runtime: handle GODEBUG on wasip2 (#5312)

* runtime: handle GODEBUG on wasip2
* Support env on more platforms to get GODEBUG working

GNUmakefile

@@ -488,7 +488,7 @@ TEST_PACKAGES_HOST := $(TEST_PACKAGES_FAST) $(TEST_PACKAGES_WINDOWS)
 TEST_IOFS := false
 endif
 
-TEST_SKIP_FLAG := -skip='TestExtraMethods|TestParseAndBytesRoundTrip/P256/Generic|TestParseQueryLimits|TestParseStrictIpv6|TestAsValidation'
+TEST_SKIP_FLAG := -skip='TestExtraMethods|TestParseAndBytesRoundTrip/P256/Generic|TestAsValidation'
 TEST_ADDITIONAL_FLAGS ?=
 
 # Test known-working standard library packages.

src/runtime/env.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin || windows || wasip1
+//go:build (linux || darwin || windows || wasip1) && !wasip2 && !baremetal && !wasm_unknown
 
 package runtime
 

src/runtime/env_nonhosted.go

@@ -0,0 +1,43 @@
+//go:build baremetal || js || wasm_unknown
+
+package runtime
+
+//go:linkname syscallSetenv syscall.runtimeSetenv
+func syscallSetenv(key, value string) {
+	entry := key + "=" + value
+	for i, e := range env {
+		if envKey(e) == key {
+			env[i] = entry
+			if key == "GODEBUG" && godebugUpdate != nil {
+				godebugUpdate(key, value)
+			}
+			return
+		}
+	}
+	env = append(env, entry)
+	if key == "GODEBUG" && godebugUpdate != nil {
+		godebugUpdate(key, value)
+	}
+}
+
+//go:linkname syscallUnsetenv syscall.runtimeUnsetenv
+func syscallUnsetenv(key string) {
+	for i, e := range env {
+		if envKey(e) == key {
+			env = append(env[:i], env[i+1:]...)
+			if key == "GODEBUG" && godebugUpdate != nil {
+				godebugUpdate(key, "")
+			}
+			return
+		}
+	}
+}
+
+func envKey(entry string) string {
+	for i := 0; i < len(entry); i++ {
+		if entry[i] == '=' {
+			return entry[:i]
+		}
+	}
+	return entry
+}

src/runtime/env_wasip2.go

@@ -0,0 +1,21 @@
+//go:build wasip2
+
+package runtime
+
+// Notify the runtime when environment variables change.
+// On wasip2, the environment is managed in Go (no C setenv), but
+// internal/godebug still needs to be notified of GODEBUG changes.
+
+//go:linkname syscallSetenv syscall.runtimeSetenv
+func syscallSetenv(key, value string) {
+	if key == "GODEBUG" && godebugUpdate != nil {
+		godebugUpdate(key, value)
+	}
+}
+
+//go:linkname syscallUnsetenv syscall.runtimeUnsetenv
+func syscallUnsetenv(key string) {
+	if key == "GODEBUG" && godebugUpdate != nil {
+		godebugUpdate(key, "")
+	}
+}

src/syscall/env_nonhosted.go

@@ -28,18 +28,38 @@ func Getenv(key string) (value string, found bool) {
 }
 
 func Setenv(key, val string) (err error) {
-	// stub for now
-	return ENOSYS
+	if len(key) == 0 {
+		return EINVAL
+	}
+	for i := 0; i < len(key); i++ {
+		if key[i] == '=' || key[i] == 0 {
+			return EINVAL
+		}
+	}
+	for i := 0; i < len(val); i++ {
+		if val[i] == 0 {
+			return EINVAL
+		}
+	}
+	runtimeSetenv(key, val)
+	return nil
 }
 
 func Unsetenv(key string) (err error) {
-	// stub for now
-	return ENOSYS
+	runtimeUnsetenv(key)
+	return nil
 }
 
 func Clearenv() (err error) {
-	// stub for now
-	return ENOSYS
+	for _, s := range Environ() {
+		for j := 0; j < len(s); j++ {
+			if s[j] == '=' {
+				Unsetenv(s[:j])
+				break
+			}
+		}
+	}
+	return nil
 }
 
 func runtime_envs() []string

src/syscall/env_wasip2.go

@@ -43,11 +43,13 @@ func Setenv(key, val string) (err error) {
 		}
 	}
 	libc_envs[key] = val
+	runtimeSetenv(key, val)
 	return nil
 }
 
 func Unsetenv(key string) (err error) {
 	delete(libc_envs, key)
+	runtimeUnsetenv(key)
 	return nil
 }
 

src/syscall/syscall_nonhosted.go

@@ -176,3 +176,7 @@ type RawSockaddrInet4 struct {
 type RawSockaddrInet6 struct {
 	// stub
 }
+
+// These two functions are provided by the runtime.
+func runtimeSetenv(key, value string)
+func runtimeUnsetenv(key string)