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cmd/go: add check for unknown godebug setting

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A //go:debug line mentioning an unknown or retired setting
should be diagnosed as making the program invalid. Do that.
We agreed on this in the proposal but I forgot to implement it.

Change-Id: Ie69072a1682d4eeb6866c02adbbb426f608567c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/476280
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Russ Cox 2023-03-14 14:25:56 -04:00
parent 44e51e60ac
commit 14ab998f95
21 changed files with 208 additions and 164 deletions
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38
src/internal/godebug/godebug.go
View file

@ -30,6 +30,7 @@
package godebug
import (
"internal/godebugs"
"sync"
"sync/atomic"
_ "unsafe" // go:linkname
@ -46,21 +47,38 @@ type setting struct {
value atomic.Pointer[string]
nonDefaultOnce sync.Once
nonDefault atomic.Uint64
info *godebugs.Info
}
// New returns a new Setting for the $GODEBUG setting with the given name.
//
// GODEBUGs meant for use by end users must be listed in ../godebugs/table.go,
// which is used for generating and checking various documentation.
// If the name is not listed in that table, New will succeed but calling Value
// on the returned Setting will panic.
// To disable that panic for access to an undocumented setting,
// prefix the name with a #, as in godebug.New("#gofsystrace").
// The # is a signal to New but not part of the key used in $GODEBUG.
func New(name string) *Setting {
return &Setting{name: name}
}
// Name returns the name of the setting.
func (s *Setting) Name() string {
if s.name != "" && s.name[0] == '#' {
return s.name[1:]
}
return s.name
}
// Undocumented reports whether this is an undocumented setting.
func (s *Setting) Undocumented() bool {
return s.name != "" && s.name[0] == '#'
}
// String returns a printable form for the setting: name=value.
func (s *Setting) String() string {
return s.name + "=" + s.Value()
return s.Name() + "=" + s.Value()
}
// IncNonDefault increments the non-default behavior counter
@ -69,20 +87,16 @@ func (s *Setting) String() string {
// /godebug/non-default-behavior/<name>:events.
//
// Note that Value must be called at least once before IncNonDefault.
//
// Any GODEBUG setting that can call IncNonDefault must be listed
// in three more places:
//
// - the table in ../runtime/metrics.go (search for non-default-behavior)
// - the table in ../../runtime/metrics/description.go (search for non-default-behavior; run 'go generate' afterward)
// - the table in ../../cmd/go/internal/load/godebug.go (search for defaultGodebugs)
func (s *Setting) IncNonDefault() {
s.nonDefaultOnce.Do(s.register)
s.nonDefault.Add(1)
}
func (s *Setting) register() {
registerMetric("/godebug/non-default-behavior/"+s.name+":events", s.nonDefault.Load)
if s.info == nil || s.info.Opaque {
panic("godebug: unexpected IncNonDefault of " + s.name)
}
registerMetric("/godebug/non-default-behavior/"+s.Name()+":events", s.nonDefault.Load)
}
// cache is a cache of all the GODEBUG settings,
@ -111,7 +125,10 @@ var empty string
// caching of Value's result.
func (s *Setting) Value() string {
s.once.Do(func() {
s.setting = lookup(s.name)
s.setting = lookup(s.Name())
if s.info == nil && !s.Undocumented() {
panic("godebug: Value of name not listed in godebugs.All: " + s.name)
}
})
return *s.value.Load()
}
@ -122,6 +139,7 @@ func lookup(name string) *setting {
return v.(*setting)
}
s := new(setting)
s.info = godebugs.Lookup(name)
s.value.Store(&empty)
if v, loaded := cache.LoadOrStore(name, s); loaded {
// Lost race: someone else created it. Use theirs.