+			code = x64.AlignStack(code)
 			code = x64.SubRegisterNumber(code, x64.RSP, 32)
 			code = x64.CallAtAddress(code, 0x00_00_00_00)
 			position := len(code) - size
-			code = x64.AddRegisterNumber(code, x64.RSP, 32)
+			code = x64.MoveRegisterRegister(code, x64.RSP, x64.R15)
 
 			label := x.Data.(*Label)
 			pointer := &Pointer{

src/compiler/Result.go

@@ -50,7 +50,6 @@ func (r *Result) finalize() ([]byte, []byte, dll.List) {
 		final.RegisterNumber(asm.MOVE, x64.SyscallInputRegisters[1], 0)
 		final.Syscall()
 	case "windows":
-		final.RegisterNumber(asm.SUB, x64.RSP, 8)
 		final.RegisterNumber(asm.MOVE, windows.X64InputRegisters[0], 0)
 		final.DLLCall("kernel32.ExitProcess")
 	}
@@ -83,9 +82,8 @@ func (r *Result) finalize() ([]byte, []byte, dll.List) {
 		final.RegisterNumber(asm.MOVE, x64.SyscallInputRegisters[1], 1)
 		final.Syscall()
 	case "windows":
-		final.RegisterNumber(asm.SUB, x64.RSP, 8)
 		final.RegisterNumber(asm.MOVE, windows.X64InputRegisters[0], 1)
-		final.Label(asm.DLLCALL, "kernel32.ExitProcess")
+		final.DLLCall("kernel32.ExitProcess")
 	}
 
 	code, data := final.Finalize(dlls)

src/dll/List.go

@@ -5,7 +5,7 @@ type List []DLL
 
 // Append adds a function for the given DLL if it doesn't exist yet.
 func (list List) Append(dllName string, funcName string) List {
-	for _, dll := range list {
+	for i, dll := range list {
 		if dll.Name != dllName {
 			continue
 		}
@@ -16,13 +16,24 @@ func (list List) Append(dllName string, funcName string) List {
 			}
 		}
 
-		dll.Functions = append(dll.Functions, funcName)
+		list[i].Functions = append(list[i].Functions, funcName)
 		return list
 	}
 
 	return append(list, DLL{Name: dllName, Functions: []string{funcName}})
 }
 
+// Contains returns true if the library exists.
+func (list List) Contains(dllName string) bool {
+	for _, dll := range list {
+		if dll.Name == dllName {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Index returns the position of the given function name.
 func (list List) Index(dllName string, funcName string) int {
 	index := 0

src/exe/pe/EXE.go

@@ -31,6 +31,12 @@ func Write(writer io.Writer, code []byte, data []byte, dlls dll.List) {
 	dataStart, dataPadding := exe.Align(codeStart+len(code), config.Align)
 	importsStart, importsPadding := exe.Align(dataStart+len(data), config.Align)
 
+	subSystem := IMAGE_SUBSYSTEM_WINDOWS_CUI
+
+	if dlls.Contains("user32") {
+		subSystem = IMAGE_SUBSYSTEM_WINDOWS_GUI
+	}
+
 	imports := make([]uint64, 0)
 	dllData := make([]byte, 0)
 	dllImports := []DLLImport{}
@@ -125,7 +131,7 @@ func Write(writer io.Writer, code []byte, data []byte, dlls dll.List) {
 			SizeOfImage:                 uint32(imageSize),
 			SizeOfHeaders:               config.CodeOffset, // section bodies begin here
 			CheckSum:                    0,
-			Subsystem:                   IMAGE_SUBSYSTEM_WINDOWS_CUI,
+			Subsystem:                   uint16(subSystem),
 			DllCharacteristics:          IMAGE_DLLCHARACTERISTICS_HIGH_ENTROPY_VA | IMAGE_DLLCHARACTERISTICS_NX_COMPAT | IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE, // IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE
 			SizeOfStackReserve:          0x100000,
 			SizeOfStackCommit:           0x1000,