os, syscall: add Unsetenv
Also address a TODO, making Clearenv pass through to cgo.
Based largely on Minux's earlier https://golang.org/cl/82040044
Fixes #6423
LGTM=iant, alex.brainman, r, rsc
R=rsc, iant, r, alex.brainman
CC=golang-codereviews
https://golang.org/cl/148370043
diff --git a/src/os/env.go b/src/os/env.go
index db7fc72..d0494a4 100644
--- a/src/os/env.go
+++ b/src/os/env.go
@@ -91,6 +91,11 @@
return nil
}
+// Unsetenv unsets a single environment variable.
+func Unsetenv(key string) error {
+ return syscall.Unsetenv(key)
+}
+
// Clearenv deletes all environment variables.
func Clearenv() {
syscall.Clearenv()
diff --git a/src/os/env_test.go b/src/os/env_test.go
index 991fa4d..e618067 100644
--- a/src/os/env_test.go
+++ b/src/os/env_test.go
@@ -7,6 +7,7 @@
import (
. "os"
"reflect"
+ "strings"
"testing"
)
@@ -68,3 +69,28 @@
}
}
}
+
+func TestUnsetenv(t *testing.T) {
+ const testKey = "GO_TEST_UNSETENV"
+ set := func() bool {
+ prefix := testKey + "="
+ for _, key := range Environ() {
+ if strings.HasPrefix(key, prefix) {
+ return true
+ }
+ }
+ return false
+ }
+ if err := Setenv(testKey, "1"); err != nil {
+ t.Fatalf("Setenv: %v", err)
+ }
+ if !set() {
+ t.Error("Setenv didn't set TestUnsetenv")
+ }
+ if err := Unsetenv(testKey); err != nil {
+ t.Fatalf("Unsetenv: %v", err)
+ }
+ if set() {
+ t.Fatal("Unsetenv didn't clear TestUnsetenv")
+ }
+}
diff --git a/src/runtime/cgo/gcc_setenv.c b/src/runtime/cgo/gcc_setenv.c
index 8b128b9..af0fc5d 100644
--- a/src/runtime/cgo/gcc_setenv.c
+++ b/src/runtime/cgo/gcc_setenv.c
@@ -14,3 +14,10 @@
{
setenv(arg[0], arg[1], 1);
}
+
+/* Stub for calling unsetenv */
+void
+x_cgo_unsetenv(char *arg)
+{
+ unsetenv(arg);
+}
diff --git a/src/runtime/cgo/setenv.c b/src/runtime/cgo/setenv.c
index ee52990..76d88cb 100644
--- a/src/runtime/cgo/setenv.c
+++ b/src/runtime/cgo/setenv.c
@@ -5,6 +5,9 @@
// +build darwin dragonfly freebsd linux netbsd openbsd
#pragma cgo_import_static x_cgo_setenv
+#pragma cgo_import_static x_cgo_unsetenv
void x_cgo_setenv(char**);
void (*runtime·_cgo_setenv)(char**) = x_cgo_setenv;
+void x_cgo_unsetenv(char**);
+void (*runtime·_cgo_unsetenv)(char**) = x_cgo_unsetenv;
diff --git a/src/runtime/env_posix.go b/src/runtime/env_posix.go
index 6c04f6c..dd57872 100644
--- a/src/runtime/env_posix.go
+++ b/src/runtime/env_posix.go
@@ -32,7 +32,8 @@
return ""
}
-var _cgo_setenv uintptr // pointer to C function
+var _cgo_setenv uintptr // pointer to C function
+var _cgo_unsetenv uintptr // pointer to C function
// Update the C environment if cgo is loaded.
// Called from syscall.Setenv.
@@ -44,6 +45,16 @@
asmcgocall(unsafe.Pointer(_cgo_setenv), unsafe.Pointer(&arg))
}
+// Update the C environment if cgo is loaded.
+// Called from syscall.unsetenv.
+func syscall_unsetenv_c(k string) {
+ if _cgo_unsetenv == 0 {
+ return
+ }
+ arg := [1]unsafe.Pointer{cstring(k)}
+ asmcgocall(unsafe.Pointer(_cgo_unsetenv), unsafe.Pointer(&arg))
+}
+
func cstring(s string) unsafe.Pointer {
p := make([]byte, len(s)+1)
sp := (*_string)(unsafe.Pointer(&s))
diff --git a/src/runtime/thunk.s b/src/runtime/thunk.s
index d6a2d39..0a0f147 100644
--- a/src/runtime/thunk.s
+++ b/src/runtime/thunk.s
@@ -110,6 +110,9 @@
TEXT syscall·setenv_c(SB), NOSPLIT, $0-0
JMP runtime·syscall_setenv_c(SB)
+TEXT syscall·unsetenv_c(SB), NOSPLIT, $0-0
+ JMP runtime·syscall_unsetenv_c(SB)
+
TEXT reflect·makemap(SB),NOSPLIT,$0-0
JMP runtime·reflect_makemap(SB)
diff --git a/src/syscall/env_plan9.go b/src/syscall/env_plan9.go
index 9587ab5..3044b41 100644
--- a/src/syscall/env_plan9.go
+++ b/src/syscall/env_plan9.go
@@ -12,16 +12,22 @@
)
var (
- // envOnce guards copyenv, which populates env.
+ // envOnce guards copyenv, which populates env, envi and envs.
envOnce sync.Once
- // envLock guards env and envs.
+ // envLock guards env, envi and envs.
envLock sync.RWMutex
// env maps from an environment variable to its value.
+ // TODO: remove this? golang.org/issue/8849
env = make(map[string]string)
+ // envi maps from an environment variable to its index in envs.
+ // TODO: remove this? golang.org/issue/8849
+ envi = make(map[string]int)
+
// envs contains elements of env in the form "key=value".
+ // empty strings mean deleted.
envs []string
errZeroLengthKey = errors.New("zero length key")
@@ -83,6 +89,7 @@
}
env[key] = v
envs[i] = key + "=" + v
+ envi[key] = i
i++
}
}
@@ -129,14 +136,39 @@
defer envLock.Unlock()
env = make(map[string]string)
+ envi = make(map[string]int)
envs = []string{}
RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
}
+func Unsetenv(key string) error {
+ if len(key) == 0 {
+ return errZeroLengthKey
+ }
+
+ envLock.Lock()
+ defer envLock.Unlock()
+
+ Remove("/env/" + key)
+
+ if i, ok := envi[key]; ok {
+ delete(env, key)
+ delete(envi, key)
+ envs[i] = ""
+ }
+ return nil
+}
+
func Environ() []string {
envLock.RLock()
defer envLock.RUnlock()
envOnce.Do(copyenv)
- return append([]string(nil), envs...)
+ ret := make([]string, 0, len(envs))
+ for _, pair := range envs {
+ if pair != "" {
+ ret = append(ret, pair)
+ }
+ }
+ return ret
}
diff --git a/src/syscall/env_unix.go b/src/syscall/env_unix.go
index 01ac38a..b5ded9c 100644
--- a/src/syscall/env_unix.go
+++ b/src/syscall/env_unix.go
@@ -20,16 +20,18 @@
// env maps from an environment variable to its first occurrence in envs.
env map[string]int
- // envs is provided by the runtime. elements are expected to be
- // of the form "key=value".
+ // envs is provided by the runtime. elements are expected to
+ // be of the form "key=value". An empty string means deleted
+ // (or a duplicate to be ignored).
envs []string = runtime_envs()
)
func runtime_envs() []string // in package runtime
-// setenv_c is provided by the runtime, but is a no-op if cgo isn't
-// loaded.
+// setenv_c and unsetenv_c are provided by the runtime but are no-ops
+// if cgo isn't loaded.
func setenv_c(k, v string)
+func unsetenv_c(k string)
func copyenv() {
env = make(map[string]int)
@@ -38,7 +40,13 @@
if s[j] == '=' {
key := s[:j]
if _, ok := env[key]; !ok {
- env[key] = i
+ env[key] = i // first mention of key
+ } else {
+ // Clear duplicate keys. This permits Unsetenv to
+ // safely delete only the first item without
+ // worrying about unshadowing a later one,
+ // which might be a security problem.
+ envs[i] = ""
}
break
}
@@ -46,6 +54,20 @@
}
}
+func Unsetenv(key string) error {
+ envOnce.Do(copyenv)
+
+ envLock.Lock()
+ defer envLock.Unlock()
+
+ if i, ok := env[key]; ok {
+ envs[i] = ""
+ delete(env, key)
+ }
+ unsetenv_c(key)
+ return nil
+}
+
func Getenv(key string) (value string, found bool) {
envOnce.Do(copyenv)
if len(key) == 0 {
@@ -106,16 +128,22 @@
envLock.Lock()
defer envLock.Unlock()
+ for k := range env {
+ unsetenv_c(k)
+ }
env = make(map[string]int)
envs = []string{}
- // TODO(bradfitz): pass through to C
}
func Environ() []string {
envOnce.Do(copyenv)
envLock.RLock()
defer envLock.RUnlock()
- a := make([]string, len(envs))
- copy(a, envs)
+ a := make([]string, 0, len(envs))
+ for _, env := range envs {
+ if env != "" {
+ a = append(a, env)
+ }
+ }
return a
}
diff --git a/src/syscall/env_windows.go b/src/syscall/env_windows.go
index 420b387..bc21690 100644
--- a/src/syscall/env_windows.go
+++ b/src/syscall/env_windows.go
@@ -47,6 +47,14 @@
return nil
}
+func Unsetenv(key string) error {
+ keyp, err := UTF16PtrFromString(key)
+ if err != nil {
+ return err
+ }
+ return SetEnvironmentVariable(keyp, nil)
+}
+
func Clearenv() {
for _, s := range Environ() {
// Environment variables can begin with =
