WIP x509 on macOS

Running tests against an installed TinyGoRoot fails with:
```
=== CONT  TestBuild/WebAssembly/gc.go-boehm
    main_test.go:441: wasi-libc: did not find any files for pattern builder.filePattern{glob:"dlmalloc/src/dlmalloc.c", exclude:[]string(nil)}
```
because these files are not there, and are required with Boehm GC.

BUILDING.md

@@ -85,11 +85,17 @@ Try running TinyGo:
 
     ./build/tinygo help
 
-Also, make sure the `tinygo` binary really is statically linked. Check this
-using `ldd` (not to be confused with `lld`):
+Also, make sure the `tinygo` binary really is statically linked. The command to check for 
+dynamic dependencies differs depending on your operating system.
+
+On Linux, use `ldd` (not to be confused with `lld`):
 
     ldd ./build/tinygo
 
+On macOS, use otool -L:
+
+    otool -L ./build/tinygo
+
 The result should not contain libclang or libLLVM.
 
 ## Make a release tarball

GNUmakefile

@@ -187,7 +187,10 @@ fmt-check: ## Warn if any source needs reformatting
 	@unformatted=$$(gofmt -l $(FMT_PATHS)); [ -z "$$unformatted" ] && exit 0; echo "Unformatted:"; for fn in $$unformatted; do echo "  $$fn"; done; exit 1
 
 
-gen-device: gen-device-avr gen-device-esp gen-device-nrf gen-device-sam gen-device-sifive gen-device-kendryte gen-device-nxp gen-device-rp gen-device-renesas ## Generate microcontroller-specific sources
+gen-device: gen-device-avr gen-device-esp gen-device-nrf gen-device-sam gen-device-sifive gen-device-kendryte gen-device-nxp gen-device-rp ## Generate microcontroller-specific sources
+ifneq ($(RENESAS), 0)
+gen-device: gen-device-renesas
+endif
 ifneq ($(STM32), 0)
 gen-device: gen-device-stm32
 endif
@@ -837,6 +840,8 @@ ifneq ($(STM32), 0)
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=mksnanov3           examples/blinky1
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=stm32l0x1           examples/serial
+	@$(MD5SUM) test.hex
 endif
 	$(TINYGO) build -size short -o test.hex -target=atmega328pb         examples/blinkm
 	@$(MD5SUM) test.hex
@@ -907,7 +912,7 @@ endif
 	$(TINYGO) build -size short -o test.hex -target=hw-651              examples/machinetest
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=hw-651-s110v8       examples/machinetest
-	@$(MD5SUM) test.hex	
+	@$(MD5SUM) test.hex
 ifneq ($(WASM), 0)
 	$(TINYGO) build -size short -o wasm.wasm -target=wasm               examples/wasm/export
 	$(TINYGO) build -size short -o wasm.wasm -target=wasm               examples/wasm/main
@@ -958,6 +963,7 @@ build/release: tinygo gen-device $(if $(filter 1,$(USE_SYSTEM_BINARYEN)),,binary
 	@mkdir -p build/release/tinygo/lib/nrfx
 	@mkdir -p build/release/tinygo/lib/picolibc/newlib/libc
 	@mkdir -p build/release/tinygo/lib/picolibc/newlib/libm
+	@mkdir -p build/release/tinygo/lib/wasi-libc/dlmalloc
 	@mkdir -p build/release/tinygo/lib/wasi-libc/libc-bottom-half
 	@mkdir -p build/release/tinygo/lib/wasi-libc/libc-top-half/musl/arch
 	@mkdir -p build/release/tinygo/lib/wasi-libc/libc-top-half/musl/src
@@ -1029,6 +1035,7 @@ endif
 	@cp -rp lib/picolibc/newlib/libm/common      build/release/tinygo/lib/picolibc/newlib/libm
 	@cp -rp lib/picolibc/newlib/libm/math        build/release/tinygo/lib/picolibc/newlib/libm
 	@cp -rp lib/picolibc-stdio.c         build/release/tinygo/lib
+	@cp -rp lib/wasi-libc/dlmalloc/src                              build/release/tinygo/lib/wasi-libc/dlmalloc
 	@cp -rp lib/wasi-libc/libc-bottom-half/cloudlibc                build/release/tinygo/lib/wasi-libc/libc-bottom-half
 	@cp -rp lib/wasi-libc/libc-bottom-half/headers                  build/release/tinygo/lib/wasi-libc/libc-bottom-half
 	@cp -rp lib/wasi-libc/libc-bottom-half/sources                  build/release/tinygo/lib/wasi-libc/libc-bottom-half

compileopts/target.go

@@ -189,7 +189,7 @@ func LoadTarget(options *Options) (*TargetSpec, error) {
 		case "wasip2":
 			options.Target = "wasip2"
 		default:
-			return nil, errors.New("GOARCH=wasm but GOOS is not set correctly. Please set GOOS to wasm, wasip1, or wasip2.")
+			return nil, errors.New("GOARCH=wasm but GOOS is not set correctly. Please set GOOS to js, wasip1, or wasip2.")
 		}
 	}
 
@@ -369,7 +369,7 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 			return nil, fmt.Errorf("invalid GOMIPS=%s: must be hardfloat or softfloat", options.GOMIPS)
 		}
 	case "wasm":
-		return nil, fmt.Errorf("GOARCH=wasm but GOOS is unset. Please set GOOS to wasm, wasip1, or wasip2.")
+		return nil, fmt.Errorf("GOARCH=wasm but GOOS is unset. Please set GOOS to js, wasip1, or wasip2.")
 	default:
 		return nil, fmt.Errorf("unknown GOARCH=%s", options.GOARCH)
 	}
@@ -385,7 +385,7 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 			platformVersion = "11.0.0" // first macosx platform with arm64 support
 		}
 		llvmvendor = "apple"
-		spec.Scheduler = "tasks"
+		spec.Scheduler = "threads"
 		spec.Linker = "ld.lld"
 		spec.Libc = "darwin-libSystem"
 		// Use macosx* instead of darwin, otherwise darwin/arm64 will refer to
@@ -399,6 +399,7 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 		)
 		spec.ExtraFiles = append(spec.ExtraFiles,
 			"src/internal/futex/futex_darwin.c",
+			"src/internal/task/task_threads.c",
 			"src/runtime/os_darwin.c",
 			"src/runtime/runtime_unix.c",
 			"src/runtime/signal.c")

goenv/version.go

@@ -10,7 +10,7 @@ import (
 
 // Version of TinyGo.
 // Update this value before release of new version of software.
-const version = "0.38.0"
+const version = "0.39.0-dev"
 
 // Return TinyGo version, either in the form 0.30.0 or as a development version
 // (like 0.30.0-dev-abcd012).

loader/goroot.go

@@ -229,36 +229,33 @@ func needsSyscallPackage(buildTags []string) bool {
 // means use the TinyGo version.
 func pathsToOverride(goMinor int, needsSyscallPackage bool) map[string]bool {
 	paths := map[string]bool{
-		"":                            true,
-		"crypto/":                     true,
-		"crypto/rand/":                false,
-		"crypto/tls/":                 false,
-		"crypto/x509/":                true,
-		"crypto/x509/internal/":       true,
-		"crypto/x509/internal/macos/": false,
-		"device/":                     false,
-		"examples/":                   false,
-		"internal/":                   true,
-		"internal/abi/":               false,
-		"internal/binary/":            false,
-		"internal/bytealg/":           false,
-		"internal/cm/":                false,
-		"internal/futex/":             false,
-		"internal/fuzz/":              false,
-		"internal/reflectlite/":       false,
-		"internal/gclayout":           false,
-		"internal/task/":              false,
-		"internal/wasi/":              false,
-		"machine/":                    false,
-		"net/":                        true,
-		"net/http/":                   false,
-		"os/":                         true,
-		"reflect/":                    false,
-		"runtime/":                    false,
-		"sync/":                       true,
-		"testing/":                    true,
-		"tinygo/":                     false,
-		"unique/":                     false,
+		"":                      true,
+		"crypto/":               true,
+		"crypto/rand/":          false,
+		"crypto/tls/":           false,
+		"device/":               false,
+		"examples/":             false,
+		"internal/":             true,
+		"internal/abi/":         false,
+		"internal/binary/":      false,
+		"internal/bytealg/":     false,
+		"internal/cm/":          false,
+		"internal/futex/":       false,
+		"internal/fuzz/":        false,
+		"internal/reflectlite/": false,
+		"internal/gclayout":     false,
+		"internal/task/":        false,
+		"internal/wasi/":        false,
+		"machine/":              false,
+		"net/":                  true,
+		"net/http/":             false,
+		"os/":                   true,
+		"reflect/":              false,
+		"runtime/":              false,
+		"sync/":                 true,
+		"testing/":              true,
+		"tinygo/":               false,
+		"unique/":               false,
 	}
 
 	if goMinor >= 19 {

main_test.go

@@ -424,10 +424,12 @@ func optionsFromOSARCH(osarch string, sema chan struct{}) compileopts.Options {
 }
 
 func runTest(name string, options compileopts.Options, t *testing.T, cmdArgs, environmentVars []string) {
+	t.Helper()
 	runTestWithConfig(name, t, options, cmdArgs, environmentVars)
 }
 
 func runTestWithConfig(name string, t *testing.T, options compileopts.Options, cmdArgs, environmentVars []string) {
+	t.Helper()
 	// Get the expected output for this test.
 	// Note: not using filepath.Join as it strips the path separator at the end
 	// of the path.
@@ -876,6 +878,7 @@ func TestWasmExit(t *testing.T) {
 
 // Check whether the output of a test equals the expected output.
 func checkOutput(t *testing.T, filename string, actual []byte) {
+	t.Helper()
 	expectedOutput, err := os.ReadFile(filename)
 	if err != nil {
 		t.Fatal("could not read output file:", err)
@@ -884,6 +887,7 @@ func checkOutput(t *testing.T, filename string, actual []byte) {
 }
 
 func checkOutputData(t *testing.T, expectedOutput, actual []byte) {
+	t.Helper()
 	expectedOutput = bytes.ReplaceAll(expectedOutput, []byte("\r\n"), []byte("\n"))
 	actual = bytes.ReplaceAll(actual, []byte("\r\n"), []byte("\n"))
 

src/crypto/x509/internal/macos/macos.go

@@ -1,185 +0,0 @@
-package macos
-
-import (
-	"errors"
-	"time"
-)
-
-// Exported symbols copied from Big Go, but stripped of functionality.
-// Allows building of crypto/x509 on macOS.
-
-const (
-	ErrSecCertificateExpired = -67818
-	ErrSecHostNameMismatch   = -67602
-	ErrSecNotTrusted         = -67843
-)
-
-var ErrNoTrustSettings = errors.New("no trust settings found")
-var SecPolicyAppleSSL = StringToCFString("1.2.840.113635.100.1.3") // defined by POLICYMACRO
-var SecPolicyOid = StringToCFString("SecPolicyOid")
-var SecTrustSettingsPolicy = StringToCFString("kSecTrustSettingsPolicy")
-var SecTrustSettingsPolicyString = StringToCFString("kSecTrustSettingsPolicyString")
-var SecTrustSettingsResultKey = StringToCFString("kSecTrustSettingsResult")
-
-func CFArrayAppendValue(array CFRef, val CFRef) {}
-
-func CFArrayGetCount(array CFRef) int {
-	return 0
-}
-
-func CFDataGetBytePtr(data CFRef) uintptr {
-	return 0
-}
-
-func CFDataGetLength(data CFRef) int {
-	return 0
-}
-
-func CFDataToSlice(data CFRef) []byte {
-	return nil
-}
-
-func CFEqual(a, b CFRef) bool {
-	return false
-}
-
-func CFErrorGetCode(errRef CFRef) int {
-	return 0
-}
-
-func CFNumberGetValue(num CFRef) (int32, error) {
-	return 0, errors.New("not implemented")
-}
-
-func CFRelease(ref CFRef) {}
-
-func CFStringToString(ref CFRef) string {
-	return ""
-}
-
-func ReleaseCFArray(array CFRef) {}
-
-func SecCertificateCopyData(cert CFRef) ([]byte, error) {
-	return nil, errors.New("not implemented")
-}
-
-func SecTrustEvaluateWithError(trustObj CFRef) (int, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustGetCertificateCount(trustObj CFRef) int {
-	return 0
-}
-
-func SecTrustGetResult(trustObj CFRef, result CFRef) (CFRef, CFRef, error) {
-	return 0, 0, errors.New("not implemented")
-}
-
-func SecTrustSetVerifyDate(trustObj CFRef, dateRef CFRef) error {
-	return errors.New("not implemented")
-}
-
-type CFRef uintptr
-
-func BytesToCFData(b []byte) CFRef {
-	return 0
-}
-
-func CFArrayCreateMutable() CFRef {
-	return 0
-}
-
-func CFArrayGetValueAtIndex(array CFRef, index int) CFRef {
-	return 0
-}
-
-func CFDateCreate(seconds float64) CFRef {
-	return 0
-}
-
-func CFDictionaryGetValueIfPresent(dict CFRef, key CFString) (value CFRef, ok bool) {
-	return 0, false
-}
-
-func CFErrorCopyDescription(errRef CFRef) CFRef {
-	return 0
-}
-
-func CFStringCreateExternalRepresentation(strRef CFRef) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecCertificateCreateWithData(b []byte) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecPolicyCreateSSL(name string) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustCreateWithCertificates(certs CFRef, policies CFRef) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustEvaluate(trustObj CFRef) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustGetCertificateAtIndex(trustObj CFRef, i int) (CFRef, error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustSettingsCopyCertificates(domain SecTrustSettingsDomain) (certArray CFRef, err error) {
-	return 0, errors.New("not implemented")
-}
-
-func SecTrustSettingsCopyTrustSettings(cert CFRef, domain SecTrustSettingsDomain) (trustSettings CFRef, err error) {
-	return 0, errors.New("not implemented")
-}
-
-func TimeToCFDateRef(t time.Time) CFRef {
-	return 0
-}
-
-type CFString CFRef
-
-func StringToCFString(s string) CFString {
-	return 0
-}
-
-type OSStatus struct {
-	// Has unexported fields.
-}
-
-func (s OSStatus) Error() string
-
-type SecTrustResultType int32
-
-const (
-	SecTrustResultInvalid SecTrustResultType = iota
-	SecTrustResultProceed
-	SecTrustResultConfirm // deprecated
-	SecTrustResultDeny
-	SecTrustResultUnspecified
-	SecTrustResultRecoverableTrustFailure
-	SecTrustResultFatalTrustFailure
-	SecTrustResultOtherError
-)
-
-type SecTrustSettingsDomain int32
-
-const (
-	SecTrustSettingsDomainUser SecTrustSettingsDomain = iota
-	SecTrustSettingsDomainAdmin
-	SecTrustSettingsDomainSystem
-)
-
-type SecTrustSettingsResult int32
-
-const (
-	SecTrustSettingsResultInvalid SecTrustSettingsResult = iota
-	SecTrustSettingsResultTrustRoot
-	SecTrustSettingsResultTrustAsRoot
-	SecTrustSettingsResultDeny
-	SecTrustSettingsResultUnspecified
-)

src/internal/gclayout/gclayout.go

@@ -5,29 +5,20 @@ import "unsafe"
 // Internal constants for gc layout
 // See runtime/gc_precise.go
 
-var (
-	NoPtrs  unsafe.Pointer
-	Pointer unsafe.Pointer
-	String  unsafe.Pointer
-	Slice   unsafe.Pointer
+type Layout uintptr
+
+const (
+	// 16-bit int => bits = 4
+	// 32-bit int => bits = 5
+	// 64-bit int => bits = 6
+	sizeBits = 4 + unsafe.Sizeof(uintptr(0))/4
+
+	sizeShift = sizeBits + 1
+
+	NoPtrs  = Layout(uintptr(0b0<<sizeShift) | uintptr(0b1<<1) | uintptr(1))
+	Pointer = Layout(uintptr(0b1<<sizeShift) | uintptr(0b1<<1) | uintptr(1))
+	String  = Layout(uintptr(0b01<<sizeShift) | uintptr(0b10<<1) | uintptr(1))
+	Slice   = Layout(uintptr(0b001<<sizeShift) | uintptr(0b11<<1) | uintptr(1))
 )
 
-func init() {
-	var sizeBits uintptr
-
-	switch unsafe.Sizeof(uintptr(0)) {
-	case 8:
-		sizeBits = 6
-	case 4:
-		sizeBits = 5
-	case 2:
-		sizeBits = 4
-	}
-
-	var sizeShift = sizeBits + 1
-
-	NoPtrs = unsafe.Pointer(uintptr(0b0<<sizeShift) | uintptr(0b1<<1) | uintptr(1))
-	Pointer = unsafe.Pointer(uintptr(0b1<<sizeShift) | uintptr(0b1<<1) | uintptr(1))
-	String = unsafe.Pointer(uintptr(0b01<<sizeShift) | uintptr(0b10<<1) | uintptr(1))
-	Slice = unsafe.Pointer(uintptr(0b001<<sizeShift) | uintptr(0b11<<1) | uintptr(1))
-}
+func (l Layout) AsPtr() unsafe.Pointer { return unsafe.Pointer(l) }

src/internal/reflectlite/type.go

@@ -708,16 +708,16 @@ func (r *RawType) gcLayout() unsafe.Pointer {
 	kind := r.Kind()
 
 	if kind < String {
-		return gclayout.NoPtrs
+		return gclayout.NoPtrs.AsPtr()
 	}
 
 	switch kind {
 	case Pointer, UnsafePointer, Chan, Map:
-		return gclayout.Pointer
+		return gclayout.Pointer.AsPtr()
 	case String:
-		return gclayout.String
+		return gclayout.String.AsPtr()
 	case Slice:
-		return gclayout.Slice
+		return gclayout.Slice.AsPtr()
 	}
 
 	// Unknown (for now); let the conservative pointer scanning handle it

src/internal/task/darwin.go

@@ -0,0 +1,11 @@
+//go:build darwin
+
+package task
+
+import "unsafe"
+
+// MacOS uses a pointer so unsafe.Pointer should be fine:
+//
+//	typedef struct _opaque_pthread_t *__darwin_pthread_t;
+//	typedef __darwin_pthread_t pthread_t;
+type threadID unsafe.Pointer

src/internal/task/task_threads.c

@@ -2,16 +2,28 @@
 
 #define _GNU_SOURCE
 #include <pthread.h>
-#include <semaphore.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <unistd.h>
 
-// BDWGC also uses SIGRTMIN+6 on Linux, which seems like a reasonable choice.
 #ifdef __linux__
+#include <semaphore.h>
+
+// BDWGC also uses SIGRTMIN+6 on Linux, which seems like a reasonable choice.
 #define taskPauseSignal (SIGRTMIN + 6)
-#endif
+
+#elif __APPLE__
+#include <dispatch/dispatch.h>
+// SIGIO is for interrupt-driven I/O.
+// I don't think anybody should be using this nowadays, so I think we can
+// repurpose it as a signal for GC.
+// BDWGC uses a special way to pause/resume other threads on MacOS, which may be
+// better but needs more work. Using signal keeps the code similar between Linux
+// and MacOS.
+#define taskPauseSignal SIGIO
+
+#endif // __linux__, __APPLE__
 
 // Pointer to the current task.Task structure.
 // Ideally the entire task.Task structure would be a thread-local variable but
@@ -23,7 +35,11 @@ struct state_pass {
     void      *args;
     void      *task;
     uintptr_t *stackTop;
+    #if __APPLE__
+    dispatch_semaphore_t startlock;
+    #else
     sem_t     startlock;
+    #endif
 };
 
 // Handle the GC pause in Go.
@@ -41,8 +57,7 @@ void tinygo_task_init(void *mainTask, pthread_t *thread, int *numCPU, void *cont
     // Register the "GC pause" signal for the entire process.
     // Using pthread_kill, we can still send the signal to a specific thread.
     struct sigaction act = { 0 };
-    act.sa_flags = SA_SIGINFO;
-    act.sa_handler = &tinygo_task_gc_pause;
+    act.sa_handler = tinygo_task_gc_pause;
     sigaction(taskPauseSignal, &act, NULL);
 
     // Obtain the number of CPUs available on program start (for NumCPU).
@@ -69,7 +84,11 @@ static void* start_wrapper(void *arg) {
 
     // Notify the caller that the thread has successfully started and
     // initialized.
+    #if __APPLE__
+    dispatch_semaphore_signal(state->startlock);
+    #else
     sem_post(&state->startlock);
+    #endif
 
     // Run the goroutine function.
     start(args);
@@ -93,11 +112,19 @@ int tinygo_task_start(uintptr_t fn, void *args, void *task, pthread_t *thread, u
         .task      = task,
         .stackTop  = stackTop,
     };
+    #if __APPLE__
+    state.startlock = dispatch_semaphore_create(0);
+    #else
     sem_init(&state.startlock, 0, 0);
+    #endif
     int result = pthread_create(thread, NULL, &start_wrapper, &state);
 
     // Wait until the thread has been created and read all state_pass variables.
+    #if __APPLE__
+    dispatch_semaphore_wait(state.startlock, DISPATCH_TIME_FOREVER);
+    #else
     sem_wait(&state.startlock);
+    #endif
 
     return result;
 }

src/internal/task/task_threads.go

@@ -220,7 +220,7 @@ func gcScanGlobals()
 var stackScanLock PMutex
 
 //export tinygo_task_gc_pause
-func tingyo_task_gc_pause() {
+func tingyo_task_gc_pause(sig int32) {
 	// Wait until we get the signal to start scanning the stack.
 	Current().state.gcSem.Wait()
 

src/machine/board_atmega328p.go

@@ -27,8 +27,8 @@ const (
 	PC1 = portC + 1
 	PC2 = portC + 2
 	PC3 = portC + 3
-	PC4 = portC + 4
-	PC5 = portC + 5
+	PC4 = portC + 4 // peripherals: I2C0 SDA
+	PC5 = portC + 5 // peripherals: I2C0 SCL
 	PC6 = portC + 6
 	PC7 = portC + 7
 	PD0 = portD + 0

src/machine/board_atmega328pb.go

@@ -28,8 +28,8 @@ const (
 	PC1 = portC + 1
 	PC2 = portC + 2
 	PC3 = portC + 3
-	PC4 = portC + 4
-	PC5 = portC + 5
+	PC4 = portC + 4 // peripherals: I2C0 SDA
+	PC5 = portC + 5 // peripherals: I2C0 SCL
 	PC6 = portC + 6
 	PC7 = portC + 7
 	PD0 = portD + 0
@@ -40,8 +40,8 @@ const (
 	PD5 = portD + 5 // peripherals: Timer0 channel B
 	PD6 = portD + 6 // peripherals: Timer0 channel A
 	PD7 = portD + 7
-	PE0 = portE + 0
-	PE1 = portE + 1
+	PE0 = portE + 0 // peripherals: I2C1 SDA
+	PE1 = portE + 1 // peripherals: I2C1 SCL
 	PE2 = portE + 2
 	PE3 = portE + 3
 	PE4 = portE + 4

src/machine/board_atsamd21.go

@@ -7,32 +7,36 @@ func CPUFrequency() uint32 {
 	return 48000000
 }
 
+// Note that the below pins have a few I2C pins listed that according to the
+// datasheet don't support I2C yet they are used in practice on boards from
+// Adafruit and Arduino. See machine_atsamd21_simulator.go for details.
+
 // Hardware pins
 const (
-	PA00 Pin = 0 // peripherals: TCC2 channel 0
-	PA01 Pin = 1 // peripherals: TCC2 channel 1
+	PA00 Pin = 0 // peripherals: TCC2 channel 0, sercomI2CM1 SDA
+	PA01 Pin = 1 // peripherals: TCC2 channel 1, sercomI2CM1 SCL
 	PA02 Pin = 2
 	PA03 Pin = 3
 	PA04 Pin = 4  // peripherals: TCC0 channel 0
 	PA05 Pin = 5  // peripherals: TCC0 channel 1
 	PA06 Pin = 6  // peripherals: TCC1 channel 0
 	PA07 Pin = 7  // peripherals: TCC1 channel 1
-	PA08 Pin = 8  // peripherals: TCC0 channel 0, TCC1 channel 2
-	PA09 Pin = 9  // peripherals: TCC0 channel 1, TCC1 channel 3
+	PA08 Pin = 8  // peripherals: TCC0 channel 0, TCC1 channel 2, sercomI2CM0 SDA, sercomI2CM2 SDA
+	PA09 Pin = 9  // peripherals: TCC0 channel 1, TCC1 channel 3, sercomI2CM0 SCL, sercomI2CM2 SCL
 	PA10 Pin = 10 // peripherals: TCC1 channel 0, TCC0 channel 2
 	PA11 Pin = 11 // peripherals: TCC1 channel 1, TCC0 channel 3
-	PA12 Pin = 12 // peripherals: TCC2 channel 0, TCC0 channel 2
-	PA13 Pin = 13 // peripherals: TCC2 channel 1, TCC0 channel 3
+	PA12 Pin = 12 // peripherals: TCC2 channel 0, TCC0 channel 2, sercomI2CM2 SDA, sercomI2CM4 SDA
+	PA13 Pin = 13 // peripherals: TCC2 channel 1, TCC0 channel 3, sercomI2CM2 SCL, sercomI2CM4 SCL
 	PA14 Pin = 14 // peripherals: TCC0 channel 0
 	PA15 Pin = 15 // peripherals: TCC0 channel 1
-	PA16 Pin = 16 // peripherals: TCC2 channel 0, TCC0 channel 2
-	PA17 Pin = 17 // peripherals: TCC2 channel 1, TCC0 channel 3
+	PA16 Pin = 16 // peripherals: TCC2 channel 0, TCC0 channel 2, sercomI2CM1 SDA, sercomI2CM3 SDA
+	PA17 Pin = 17 // peripherals: TCC2 channel 1, TCC0 channel 3, sercomI2CM1 SCL, sercomI2CM3 SCL
 	PA18 Pin = 18 // peripherals: TCC0 channel 2
 	PA19 Pin = 19 // peripherals: TCC0 channel 3
 	PA20 Pin = 20 // peripherals: TCC0 channel 2
 	PA21 Pin = 21 // peripherals: TCC0 channel 3
-	PA22 Pin = 22 // peripherals: TCC0 channel 0
-	PA23 Pin = 23 // peripherals: TCC0 channel 1
+	PA22 Pin = 22 // peripherals: TCC0 channel 0, sercomI2CM3 SDA, sercomI2CM5 SDA
+	PA23 Pin = 23 // peripherals: TCC0 channel 1, sercomI2CM3 SCL, sercomI2CM5 SCL
 	PA24 Pin = 24 // peripherals: TCC1 channel 2
 	PA25 Pin = 25 // peripherals: TCC1 channel 3
 	PA26 Pin = 26
@@ -43,22 +47,22 @@ const (
 	PA31 Pin = 31 // peripherals: TCC1 channel 1
 	PB00 Pin = 32
 	PB01 Pin = 33
-	PB02 Pin = 34
-	PB03 Pin = 35
+	PB02 Pin = 34 // peripherals: sercomI2CM5 SDA
+	PB03 Pin = 35 // peripherals: sercomI2CM5 SCL
 	PB04 Pin = 36
 	PB05 Pin = 37
 	PB06 Pin = 38
 	PB07 Pin = 39
-	PB08 Pin = 40
-	PB09 Pin = 41
+	PB08 Pin = 40 // peripherals: sercomI2CM4 SDA
+	PB09 Pin = 41 // peripherals: sercomI2CM4 SCL
 	PB10 Pin = 42 // peripherals: TCC0 channel 0
 	PB11 Pin = 43 // peripherals: TCC0 channel 1
-	PB12 Pin = 44 // peripherals: TCC0 channel 2
-	PB13 Pin = 45 // peripherals: TCC0 channel 3
+	PB12 Pin = 44 // peripherals: TCC0 channel 2, sercomI2CM4 SDA
+	PB13 Pin = 45 // peripherals: TCC0 channel 3, sercomI2CM4 SCL
 	PB14 Pin = 46
 	PB15 Pin = 47
-	PB16 Pin = 48 // peripherals: TCC0 channel 0
-	PB17 Pin = 49 // peripherals: TCC0 channel 1
+	PB16 Pin = 48 // peripherals: TCC0 channel 0, sercomI2CM5 SDA
+	PB17 Pin = 49 // peripherals: TCC0 channel 1, sercomI2CM5 SCL
 	PB18 Pin = 50
 	PB19 Pin = 51
 	PB20 Pin = 52
@@ -71,6 +75,6 @@ const (
 	PB27 Pin = 59
 	PB28 Pin = 60
 	PB29 Pin = 61
-	PB30 Pin = 62 // peripherals: TCC0 channel 0, TCC1 channel 2
-	PB31 Pin = 63 // peripherals: TCC0 channel 1, TCC1 channel 3
+	PB30 Pin = 62 // peripherals: TCC0 channel 0, TCC1 channel 2, sercomI2CM5 SDA
+	PB31 Pin = 63 // peripherals: TCC0 channel 1, TCC1 channel 3, sercomI2CM5 SCL
 )

src/machine/board_pga2350.go

@@ -31,25 +31,24 @@ const (
 	GP27 = GPIO27
 	GP28 = GPIO28
 	GP29 = GPIO29
-	GP30 = GPIO30 // peripherals: PWM7 channel A
-	GP31 = GPIO31 // peripherals: PWM7 channel B
-	GP32 = GPIO32 // peripherals: PWM8 channel A
-	GP33 = GPIO33 // peripherals: PWM8 channel B
-	GP34 = GPIO34 // peripherals: PWM9 channel A
-	GP35 = GPIO35 // peripherals: PWM9 channel B
-	GP36 = GPIO36 // peripherals: PWM10 channel A
-	GP37 = GPIO37 // peripherals: PWM10 channel B
-	GP38 = GPIO38 // peripherals: PWM11 channel A
-	GP39 = GPIO39 // peripherals: PWM11 channel B
-	GP40 = GPIO40 // peripherals: PWM8 channel A
-	GP41 = GPIO41 // peripherals: PWM8 channel B
-	GP42 = GPIO42 // peripherals: PWM9 channel A
-	GP43 = GPIO43 // peripherals: PWM9 channel B
-	GP44 = GPIO44 // peripherals: PWM10 channel A
-	GP45 = GPIO45 // peripherals: PWM10 channel B
-	GP46 = GPIO46 // peripherals: PWM11 channel A
-	GP47 = GPIO47 // peripherals: PWM11 channel B
-
+	GP30 = GPIO30
+	GP31 = GPIO31
+	GP32 = GPIO32
+	GP33 = GPIO33
+	GP34 = GPIO34
+	GP35 = GPIO35
+	GP36 = GPIO36
+	GP37 = GPIO37
+	GP38 = GPIO38
+	GP39 = GPIO39
+	GP40 = GPIO40
+	GP41 = GPIO41
+	GP42 = GPIO42
+	GP43 = GPIO43
+	GP44 = GPIO44
+	GP45 = GPIO45
+	GP46 = GPIO46
+	GP47 = GPIO47
 )
 
 var DefaultUART = UART0

src/machine/board_stm32l0x1.go

@@ -0,0 +1,18 @@
+//go:build stm32l0x1 && !nucleol031k6
+
+// This file is for the bare STM32L0x1 (not for any specific board that is based
+// on the STM32L0x1).
+
+package machine
+
+const (
+	I2C0_SCL_PIN = NoPin
+	I2C0_SDA_PIN = NoPin
+
+	UART_TX_PIN = NoPin
+	UART_RX_PIN = NoPin
+
+	SPI0_SDI_PIN = NoPin
+	SPI0_SDO_PIN = NoPin
+	SPI0_SCK_PIN = NoPin
+)

src/machine/board_teensy41.go

@@ -279,7 +279,7 @@ var (
 // #===========#==========#===============#=================-=========#
 // |   SPI1    |  LPSPI4  | PLL2(132 MHz) | D12/D11/D13/D10 : 3/3/3/3 |
 // |   SPI2    |  LPSPI3  | PLL2(132 MHz) |  D1/D26/D27/D0  : 7/2/2/7 |
-// |   SPI3    |  LPSPI1  | PLL2(132 MHz) | D34/D35/D37/D36 : 4/4/4/4 |
+// |   SPI3    |  LPSPI1  | PLL2(132 MHz) | D42/D43/D45/D44 : 4/4/4/4 |
 // #===========#==========#===============#=================-=========#
 const (
 	SPI1_SDI_PIN = D12
@@ -292,10 +292,52 @@ const (
 	SPI2_SCK_PIN = D27
 	SPI2_CS_PIN  = D0
 
-	SPI3_SDI_PIN = D34
-	SPI3_SDO_PIN = D35
-	SPI3_SCK_PIN = D37
-	SPI3_CS_PIN  = D36
+	SPI3_SDI_PIN = D42
+	SPI3_SDO_PIN = D43
+	SPI3_SCK_PIN = D45
+	SPI3_CS_PIN  = D44
+)
+
+var (
+	SPI0 = SPI1 // SPI0 is an alias of SPI1 (LPSPI4)
+	SPI1 = &SPI{
+		Bus: nxp.LPSPI4,
+		muxSDI: muxSelect{ // D12 (PB1 [B0_01])
+			mux: nxp.IOMUXC_LPSPI4_SDI_SELECT_INPUT_DAISY_GPIO_B0_01_ALT3,
+			sel: &nxp.IOMUXC.LPSPI4_SDI_SELECT_INPUT,
+		},
+		muxSDO: muxSelect{ // D11 (PB2 [B0_02])
+			mux: nxp.IOMUXC_LPSPI4_SDO_SELECT_INPUT_DAISY_GPIO_B0_02_ALT3,
+			sel: &nxp.IOMUXC.LPSPI4_SDO_SELECT_INPUT,
+		},
+		muxSCK: muxSelect{ // D13 (PB3 [B0_03])
+			mux: nxp.IOMUXC_LPSPI4_SCK_SELECT_INPUT_DAISY_GPIO_B0_03_ALT3,
+			sel: &nxp.IOMUXC.LPSPI4_SCK_SELECT_INPUT,
+		},
+		muxCS: muxSelect{ // D10 (PB0 [B0_00])
+			mux: nxp.IOMUXC_LPSPI4_PCS0_SELECT_INPUT_DAISY_GPIO_B0_00_ALT3,
+			sel: &nxp.IOMUXC.LPSPI4_PCS0_SELECT_INPUT,
+		},
+	}
+	SPI2 = &SPI{
+		Bus: nxp.LPSPI3,
+		muxSDI: muxSelect{ // D1 (PA2 [AD_B0_02])
+			mux: nxp.IOMUXC_LPSPI3_SDI_SELECT_INPUT_DAISY_GPIO_AD_B0_02_ALT7,
+			sel: &nxp.IOMUXC.LPSPI3_SDI_SELECT_INPUT,
+		},
+		muxSDO: muxSelect{ // D26 (PA30 [AD_B1_14])
+			mux: nxp.IOMUXC_LPSPI3_SDO_SELECT_INPUT_DAISY_GPIO_AD_B1_14_ALT2,
+			sel: &nxp.IOMUXC.LPSPI3_SDO_SELECT_INPUT,
+		},
+		muxSCK: muxSelect{ // D27 (PA31 [AD_B1_15])
+			mux: nxp.IOMUXC_LPSPI3_SCK_SELECT_INPUT_DAISY_GPIO_AD_B1_15,
+			sel: &nxp.IOMUXC.LPSPI3_SCK_SELECT_INPUT,
+		},
+		muxCS: muxSelect{ // D0 (PA3 [AD_B0_03])
+			mux: nxp.IOMUXC_LPSPI3_PCS0_SELECT_INPUT_DAISY_GPIO_AD_B0_03_ALT7,
+			sel: &nxp.IOMUXC.LPSPI3_PCS0_SELECT_INPUT,
+		},
+	}
 )
 
 // #====================================================#
@@ -317,3 +359,49 @@ const (
 	I2C3_SDA_PIN = D25
 	I2C3_SCL_PIN = D24
 )
+
+var (
+	I2C0  = I2C1 // I2C0 is an alias for I2C1 (LPI2C1)
+	I2C1  = &_I2C1
+	_I2C1 = I2C{
+		Bus: nxp.LPI2C1,
+		sda: I2C1_SDA_PIN, // D18 (PA17 [AD_B1_01])
+		scl: I2C1_SCL_PIN, // D19 (PA16 [AD_B1_00])
+		muxSDA: muxSelect{
+			mux: nxp.IOMUXC_LPI2C1_SDA_SELECT_INPUT_DAISY_GPIO_AD_B1_01_ALT3,
+			sel: &nxp.IOMUXC.LPI2C1_SDA_SELECT_INPUT,
+		},
+		muxSCL: muxSelect{
+			mux: nxp.IOMUXC_LPI2C1_SCL_SELECT_INPUT_DAISY_GPIO_AD_B1_00_ALT3,
+			sel: &nxp.IOMUXC.LPI2C1_SCL_SELECT_INPUT,
+		},
+	}
+	I2C2  = &_I2C2
+	_I2C2 = I2C{
+		Bus: nxp.LPI2C3,
+		sda: I2C2_SDA_PIN, // D17 (PA22 [AD_B1_06])
+		scl: I2C2_SCL_PIN, // D16 (PA23 [AD_B1_07])
+		muxSDA: muxSelect{
+			mux: nxp.IOMUXC_LPI2C3_SDA_SELECT_INPUT_DAISY_GPIO_AD_B1_06_ALT1,
+			sel: &nxp.IOMUXC.LPI2C3_SDA_SELECT_INPUT,
+		},
+		muxSCL: muxSelect{
+			mux: nxp.IOMUXC_LPI2C3_SCL_SELECT_INPUT_DAISY_GPIO_AD_B1_07_ALT1,
+			sel: &nxp.IOMUXC.LPI2C3_SCL_SELECT_INPUT,
+		},
+	}
+	I2C3  = &_I2C3
+	_I2C3 = I2C{
+		Bus: nxp.LPI2C4,
+		sda: I2C3_SDA_PIN, // D25 (PA13 [AD_B0_13])
+		scl: I2C3_SCL_PIN, // D24 (PA12 [AD_B0_12])
+		muxSDA: muxSelect{
+			mux: nxp.IOMUXC_LPI2C4_SDA_SELECT_INPUT_DAISY_GPIO_AD_B0_13_ALT0,
+			sel: &nxp.IOMUXC.LPI2C4_SDA_SELECT_INPUT,
+		},
+		muxSCL: muxSelect{
+			mux: nxp.IOMUXC_LPI2C4_SCL_SELECT_INPUT_DAISY_GPIO_AD_B0_12_ALT0,
+			sel: &nxp.IOMUXC.LPI2C4_SCL_SELECT_INPUT,
+		},
+	}
+)

src/machine/i2c.go

@@ -26,17 +26,20 @@ const (
 )
 
 var (
-	errI2CWriteTimeout       = errors.New("I2C timeout during write")
-	errI2CReadTimeout        = errors.New("I2C timeout during read")
-	errI2CBusReadyTimeout    = errors.New("I2C timeout on bus ready")
-	errI2CSignalStartTimeout = errors.New("I2C timeout on signal start")
-	errI2CSignalReadTimeout  = errors.New("I2C timeout on signal read")
-	errI2CSignalStopTimeout  = errors.New("I2C timeout on signal stop")
-	errI2CAckExpected        = errors.New("I2C error: expected ACK not NACK")
-	errI2CBusError           = errors.New("I2C bus error")
-	errI2COverflow           = errors.New("I2C receive buffer overflow")
-	errI2COverread           = errors.New("I2C transmit buffer overflow")
-	errI2CNotImplemented     = errors.New("I2C operation not yet implemented")
+	errI2CWriteTimeout       = errors.New("i2c: timeout during write")
+	errI2CReadTimeout        = errors.New("i2c: timeout during read")
+	errI2CBusReadyTimeout    = errors.New("i2c: timeout on bus ready")
+	errI2CSignalStartTimeout = errors.New("i2c: timeout on signal start")
+	errI2CSignalReadTimeout  = errors.New("i2c: timeout on signal read")
+	errI2CSignalStopTimeout  = errors.New("i2c: timeout on signal stop")
+	errI2CAckExpected        = errors.New("i2c: error: expected ACK not NACK")
+	errI2CBusError           = errors.New("i2c: bus error")
+	errI2COverflow           = errors.New("i2c: receive buffer overflow")
+	errI2COverread           = errors.New("i2c: transmit buffer overflow")
+	errI2CNotImplemented     = errors.New("i2c: operation not yet implemented")
+	errI2CNoDevices          = errors.New("i2c: bus has no devices")                         // simulator only
+	errI2CMultipleDevices    = errors.New("i2c: bus has address conflict")                   // simulator only
+	errI2CWrongAddress       = errors.New("i2c: bus has devices but none with this address") // simulator only
 )
 
 // I2CTargetEvent reflects events on the I2C bus

src/machine/machine_atmega1280.go

@@ -49,8 +49,8 @@ const (
 	PC5 = portC + 5
 	PC6 = portC + 6
 	PC7 = portC + 7
-	PD0 = portD + 0
-	PD1 = portD + 1
+	PD0 = portD + 0 // peripherals: I2C0 SCL
+	PD1 = portD + 1 // peripherals: I2C0 SDA
 	PD2 = portD + 2
 	PD3 = portD + 3
 	PD7 = portD + 7

src/machine/machine_atmega328p_simulator.go

@@ -0,0 +1,5 @@
+//go:build !baremetal && (arduino || arduino_nano)
+
+package machine
+
+var I2C0 = &I2C{Bus: 0, PinsSDA: []Pin{PC4}, PinsSCL: []Pin{PC5}}

src/machine/machine_atsamd21_simulator.go

@@ -43,3 +43,21 @@ var TCC2 = &timerType{
 		{PA01, PA13, PA17}, // channel 1
 	},
 }
+
+var (
+	// According to the datasheet, only some pins have I2C support. However it
+	// looks like many boards just use any SERCOM I2C instance, even if the
+	// datasheet says those don't support I2C. I guess they do work in practice,
+	// then.
+	// These are:
+	//   * PA00/PA01 for the Adafruit Circuit Playground Express (I2C1, SERCOM1).
+	//   * PB02/PB03 for the Adafruit Circuit Playground Express (I2C0, SERCOM5).
+	//   * PB08/PB09 for the Arduino Nano 33 IoT (I2C0, SERCOM4).
+	// https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Atmel-42181-SAM-D21_Datasheet.pdf
+	sercomI2CM0 = &I2C{Bus: 0, PinsSDA: []Pin{PA08}, PinsSCL: []Pin{PA09}}
+	sercomI2CM1 = &I2C{Bus: 1, PinsSDA: []Pin{PA00, PA16}, PinsSCL: []Pin{PA01, PA17}}
+	sercomI2CM2 = &I2C{Bus: 2, PinsSDA: []Pin{PA08, PA12}, PinsSCL: []Pin{PA09, PA13}}
+	sercomI2CM3 = &I2C{Bus: 3, PinsSDA: []Pin{PA16, PA22}, PinsSCL: []Pin{PA17, PA23}}
+	sercomI2CM4 = &I2C{Bus: 4, PinsSDA: []Pin{PA12, PB08, PB12}, PinsSCL: []Pin{PA13, PB09, PB13}}
+	sercomI2CM5 = &I2C{Bus: 5, PinsSDA: []Pin{PA22, PB02, PB16, PB30}, PinsSCL: []Pin{PA23, PB03, PB17, PB31}}
+)

src/machine/machine_atsamd51.go

@@ -81,22 +81,22 @@ const (
 	PA05 Pin = 5
 	PA06 Pin = 6
 	PA07 Pin = 7
-	PA08 Pin = 8  // peripherals: TCC0 channel 0, TCC1 channel 4
-	PA09 Pin = 9  // peripherals: TCC0 channel 1, TCC1 channel 5
+	PA08 Pin = 8  // peripherals: TCC0 channel 0, TCC1 channel 4, sercomI2CM0 SDA, sercomI2CM2 SDA
+	PA09 Pin = 9  // peripherals: TCC0 channel 1, TCC1 channel 5, sercomI2CM0 SCL, sercomI2CM2 SCL
 	PA10 Pin = 10 // peripherals: TCC0 channel 2, TCC1 channel 6
 	PA11 Pin = 11 // peripherals: TCC0 channel 3, TCC1 channel 7
-	PA12 Pin = 12 // peripherals: TCC0 channel 6, TCC1 channel 2
-	PA13 Pin = 13 // peripherals: TCC0 channel 7, TCC1 channel 3
+	PA12 Pin = 12 // peripherals: TCC0 channel 6, TCC1 channel 2, sercomI2CM2 SDA, sercomI2CM4 SDA
+	PA13 Pin = 13 // peripherals: TCC0 channel 7, TCC1 channel 3, sercomI2CM2 SCL, sercomI2CM4 SCL
 	PA14 Pin = 14 // peripherals: TCC2 channel 0, TCC1 channel 2
 	PA15 Pin = 15 // peripherals: TCC2 channel 1, TCC1 channel 3
-	PA16 Pin = 16 // peripherals: TCC1 channel 0, TCC0 channel 4
-	PA17 Pin = 17 // peripherals: TCC1 channel 1, TCC0 channel 5
+	PA16 Pin = 16 // peripherals: TCC1 channel 0, TCC0 channel 4, sercomI2CM1 SDA, sercomI2CM3 SDA
+	PA17 Pin = 17 // peripherals: TCC1 channel 1, TCC0 channel 5, sercomI2CM1 SCL, sercomI2CM3 SCL
 	PA18 Pin = 18 // peripherals: TCC1 channel 2, TCC0 channel 6
 	PA19 Pin = 19 // peripherals: TCC1 channel 3, TCC0 channel 7
 	PA20 Pin = 20 // peripherals: TCC1 channel 4, TCC0 channel 0
 	PA21 Pin = 21 // peripherals: TCC1 channel 5, TCC0 channel 1
-	PA22 Pin = 22 // peripherals: TCC1 channel 6, TCC0 channel 2
-	PA23 Pin = 23 // peripherals: TCC1 channel 7, TCC0 channel 3
+	PA22 Pin = 22 // peripherals: TCC1 channel 6, TCC0 channel 2, sercomI2CM3 SDA, sercomI2CM5 SDA
+	PA23 Pin = 23 // peripherals: TCC1 channel 7, TCC0 channel 3, sercomI2CM3 SCL, sercomI2CM5 SCL
 	PA24 Pin = 24 // peripherals: TCC2 channel 2
 	PA25 Pin = 25 // peripherals: TCC2 channel 3
 	PA26 Pin = 26
@@ -177,8 +177,8 @@ const (
 	PD05 Pin = 101
 	PD06 Pin = 102
 	PD07 Pin = 103
-	PD08 Pin = 104 // peripherals: TCC0 channel 1
-	PD09 Pin = 105 // peripherals: TCC0 channel 2
+	PD08 Pin = 104 // peripherals: TCC0 channel 1, sercomI2CM6 SDA, sercomI2CM7 SDA
+	PD09 Pin = 105 // peripherals: TCC0 channel 2, sercomI2CM6 SCL, sercomI2CM7 SCL
 	PD10 Pin = 106 // peripherals: TCC0 channel 3
 	PD11 Pin = 107 // peripherals: TCC0 channel 4
 	PD12 Pin = 108 // peripherals: TCC0 channel 5

src/machine/machine_fe310_simulator.go

@@ -0,0 +1,5 @@
+//go:build !baremetal && hifive1b
+
+package machine
+
+var I2C0 = &I2C{Bus: 0, PinsSDA: []Pin{P12}, PinsSCL: []Pin{P13}}

src/machine/machine_generic.go

@@ -4,6 +4,8 @@ package machine
 
 import (
 	"crypto/rand"
+	"errors"
+	"slices"
 )
 
 // Dummy machine package that calls out to external functions.
@@ -227,7 +229,9 @@ func adcRead(pin Pin) uint16
 
 // I2C is a generic implementation of the Inter-IC communication protocol.
 type I2C struct {
-	Bus uint8
+	Bus     uint8
+	PinsSCL []Pin
+	PinsSDA []Pin
 }
 
 // I2CConfig is used to store config info for I2C.
@@ -239,7 +243,21 @@ type I2CConfig struct {
 
 // Configure is intended to setup the I2C interface.
 func (i2c *I2C) Configure(config I2CConfig) error {
-	i2cConfigure(i2c.Bus, config.SCL, config.SDA)
+	if i2c.PinsSCL != nil {
+		matchSCL := slices.Index(i2c.PinsSCL, config.SCL) >= 0
+		matchSDA := slices.Index(i2c.PinsSDA, config.SDA) >= 0
+		if !matchSCL && !matchSDA {
+			return errors.New("i2c: SCL and SDA pins are incorrect for this I2C instance")
+		} else if !matchSCL {
+			return errors.New("i2c: SCL pin is incorrect for this I2C instance")
+		} else if !matchSDA {
+			return errors.New("i2c: SDA pin is incorrect for this I2C instance")
+		}
+	}
+	if config.Frequency == 0 {
+		config.Frequency = 100 * KHz
+	}
+	i2cConfigure(i2c.Bus, config.SCL, config.SDA, config.Frequency)
 	return nil
 }
 
@@ -261,19 +279,29 @@ func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 		rptr = &r[0]
 		rlen = len(r)
 	}
-	i2cTransfer(i2c.Bus, wptr, wlen, rptr, rlen)
-	// TODO: do something with the returned error code.
-	return nil
+	errCode := i2cTransfer(i2c.Bus, addr, wptr, wlen, rptr, rlen)
+	switch errCode {
+	case 0:
+		return nil
+	case 1:
+		return errI2CNoDevices
+	case 2:
+		return errI2CMultipleDevices
+	case 3:
+		return errI2CWrongAddress
+	default:
+		return errI2CBusError // unknown error code
+	}
 }
 
 //export __tinygo_i2c_configure
-func i2cConfigure(bus uint8, scl Pin, sda Pin)
+func i2cConfigure(bus uint8, scl Pin, sda Pin, frequency uint32)
 
 //export __tinygo_i2c_set_baud_rate
 func i2cSetBaudRate(bus uint8, br uint32)
 
 //export __tinygo_i2c_transfer
-func i2cTransfer(bus uint8, w *byte, wlen int, r *byte, rlen int) int
+func i2cTransfer(bus uint8, addr uint16, w *byte, wlen int, r *byte, rlen int) int
 
 type UART struct {
 	Bus uint8
@@ -336,15 +364,6 @@ var (
 	sercomUSART4 = UART{4}
 	sercomUSART5 = UART{5}
 
-	sercomI2CM0 = &I2C{0}
-	sercomI2CM1 = &I2C{1}
-	sercomI2CM2 = &I2C{2}
-	sercomI2CM3 = &I2C{3}
-	sercomI2CM4 = &I2C{4}
-	sercomI2CM5 = &I2C{5}
-	sercomI2CM6 = &I2C{6}
-	sercomI2CM7 = &I2C{7}
-
 	sercomSPIM0 = &SPI{0}
 	sercomSPIM1 = &SPI{1}
 	sercomSPIM2 = &SPI{2}

src/machine/machine_generic_peripherals.go

@@ -10,5 +10,4 @@ var (
 	UART1 = hardwareUART1
 	SPI0  = &SPI{0}
 	SPI1  = &SPI{1}
-	I2C0  = &I2C{0}
 )

src/machine/machine_nrf51_simulator.go

@@ -0,0 +1,6 @@
+//go:build !baremetal && (microbit || pca10031 || hw_651)
+
+package machine
+
+var I2C0 = &I2C{Bus: 0}
+var I2C1 = &I2C{Bus: 1}

src/machine/machine_nrf52840_simulator.go

@@ -58,3 +58,6 @@ var PWM3 = &timerType{
 		nil, // channel 3
 	},
 }
+
+var I2C0 = &I2C{Bus: 0}
+var I2C1 = &I2C{Bus: 1}

src/machine/machine_rp2040_simulator.go

@@ -94,3 +94,15 @@ var PWM7 = &timerType{
 		{GPIO15}, // channel B (1)
 	},
 }
+
+var I2C0 = &I2C{
+	Bus:     0,
+	PinsSCL: []Pin{GPIO1, GPIO5, GPIO9, GPIO13, GPIO17, GPIO21},
+	PinsSDA: []Pin{GPIO0, GPIO4, GPIO8, GPIO12, GPIO16, GPIO20},
+}
+
+var I2C1 = &I2C{
+	Bus:     0,
+	PinsSCL: []Pin{GPIO3, GPIO7, GPIO11, GPIO15, GPIO19, GPIO27},
+	PinsSDA: []Pin{GPIO2, GPIO6, GPIO10, GPIO14, GPIO18, GPIO26},
+}

src/machine/machine_rp2_2350.go

@@ -150,6 +150,8 @@ func (p Pin) Configure(config PinConfig) {
 	case PinAnalog:
 		p.setFunc(fnNULL)
 		p.pulloff()
+		// Disable digital input.
+		p.padCtrl().ClearBits(rp.PADS_BANK0_GPIO0_IE)
 	case PinUART:
 		p.setFunc(fnUART)
 	case PinPWM:

src/machine/machine_rp2_2350b.go

@@ -5,24 +5,24 @@ package machine
 // RP2350B has additional pins.
 
 const (
-	GPIO30 Pin = 30 // peripherals: PWM7 channel A
-	GPIO31 Pin = 31 // peripherals: PWM7 channel B
-	GPIO32 Pin = 32 // peripherals: PWM8 channel A
-	GPIO33 Pin = 33 // peripherals: PWM8 channel B
-	GPIO34 Pin = 34 // peripherals: PWM9 channel A
-	GPIO35 Pin = 35 // peripherals: PWM9 channel B
-	GPIO36 Pin = 36 // peripherals: PWM10 channel A
-	GPIO37 Pin = 37 // peripherals: PWM10 channel B
-	GPIO38 Pin = 38 // peripherals: PWM11 channel A
-	GPIO39 Pin = 39 // peripherals: PWM11 channel B
-	GPIO40 Pin = 40 // peripherals: PWM8 channel A
-	GPIO41 Pin = 41 // peripherals: PWM8 channel B
-	GPIO42 Pin = 42 // peripherals: PWM9 channel A
-	GPIO43 Pin = 43 // peripherals: PWM9 channel B
-	GPIO44 Pin = 44 // peripherals: PWM10 channel A
-	GPIO45 Pin = 45 // peripherals: PWM10 channel B
-	GPIO46 Pin = 46 // peripherals: PWM11 channel A
-	GPIO47 Pin = 47 // peripherals: PWM11 channel B
+	GPIO30 Pin = 30 // peripherals: PWM7 channel A, I2C1 SDA
+	GPIO31 Pin = 31 // peripherals: PWM7 channel B, I2C1 SCL
+	GPIO32 Pin = 32 // peripherals: PWM8 channel A, I2C0 SDA
+	GPIO33 Pin = 33 // peripherals: PWM8 channel B, I2C0 SCL
+	GPIO34 Pin = 34 // peripherals: PWM9 channel A, I2C1 SDA
+	GPIO35 Pin = 35 // peripherals: PWM9 channel B, I2C1 SCL
+	GPIO36 Pin = 36 // peripherals: PWM10 channel A, I2C0 SDA
+	GPIO37 Pin = 37 // peripherals: PWM10 channel B, I2C0 SCL
+	GPIO38 Pin = 38 // peripherals: PWM11 channel A, I2C1 SDA
+	GPIO39 Pin = 39 // peripherals: PWM11 channel B, I2C1 SCL
+	GPIO40 Pin = 40 // peripherals: PWM8 channel A, I2C0 SDA
+	GPIO41 Pin = 41 // peripherals: PWM8 channel B, I2C0 SCL
+	GPIO42 Pin = 42 // peripherals: PWM9 channel A, I2C1 SDA
+	GPIO43 Pin = 43 // peripherals: PWM9 channel B, I2C1 SCL
+	GPIO44 Pin = 44 // peripherals: PWM10 channel A, I2C0 SDA
+	GPIO45 Pin = 45 // peripherals: PWM10 channel B, I2C0 SCL
+	GPIO46 Pin = 46 // peripherals: PWM11 channel A, I2C1 SDA
+	GPIO47 Pin = 47 // peripherals: PWM11 channel B, I2C1 SCL
 )
 
 // Analog pins on 2350b.

src/machine/machine_rp2_adc.go

@@ -73,14 +73,15 @@ func (c ADCChannel) Configure(config ADCConfig) error {
 func (c ADCChannel) getOnce() uint16 {
 	// Make it safe to sample multiple ADC channels in separate go routines.
 	adcLock.Lock()
-	rp.ADC.CS.ReplaceBits(uint32(c), 0b111, rp.ADC_CS_AINSEL_Pos)
+	rp.ADC.CS.ReplaceBits(uint32(c)<<rp.ADC_CS_AINSEL_Pos, rp.ADC_CS_AINSEL_Msk, 0)
 	rp.ADC.CS.SetBits(rp.ADC_CS_START_ONCE)
 
 	waitForReady()
+	v := rp.ADC.RESULT.Get()
 	adcLock.Unlock()
 
 	// rp2040 is a 12-bit ADC, scale raw reading to 16-bits.
-	return uint16(rp.ADC.RESULT.Get()) << 4
+	return uint16(v) << 4
 }
 
 // getVoltage does a one-shot sample and returns a millivolts reading.

src/machine/machine_rp2_pins.go

@@ -4,34 +4,34 @@ package machine
 
 const (
 	// GPIO pins
-	GPIO0  Pin = 0  // peripherals: PWM0 channel A
-	GPIO1  Pin = 1  // peripherals: PWM0 channel B
-	GPIO2  Pin = 2  // peripherals: PWM1 channel A
-	GPIO3  Pin = 3  // peripherals: PWM1 channel B
-	GPIO4  Pin = 4  // peripherals: PWM2 channel A
-	GPIO5  Pin = 5  // peripherals: PWM2 channel B
-	GPIO6  Pin = 6  // peripherals: PWM3 channel A
-	GPIO7  Pin = 7  // peripherals: PWM3 channel B
-	GPIO8  Pin = 8  // peripherals: PWM4 channel A
-	GPIO9  Pin = 9  // peripherals: PWM4 channel B
-	GPIO10 Pin = 10 // peripherals: PWM5 channel A
-	GPIO11 Pin = 11 // peripherals: PWM5 channel B
-	GPIO12 Pin = 12 // peripherals: PWM6 channel A
-	GPIO13 Pin = 13 // peripherals: PWM6 channel B
-	GPIO14 Pin = 14 // peripherals: PWM7 channel A
-	GPIO15 Pin = 15 // peripherals: PWM7 channel B
-	GPIO16 Pin = 16 // peripherals: PWM0 channel A
-	GPIO17 Pin = 17 // peripherals: PWM0 channel B
-	GPIO18 Pin = 18 // peripherals: PWM1 channel A
-	GPIO19 Pin = 19 // peripherals: PWM1 channel B
-	GPIO20 Pin = 20 // peripherals: PWM2 channel A
-	GPIO21 Pin = 21 // peripherals: PWM2 channel B
+	GPIO0  Pin = 0  // peripherals: PWM0 channel A, I2C0 SDA
+	GPIO1  Pin = 1  // peripherals: PWM0 channel B, I2C0 SCL
+	GPIO2  Pin = 2  // peripherals: PWM1 channel A, I2C1 SDA
+	GPIO3  Pin = 3  // peripherals: PWM1 channel B, I2C1 SCL
+	GPIO4  Pin = 4  // peripherals: PWM2 channel A, I2C0 SDA
+	GPIO5  Pin = 5  // peripherals: PWM2 channel B, I2C0 SCL
+	GPIO6  Pin = 6  // peripherals: PWM3 channel A, I2C1 SDA
+	GPIO7  Pin = 7  // peripherals: PWM3 channel B, I2C1 SCL
+	GPIO8  Pin = 8  // peripherals: PWM4 channel A, I2C0 SDA
+	GPIO9  Pin = 9  // peripherals: PWM4 channel B, I2C0 SCL
+	GPIO10 Pin = 10 // peripherals: PWM5 channel A, I2C1 SDA
+	GPIO11 Pin = 11 // peripherals: PWM5 channel B, I2C1 SCL
+	GPIO12 Pin = 12 // peripherals: PWM6 channel A, I2C0 SDA
+	GPIO13 Pin = 13 // peripherals: PWM6 channel B, I2C0 SCL
+	GPIO14 Pin = 14 // peripherals: PWM7 channel A, I2C1 SDA
+	GPIO15 Pin = 15 // peripherals: PWM7 channel B, I2C1 SCL
+	GPIO16 Pin = 16 // peripherals: PWM0 channel A, I2C0 SDA
+	GPIO17 Pin = 17 // peripherals: PWM0 channel B, I2C0 SCL
+	GPIO18 Pin = 18 // peripherals: PWM1 channel A, I2C1 SDA
+	GPIO19 Pin = 19 // peripherals: PWM1 channel B, I2C1 SCL
+	GPIO20 Pin = 20 // peripherals: PWM2 channel A, I2C0 SDA
+	GPIO21 Pin = 21 // peripherals: PWM2 channel B, I2C0 SCL
 	GPIO22 Pin = 22 // peripherals: PWM3 channel A
 	GPIO23 Pin = 23 // peripherals: PWM3 channel B
 	GPIO24 Pin = 24 // peripherals: PWM4 channel A
 	GPIO25 Pin = 25 // peripherals: PWM4 channel B
-	GPIO26 Pin = 26 // peripherals: PWM5 channel A
-	GPIO27 Pin = 27 // peripherals: PWM5 channel B
+	GPIO26 Pin = 26 // peripherals: PWM5 channel A, I2C1 SDA
+	GPIO27 Pin = 27 // peripherals: PWM5 channel B, I2C1 SCL
 	GPIO28 Pin = 28 // peripherals: PWM6 channel A
 	GPIO29 Pin = 29 // peripherals: PWM6 channel B
 )

src/machine/usb/hid/keyboard/keycode.go

@@ -209,6 +209,21 @@ const (
 	KeyF23         Keycode = 114 | 0xF000
 	KeyF24         Keycode = 115 | 0xF000
 
+	// International keys for Japanese and other language keyboards
+	KeyInternational1 Keycode = 0x87 | 0xF000 // JIS "\" and "_"
+	KeyInternational2 Keycode = 0x88 | 0xF000 // JIS Katakana/Hiragana
+	KeyInternational3 Keycode = 0x89 | 0xF000 // JIS "¥" and "|"
+	KeyInternational4 Keycode = 0x8A | 0xF000 // JIS Henkan
+	KeyInternational5 Keycode = 0x8B | 0xF000 // JIS Muhenkan
+	KeyInternational6 Keycode = 0x8C | 0xF000 // JIS Numpad ","
+
+	// Language keys for input method switching
+	KeyLanguage1 Keycode = 0x90 | 0xF000 // Hangul/English
+	KeyLanguage2 Keycode = 0x91 | 0xF000 // Hanja
+	KeyLanguage3 Keycode = 0x92 | 0xF000 // JIS Katakana
+	KeyLanguage4 Keycode = 0x93 | 0xF000 // JIS Hiragana
+	KeyLanguage5 Keycode = 0x94 | 0xF000 // JIS Zenkaku/Hankaku
+
 	KeyUpArrow    Keycode = KeyUp
 	KeyDownArrow  Keycode = KeyDown
 	KeyLeftArrow  Keycode = KeyLeft
@@ -222,6 +237,34 @@ const (
 	KeyRightShift Keycode = KeyModifierRightShift
 	KeyRightAlt   Keycode = KeyModifierRightAlt
 	KeyRightGUI   Keycode = KeyModifierRightGUI
+
+	// QMK compatibility aliases for international keys
+	KeyInt1 Keycode = KeyInternational1
+	KeyInt2 Keycode = KeyInternational2
+	KeyInt3 Keycode = KeyInternational3
+	KeyInt4 Keycode = KeyInternational4
+	KeyInt5 Keycode = KeyInternational5
+	KeyInt6 Keycode = KeyInternational6
+
+	// QMK compatibility aliases for language keys
+	KeyLng1 Keycode = KeyLanguage1
+	KeyLng2 Keycode = KeyLanguage2
+	KeyLng3 Keycode = KeyLanguage3
+	KeyLng4 Keycode = KeyLanguage4
+	KeyLng5 Keycode = KeyLanguage5
+
+	// Common keyboard layout aliases
+	KeyRo               Keycode = KeyInternational1 // Japanese "ろ"
+	KeyKatakanaHiragana Keycode = KeyInternational2 // Japanese Katakana/Hiragana
+	KeyYen              Keycode = KeyInternational3 // Japanese "¥"
+	KeyHenkan           Keycode = KeyInternational4 // Japanese Henkan
+	KeyMuhenkan         Keycode = KeyInternational5 // Japanese Muhenkan
+	KeyKpJpComma        Keycode = KeyInternational6 // Japanese Numpad ","
+	KeyHangeul          Keycode = KeyLanguage1      // Korean Hangul/English
+	KeyHanja            Keycode = KeyLanguage2      // Korean Hanja
+	KeyKatakana         Keycode = KeyLanguage3      // Japanese Katakana
+	KeyHiragana         Keycode = KeyLanguage4      // Japanese Hiragana
+	KeyZenkakuHankaku   Keycode = KeyLanguage5      // Japanese Zenkaku/Hankaku
 )
 
 // Keycodes for layout US English (0x0904)

src/runtime/gc_boehm.go

@@ -89,7 +89,7 @@ func alloc(size uintptr, layout unsafe.Pointer) unsafe.Pointer {
 	gcLock.Lock()
 	needsResumeWorld = false
 	var ptr unsafe.Pointer
-	if layout == gclayout.NoPtrs {
+	if layout == gclayout.NoPtrs.AsPtr() {
 		// This object is entirely pointer free, for example make([]int, ...).
 		// Make sure the GC knows this so it doesn't scan the object
 		// unnecessarily to improve performance.

src/runtime/slice.go

@@ -51,7 +51,7 @@ func sliceGrow(oldBuf unsafe.Pointer, oldLen, oldCap, newCap, elemSize uintptr)
 	var layout unsafe.Pointer
 	// less type info here; can only go off element size
 	if elemSize < unsafe.Sizeof(uintptr(0)) {
-		layout = gclayout.NoPtrs
+		layout = gclayout.NoPtrs.AsPtr()
 	}
 
 	buf := alloc(newCap*elemSize, layout)

src/runtime/string.go

@@ -60,7 +60,7 @@ func stringConcat(x, y _string) _string {
 		return x
 	} else {
 		length := x.length + y.length
-		buf := alloc(length, gclayout.NoPtrs)
+		buf := alloc(length, gclayout.NoPtrs.AsPtr())
 		memcpy(buf, unsafe.Pointer(x.ptr), x.length)
 		memcpy(unsafe.Add(buf, x.length), unsafe.Pointer(y.ptr), y.length)
 		return _string{ptr: (*byte)(buf), length: length}
@@ -73,7 +73,7 @@ func stringFromBytes(x struct {
 	len uintptr
 	cap uintptr
 }) _string {
-	buf := alloc(x.len, gclayout.NoPtrs)
+	buf := alloc(x.len, gclayout.NoPtrs.AsPtr())
 	memcpy(buf, unsafe.Pointer(x.ptr), x.len)
 	return _string{ptr: (*byte)(buf), length: x.len}
 }
@@ -84,7 +84,7 @@ func stringToBytes(x _string) (slice struct {
 	len uintptr
 	cap uintptr
 }) {
-	buf := alloc(x.length, gclayout.NoPtrs)
+	buf := alloc(x.length, gclayout.NoPtrs.AsPtr())
 	memcpy(buf, unsafe.Pointer(x.ptr), x.length)
 	slice.ptr = (*byte)(buf)
 	slice.len = x.length
@@ -101,7 +101,7 @@ func stringFromRunes(runeSlice []rune) (s _string) {
 	}
 
 	// Allocate memory for the string.
-	s.ptr = (*byte)(alloc(s.length, gclayout.NoPtrs))
+	s.ptr = (*byte)(alloc(s.length, gclayout.NoPtrs.AsPtr()))
 
 	// Encode runes to UTF-8 and store the resulting bytes in the string.
 	index := uintptr(0)

targets/stm32l031x6.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+  FLASH_TEXT (rx) : ORIGIN = 0x08000000, LENGTH = 32K
+  RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 8K
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/arm.ld"

targets/stm32l0x1.json

@@ -0,0 +1,18 @@
+{
+    "inherits": [
+        "cortex-m0plus"
+    ],
+    "build-tags": [
+        "stm32l031",
+        "stm32l0x1",
+        "stm32l0",
+        "stm32"
+    ],
+    "linkerscript": "targets/stm32l031x6.ld",
+    "extra-files": [
+        "src/device/stm32/stm32l0x1.s"
+    ],
+    "flash-method": "openocd",
+    "openocd-interface": "cmsis-dap",
+    "openocd-target": "stm32l0"
+}

testdata/goroutines.go

@@ -175,10 +175,13 @@ func testGoOnBuiltins() {
 
 var once sync.Once
 
+var waitChan = make(chan struct{})
+
 func testGoOnInterface(f Itf) {
 	go f.Nowait()
 	time.Sleep(time.Millisecond)
 	go f.Wait()
+	<-waitChan
 	time.Sleep(time.Millisecond * 2)
 	println("done with 'go on interface'")
 }
@@ -204,6 +207,7 @@ func (f Foo) Nowait() {
 
 func (f Foo) Wait() {
 	println("called: Foo.Wait")
+	close(waitChan)
 	time.Sleep(time.Microsecond)
 	println("  ...waited")
 }

tests/wasm/setup_test.go

@@ -36,6 +36,13 @@ func chromectx(t *testing.T) context.Context {
 	// see https://chromium.googlesource.com/chromium/src/+/main/docs/security/apparmor-userns-restrictions.md
 	opts := append(chromedp.DefaultExecAllocatorOptions[:],
 		chromedp.NoSandbox,
+		chromedp.Flag("disable-web-security", true),
+		chromedp.Flag("safebrowsing-disable-auto-update", true),
+		chromedp.IgnoreCertErrors,
+		chromedp.Flag("disable-sync", true),
+		chromedp.Flag("disable-default-apps", true),
+		chromedp.NoFirstRun,
+		chromedp.Headless,
 	)
 
 	allocCtx, cancel := chromedp.NewExecAllocator(context.Background(), opts...)