Improved alignment function

lib/sys/sys_windows.q

@@ -1,3 +1,7 @@
 write(_ Int, _ Pointer, _ Int) -> Int {
 	return 0
 }
+
+exit(_ Int) {
+	return
+}

src/asm/Finalize.go

@@ -337,12 +337,11 @@ restart:
 	}
 
 	data, dataLabels = a.Data.Finalize()
-
+	dataStart := config.BaseAddress + config.CodeOffset + len(code)
-	dataStart := Address(config.BaseAddress) + config.CodeOffset + Address(len(code))
+	dataStart, _ = exe.Align(dataStart, config.Align)
-	dataStart += exe.Padding(dataStart, config.Align)
 
 	for _, pointer := range dataPointers {
-		address := dataStart + pointer.Resolve()
+		address := Address(dataStart) + pointer.Resolve()
 		slice := code[pointer.Position : pointer.Position+4]
 		binary.LittleEndian.PutUint32(slice, uint32(address))
 	}

src/exe/Align.go

@@ -0,0 +1,7 @@
+package exe
+
+// Align calculates the next aligned address and the padding needed.
+func Align[T int | uint | int64 | uint64 | int32 | uint32](n T, alignment T) (T, T) {
+	aligned := (n + (alignment - 1)) & ^(alignment - 1)
+	return aligned, aligned - n
+}

src/exe/Padding.go

@@ -1,6 +0,0 @@
-package exe
-
-// Padding calculates the padding needed to align `n` bytes with the specified alignment.
-func Padding[T int | uint | int64 | uint64 | int32 | uint32](n T, align T) T {
-	return align - (n % align)
-}

src/exe/elf/ELF.go

@@ -21,10 +21,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
 	const HeaderEnd = HeaderSize + ProgramHeaderSize*2
 
 	var (
-		codePadding = exe.Padding(HeaderEnd, config.Align)
+		codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
-		codeEnd     = config.CodeOffset + len(code)
+		dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
-		dataPadding = exe.Padding(codeEnd, config.Align)
-		dataStart   = codeEnd + dataPadding
 	)
 
 	elf := &ELF{
@@ -74,11 +72,11 @@ func Write(writer io.Writer, code []byte, data []byte) {
 	binary.Write(writer, binary.LittleEndian, &elf.Header)
 	binary.Write(writer, binary.LittleEndian, &elf.CodeHeader)
 	binary.Write(writer, binary.LittleEndian, &elf.DataHeader)
-	writer.Write(bytes.Repeat([]byte{0}, codePadding))
+	writer.Write(bytes.Repeat([]byte{0x00}, codePadding))
 	writer.Write(code)
 
 	if len(data) > 0 {
-		writer.Write(bytes.Repeat([]byte{0}, dataPadding))
+		writer.Write(bytes.Repeat([]byte{0x00}, dataPadding))
 		writer.Write(data)
 	}
 }

src/exe/macho/MachO.go

@@ -26,10 +26,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
 	)
 
 	var (
-		codePadding = exe.Padding(HeaderEnd, config.Align)
+		codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
-		codeEnd     = config.CodeOffset + len(code)
+		dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
-		dataPadding = exe.Padding(codeEnd, config.Align)
-		dataStart   = codeEnd + dataPadding
 	)
 
 	m := &MachO{
@@ -61,9 +59,9 @@ func Write(writer io.Writer, code []byte, data []byte) {
 			Length:       Segment64Size,
 			Name:         [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
 			Address:      config.BaseAddress,
-			SizeInMemory: uint64(codeEnd),
+			SizeInMemory: uint64(codeStart + len(code)),
 			Offset:       0,
-			SizeInFile:   uint64(codeEnd),
+			SizeInFile:   uint64(codeStart + len(code)),
 			NumSections:  0,
 			Flag:         0,
 			MaxProt:      ProtReadable | ProtExecutable,
@@ -119,8 +117,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
 	binary.Write(writer, binary.LittleEndian, &m.DataHeader)
 	binary.Write(writer, binary.LittleEndian, &m.UnixThread)
 
-	writer.Write(bytes.Repeat([]byte{0}, int(codePadding)))
+	writer.Write(bytes.Repeat([]byte{0x00}, int(codePadding)))
 	writer.Write(code)
-	writer.Write(bytes.Repeat([]byte{0}, int(dataPadding)))
+	writer.Write(bytes.Repeat([]byte{0x00}, int(dataPadding)))
 	writer.Write(data)
 }

src/exe/pe/EXE.go

@@ -9,31 +9,36 @@ import (
 	"git.akyoto.dev/cli/q/src/exe"
 )
 
-const NumSections = 2
-
 // EXE is the portable executable format used on Windows.
 type EXE struct {
 	DOSHeader
 	NTHeader
 	OptionalHeader64
-	Sections [NumSections]SectionHeader
+	Sections []SectionHeader
 }
 
 // Write writes the EXE file to the given writer.
 func Write(writer io.Writer, code []byte, data []byte) {
-	const (
+	NumSections := 1
-		HeaderEnd = DOSHeaderSize + NTHeaderSize + OptionalHeader64Size + SectionHeaderSize*NumSections
+
-	)
+	if len(data) != 0 {
+		NumSections += 1
+	}
+
+	HeaderEnd := DOSHeaderSize + NTHeaderSize + OptionalHeader64Size + SectionHeaderSize*NumSections
 
 	var (
-		codePadding = exe.Padding(HeaderEnd, config.Align)
+		codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
-		codeEnd     = config.CodeOffset + len(code)
+		dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
-		dataPadding = exe.Padding(codeEnd, config.Align)
-		dataStart   = codeEnd + dataPadding
 	)
 
-	imageSize := dataStart + len(data)
+	imageSize := codeStart + len(code)
-	imageSize += exe.Padding(imageSize, config.Align)
+
+	if len(data) != 0 {
+		imageSize = dataStart + len(data)
+	}
+
+	imageSize, _ = exe.Align(imageSize, config.Align)
 
 	pe := &EXE{
 		DOSHeader: DOSHeader{
@@ -43,7 +48,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
 		NTHeader: NTHeader{
 			Signature:            [4]byte{'P', 'E', 0, 0},
 			Machine:              IMAGE_FILE_MACHINE_AMD64,
-			NumberOfSections:     NumSections,
+			NumberOfSections:     uint16(NumSections),
 			SizeOfOptionalHeader: OptionalHeader64Size,
 			Characteristics:      IMAGE_FILE_EXECUTABLE_IMAGE | IMAGE_FILE_LARGE_ADDRESS_AWARE,
 		},
@@ -61,7 +66,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
 			MajorSubsystemVersion:       0x06,
 			SizeOfImage:                 uint32(imageSize),
 			SizeOfHeaders:               config.CodeOffset, // section bodies begin here
-			Subsystem:                   IMAGE_SUBSYSTEM_WINDOWS_GUI,
+			Subsystem:                   IMAGE_SUBSYSTEM_WINDOWS_CUI,
 			DllCharacteristics:          IMAGE_DLLCHARACTERISTICS_HIGH_ENTROPY_VA | IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE | IMAGE_DLLCHARACTERISTICS_NX_COMPAT | IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE,
 			SizeOfStackReserve:          0x100000,
 			SizeOfStackCommit:           0x1000,
@@ -87,7 +92,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
 				{VirtualAddress: 0, Size: 0},
 			},
 		},
-		Sections: [NumSections]SectionHeader{
+		Sections: []SectionHeader{
 			{
 				Name:            [8]byte{'.', 't', 'e', 'x', 't'},
 				VirtualSize:     uint32(len(code)),
@@ -110,10 +115,13 @@ func Write(writer io.Writer, code []byte, data []byte) {
 	binary.Write(writer, binary.LittleEndian, &pe.DOSHeader)
 	binary.Write(writer, binary.LittleEndian, &pe.NTHeader)
 	binary.Write(writer, binary.LittleEndian, &pe.OptionalHeader64)
-	binary.Write(writer, binary.LittleEndian, &pe.Sections)
+	binary.Write(writer, binary.LittleEndian, pe.Sections[:NumSections])
 
-	writer.Write(bytes.Repeat([]byte{0}, int(codePadding)))
+	writer.Write(bytes.Repeat([]byte{0x00}, int(codePadding)))
 	writer.Write(code)
-	writer.Write(bytes.Repeat([]byte{0}, int(dataPadding)))
+
-	writer.Write(data)
+	if len(data) != 0 {
+		writer.Write(bytes.Repeat([]byte{0x00}, int(dataPadding)))
+		writer.Write(data)
+	}
 }

src/exe/pe/pe.md

@@ -1,5 +1,10 @@
 ## Portable Executable
 
+## Notes
+
+Unlike Linux, Windows does not ignore zero-length sections and will fail loading them because they don't exist within the file.
+Adding a single byte to the section can fix this problem, but it's easier to just remove the section header entirely.
+
 ## Links
 
 - https://learn.microsoft.com/en-us/previous-versions/ms809762(v=msdn.10)