windows: add support for syscall.runtimeSetenv

I missed this in #3391 (because
I didn't test on Windows, my fault).

Author: aykevl

src/runtime/env_unix.go renamed to src/runtime/env.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin
+//go:build linux || darwin || windows
 
 package runtime
 
@@ -9,8 +9,7 @@ package runtime
 func syscallSetenv(key, value string) {
 	keydata := cstring(key)
 	valdata := cstring(value)
-	// ignore any errors
-	libc_setenv(&keydata[0], &valdata[0], 1)
+	setenv(&keydata[0], &valdata[0])
 	if key == "GODEBUG" && godebugUpdate != nil {
 		// Starting with Go 1.20, we need to call a callback (set by
 		// internal/godebug) to notify the GODEBUG environment variable has
@@ -25,8 +24,7 @@ func syscallSetenv(key, value string) {
 //go:linkname syscallUnsetenv syscall.runtimeUnsetenv
 func syscallUnsetenv(key string) {
 	keydata := cstring(key)
-	// ignore any errors
-	libc_unsetenv(&keydata[0])
+	unsetenv(&keydata[0])
 }
 
 // Compatibility with Go 1.19 and below.
@@ -51,13 +49,3 @@ func cstring(s string) []byte {
 	// final byte should be zero from the initial allocation
 	return data
 }
-
-// int setenv(const char *name, const char *val, int replace);
-//
-//export setenv
-func libc_setenv(name *byte, val *byte, replace int32) int32
-
-// int unsetenv(const char *name);
-//
-//export unsetenv
-func libc_unsetenv(name *byte) int32

src/runtime/os_windows.go

@@ -7,6 +7,16 @@ const GOOS = "windows"
 //export GetModuleHandleExA
 func _GetModuleHandleExA(dwFlags uint32, lpModuleName unsafe.Pointer, phModule **exeHeader) bool
 
+// Set environment variable in Windows:
+//
+//	BOOL SetEnvironmentVariableA(
+//	    [in]           LPCSTR lpName,
+//	    [in, optional] LPCSTR lpValue
+//	);
+//
+//export SetEnvironmentVariableA
+func _SetEnvironmentVariableA(key, val *byte) bool
+
 // MS-DOS stub with PE header offset:
 // https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#ms-dos-stub-image-only
 type exeHeader struct {
@@ -113,3 +123,13 @@ func syscall_Getpagesize() int {
 	_GetSystemInfo(unsafe.Pointer(&info))
 	return int(info.dwpagesize)
 }
+
+func setenv(key, val *byte) {
+	// ignore any errors
+	_SetEnvironmentVariableA(key, val)
+}
+
+func unsetenv(key *byte) {
+	// ignore any errors
+	_SetEnvironmentVariableA(key, nil)
+}

src/runtime/runtime_unix.go

@@ -150,6 +150,26 @@ func syscall_runtime_envs() []string {
 	return envs
 }
 
+// int setenv(const char *name, const char *val, int replace);
+//
+//export setenv
+func libc_setenv(name *byte, val *byte, replace int32) int32
+
+// int unsetenv(const char *name);
+//
+//export unsetenv
+func libc_unsetenv(name *byte) int32
+
+func setenv(key, val *byte) {
+	// ignore any errors
+	libc_setenv(key, val, 1)
+}
+
+func unsetenv(key *byte) {
+	// ignore any errors
+	libc_unsetenv(key)
+}
+
 func putchar(c byte) {
 	buf := [1]byte{c}
 	libc_write(1, unsafe.Pointer(&buf[0]), 1)