all: compile and link using clang, where possible

builtins.go

@@ -195,7 +195,7 @@ func loadBuiltins(target string) (path string, err error) {
 		objpath := filepath.Join(dir, objname+".o")
 		objs = append(objs, objpath)
 		srcpath := filepath.Join(builtinsDir, name)
-		cmd := exec.Command(commands["clang"], "-c", "-Oz", "-g", "-Werror", "-Wall", "-std=c11", "-fshort-enums", "-nostdlibinc", "--target="+target, "-o", objpath, srcpath)
+		cmd := exec.Command(commands["clang"], "-c", "-Oz", "-g", "-Werror", "-Wall", "-std=c11", "-fshort-enums", "-nostdlibinc", "-ffunction-sections", "-fdata-sections", "--target="+target, "-o", objpath, srcpath)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 		cmd.Dir = dir

docs/installation.rst

@@ -24,11 +24,10 @@ ARM LLVM backend (which is even used in the propietary C compiler from ARM).
 Compiling to object code should be supported out of the box, but compiling the
 final binary and flashing it needs some extra tools.
 
-    * binutils (``arm-none-eabi-objcopy``) for producing .hex files for
+    * binutils (``arm-none-eabi-ld``, ``arm-none-eabi-objcopy``) for linking and
-      flashing.
+      for producing .hex files for flashing.
-    * GCC (``arm-none-eabi-gcc``) for linking object files.
+    * Clang 7 (``clang-7``) for building assembly files and the `compiler
-    * Clang 7 (``clang-7``) for building the `compiler runtime library
+      runtime library <https://compiler-rt.llvm.org/>`_ .
-      <https://compiler-rt.llvm.org/>`_.
     * The flashing tool for the particular chip, like ``openocd`` or
       ``nrfjprog``.
 

main.go

@@ -10,6 +10,7 @@ import (
 	"os/exec"
 	"os/signal"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"syscall"
 
@@ -161,14 +162,30 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 			cachePath, _ = filepath.Split(librt)
 		}
 
-		// Link the object file with the system compiler.
+		// Prepare link command.
 		executable := filepath.Join(dir, "main")
 		tmppath := executable // final file
-		args := append(spec.PreLinkArgs, "-o", executable, objfile)
+		ldflags := append(spec.LDFlags, "-o", executable, objfile)
 		if spec.RTLib == "compiler-rt" {
-			args = append(args, "-L", cachePath, "-lrt-"+spec.Triple)
+			ldflags = append(ldflags, "-L", cachePath, "-lrt-"+spec.Triple)
 		}
-		cmd := exec.Command(spec.Linker, args...)
+
+		// Compile extra files.
+		for i, path := range spec.ExtraFiles {
+			outpath := filepath.Join(dir, "extra-"+strconv.Itoa(i)+"-"+filepath.Base(path)+".o")
+			cmd := exec.Command(spec.Compiler, append(spec.CFlags, "-c", "-o", outpath, path)...)
+			cmd.Stdout = os.Stdout
+			cmd.Stderr = os.Stderr
+			cmd.Dir = sourceDir()
+			err := cmd.Run()
+			if err != nil {
+				return err
+			}
+			ldflags = append(ldflags, outpath)
+		}
+
+		// Link the object files together.
+		cmd := exec.Command(spec.Linker, ldflags...)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 		cmd.Dir = sourceDir()

target.go

@@ -21,9 +21,12 @@ type TargetSpec struct {
 	Inherits   []string `json:"inherits"`
 	Triple     string   `json:"llvm-target"`
 	BuildTags  []string `json:"build-tags"`
+	Compiler   string   `json:"compiler"`
 	Linker     string   `json:"linker"`
 	RTLib      string   `json:"rtlib"` // compiler runtime library (libgcc, compiler-rt)
-	PreLinkArgs []string `json:"pre-link-args"`
+	CFlags     []string `json:"cflags"`
+	LDFlags    []string `json:"ldflags"`
+	ExtraFiles []string `json:"extra-files"`
 	Objcopy    string   `json:"objcopy"`
 	Emulator   []string `json:"emulator"`
 	Flasher    string   `json:"flash"`
@@ -41,15 +44,18 @@ func (spec *TargetSpec) copyProperties(spec2 *TargetSpec) {
 		spec.Triple = spec2.Triple
 	}
 	spec.BuildTags = append(spec.BuildTags, spec2.BuildTags...)
+	if spec2.Compiler != "" {
+		spec.Compiler = spec2.Compiler
+	}
 	if spec2.Linker != "" {
 		spec.Linker = spec2.Linker
 	}
 	if spec2.RTLib != "" {
 		spec.RTLib = spec2.RTLib
 	}
-	if len(spec2.PreLinkArgs) != 0 {
+	spec.CFlags = append(spec.CFlags, spec2.CFlags...)
-		spec.PreLinkArgs = spec2.PreLinkArgs
+	spec.LDFlags = append(spec.LDFlags, spec2.LDFlags...)
-	}
+	spec.ExtraFiles = append(spec.ExtraFiles, spec2.ExtraFiles...)
 	if spec2.Objcopy != "" {
 		spec.Objcopy = spec2.Objcopy
 	}
@@ -146,7 +152,7 @@ func LoadTarget(target string) (*TargetSpec, error) {
 			Triple:    target,
 			BuildTags: []string{runtime.GOOS, runtime.GOARCH},
 			Linker:    "cc",
-			PreLinkArgs: []string{"-no-pie"}, // WARNING: clang < 5.0 requires -nopie
+			LDFlags:   []string{"-no-pie"}, // WARNING: clang < 5.0 requires -nopie
 			Objcopy:   "objcopy",
 			GDB:       "gdb",
 			GDBCmds:   []string{"run"},

targets/arduino.json

@@ -2,14 +2,15 @@
 	"inherits": ["avr"],
 	"llvm-target": "avr-atmel-none",
 	"build-tags": ["arduino", "atmega328p", "atmega", "avr5"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostartfiles",
+		"-mmcu=atmega328p"
-		"-mmcu=avr5",
+	],
+	"ldflags": [
 		"-Wl,--defsym=_bootloader_size=512",
 		"-Wl,--defsym=_stack_size=512",
-		"-T", "src/device/avr/atmega328p.ld",
+		"-T", "src/device/avr/atmega328p.ld"
-		"-T", "targets/avr.ld",
+	],
-		"-Wl,--gc-sections",
+	"extra-files": [
 		"targets/avr.S",
 		"src/device/avr/atmega328p.s"
 	],

targets/arm.ld

@@ -1,4 +1,7 @@
 
+/* Unused, but here to silence a linker warning. */
+ENTRY(Reset_Handler)
+
 /* define output sections */
 SECTIONS
 {

targets/avr.json

@@ -1,5 +1,10 @@
 {
 	"build-tags": ["avr", "js", "wasm"],
+	"compiler": "avr-gcc",
 	"linker": "avr-gcc",
-	"objcopy": "avr-objcopy"
+	"objcopy": "avr-objcopy",
+	"ldflags": [
+		"-T", "targets/avr.ld",
+		"-Wl,--gc-sections"
+	]
 }

targets/bluepill.json

@@ -2,16 +2,14 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv7m-none-eabi",
 	"build-tags": ["bluepill", "stm32f103xx", "stm32"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostdlib",
+		"--target=armv7m-none-eabi",
-		"-nostartfiles",
+		"-Qunused-arguments"
-		"-mcpu=cortex-m3",
+	],
-		"-mthumb",
+	"ldflags": [
-		"-T", "targets/stm32.ld",
+		"-T", "targets/stm32.ld"
-		"-Wl,--gc-sections",
+	],
-		"-fno-exceptions", "-fno-unwind-tables",
+	"extra-files": [
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
 		"src/device/stm32/stm32f103xx.s"
 	],
 	"flash": "openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg -c 'program {hex} reset exit'"

targets/cortex-m.json

@@ -1,7 +1,18 @@
 {
 	"build-tags": ["tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
+	"compiler": "clang-7",
+	"linker": "arm-none-eabi-ld",
 	"rtlib": "compiler-rt",
+	"cflags": [
+		"-Oz",
+		"-mthumb",
+		"-fshort-enums",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections"
+	],
+	"ldflags": [
+		"--gc-sections"
+	],
 	"objcopy": "arm-none-eabi-objcopy",
 	"gdb": "arm-none-eabi-gdb"
 }

targets/cortex-m.s

@@ -26,7 +26,7 @@ Default_Handler:
     .set   \handler, Default_Handler
 .endm
 
-.section .isr_vector
+.section .isr_vector, "a", %progbits
 .global  __isr_vector
     // Interrupt vector as defined by Cortex-M, starting with the stack top.
     // On reset, SP is initialized with *0x0 and PC is loaded with *0x4, loading

targets/digispark.json

@@ -2,14 +2,15 @@
 	"inherits": ["avr"],
 	"llvm-target": "avr-atmel-none",
 	"build-tags": ["digispark", "attiny85", "attiny", "avr2", "avr25"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostartfiles",
+		"-mmcu=attiny85"
-		"-mmcu=attiny85",
+	],
+	"ldflags": [
 		"-Wl,--defsym=_bootloader_size=2180",
 		"-Wl,--defsym=_stack_size=128",
-		"-T", "src/device/avr/attiny85.ld",
+		"-T", "src/device/avr/attiny85.ld"
-		"-T", "targets/avr.ld",
+	],
-		"-Wl,--gc-sections",
+	"extra-files": [
 		"targets/avr.S",
 		"src/device/avr/attiny85.s"
 	],

targets/nrf51.json

@@ -2,18 +2,16 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv6m-none-eabi",
 	"build-tags": ["nrf51822", "nrf51", "nrf"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostdlib",
+		"--target=armv6m-none-eabi",
-		"-nostartfiles",
+		"-Qunused-arguments",
-		"-mcpu=cortex-m0",
-		"-mthumb",
-		"-T", "targets/nrf51.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
 		"-DNRF51",
-		"-Ilib/CMSIS/CMSIS/Include",
+		"-Ilib/CMSIS/CMSIS/Include"
+	],
+	"ldflags": [
+		"-T", "targets/nrf51.ld"
+	],
+	"extra-files": [
 		"lib/nrfx/mdk/system_nrf51.c",
 		"src/device/nrf/nrf51.s"
 	]

targets/nrf52.json

@@ -2,18 +2,16 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv7em-none-eabi",
 	"build-tags": ["nrf52", "nrf"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostdlib",
+		"--target=armv7em-none-eabi",
-		"-nostartfiles",
+		"-Qunused-arguments",
-		"-mcpu=cortex-m4",
-		"-mthumb",
-		"-T", "targets/nrf52.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
 		"-DNRF52832_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include",
+		"-Ilib/CMSIS/CMSIS/Include"
+	],
+	"ldflags": [
+		"-T", "targets/nrf52.ld"
+	],
+	"extra-files": [
 		"lib/nrfx/mdk/system_nrf52.c",
 		"src/device/nrf/nrf52.s"
 	]

targets/nrf52840.json

@@ -2,18 +2,16 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv7em-none-eabi",
 	"build-tags": ["nrf52840", "nrf"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostdlib",
+		"--target=armv7em-none-eabi",
-		"-nostartfiles",
+		"-Qunused-arguments",
-		"-mcpu=cortex-m4",
-		"-mthumb",
-		"-T", "targets/nrf52840.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
 		"-DNRF52840_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include",
+		"-Ilib/CMSIS/CMSIS/Include"
+	],
+	"ldflags": [
+		"-T", "targets/nrf52840.ld"
+	],
+	"extra-files": [
 		"lib/nrfx/mdk/system_nrf52840.c",
 		"src/device/nrf/nrf52840.s"
 	]

targets/qemu.json

@@ -2,16 +2,14 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv7m-none-eabi",
 	"build-tags": ["qemu", "lm3s6965"],
-	"pre-link-args": [
+	"cflags": [
-		"-nostdlib",
+		"--target=armv7m-none-eabi",
-		"-nostartfiles",
+		"-Qunused-arguments"
-		"-mcpu=cortex-m0",
+	],
-		"-mthumb",
+	"ldflags": [
-		"-T", "targets/lm3s6965.ld",
+		"-T", "targets/lm3s6965.ld"
-		"-Wl,--gc-sections",
+	],
-		"-fno-exceptions", "-fno-unwind-tables",
+	"extra-files": [
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
 		"targets/cortex-m.s"
 	],
 	"emulator": ["qemu-system-arm", "-machine", "lm3s6965evb", "-semihosting", "-nographic", "-kernel"]