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Bug 1570575 - Some libpref tidy-ups. r=KrisWright
This commit: - improves the wording of some comments; - renames `UpdatePolicy` as `MirrorKind`, to reflect the new terminology we are starting to use; - does a couple of other minor clean-ups. Differential Revision: https://phabricator.services.mozilla.com/D40161 --HG-- extra : moz-landing-system : lando
This commit is contained in:
Nicholas Nethercote
parent
905c456380
commit
605fd328b4
@ -1201,8 +1201,8 @@ using PrefsHashTable = HashSet<UniquePtr<Pref>, PrefHasher>;
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static PrefsHashTable* gHashTable;
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#ifdef DEBUG
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// This defines the datatype used to store our `Once` StaticPrefs checker.
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// We can't use HashMap for now due to alignment restrictions when dealing with
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// This defines the type used to store our `once` mirrors checker. We can't use
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// HashMap for now due to alignment restrictions when dealing with
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// std::function<void()> (see bug 1557617).
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typedef std::function<void()> AntiFootgunCallback;
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struct CompareStr {
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@ -1707,9 +1707,9 @@ static void NotifyCallbacks(const char* aPrefName, const PrefWrapper* aPref) {
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if (XRE_IsParentProcess() &&
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!StaticPrefs::preferences_force_disable_check_once_policy() &&
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(StaticPrefs::preferences_check_once_policy() || xpc::IsInAutomation())) {
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// Check that we aren't modifying a `Once` pref using that prefName.
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// We have about 100 `Once` StaticPrefs defined. std::map performs a search
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// in O(log n), so this is fast enough for our case.
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// Check that we aren't modifying a `once`-mirrored pref using that pref
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// name. We have about 100 `once`-mirrored prefs. std::map performs a
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// search in O(log n), so this is fast enough.
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MOZ_ASSERT(gOnceStaticPrefsAntiFootgun);
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auto search = gOnceStaticPrefsAntiFootgun->find(aPrefName);
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if (search != gOnceStaticPrefsAntiFootgun->end()) {
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@ -3724,8 +3724,8 @@ FileDescriptor Preferences::EnsureSnapshot(size_t* aSize) {
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iter.get()->AddToMap(builder);
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}
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// Store the current value of Once StaticPrefs. Following this those
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// StaticPrefs will become immutable.
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// Store the current value of `once`-mirrored prefs. After this point they
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// will be immutable.
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StaticPrefs::RegisterOncePrefs(builder);
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gSharedMap = new SharedPrefMap(std::move(builder));
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@ -5371,34 +5371,24 @@ static void InitPref(const char* aName, float aDefaultValue) {
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}
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template <typename T>
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static void InitVarCachePref(StaticPrefs::UpdatePolicy aPolicy,
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static void InitMirroredPref(StaticPrefs::MirrorKind aPolicy,
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const nsACString& aName, T* aCache,
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StripAtomic<T> aDefaultValue, bool aIsStartup,
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bool aIsParent) {
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// aIsStartup will be true when we first initialize the StaticPrefs and false
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// when we want to reset the Preferences/StaticPrefs to their default value.
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// InitVarCachePref is called under the following scenarios:
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// aIsParent | aIsStartup | Action
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// true | true | Set underlying preference and StaticPrefs to
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// | | their default value, set callback for Live pref.
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// true | false | reset underlying preference and StaticPref to
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// | | default value.
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// false | true | set callback for Live pref.
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// false | false | none.
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//
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// We only set *aCache if the policy is Live as:
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// 1- On startup, `Once` prefs will be initialized lazily in InitOncePrefs(),
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// 2- After that, `Once` prefs are immutable.
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// In the parent process, set/reset the pref value and the `always` mirror (if
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// there is one) to the default value.
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// - `once` mirrors will be initialized lazily in InitOncePrefs().
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// - In child processes, the parent sends the correct initial values via
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// shared memory, so we do not re-initialize them here.
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if (aIsParent) {
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InitPref(PromiseFlatCString(aName).get(), aDefaultValue);
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if (MOZ_LIKELY(aPolicy == StaticPrefs::UpdatePolicy::Live)) {
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if (MOZ_LIKELY(aPolicy == StaticPrefs::MirrorKind::Always)) {
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*aCache = aDefaultValue;
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}
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}
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if (MOZ_LIKELY(aPolicy == StaticPrefs::UpdatePolicy::Live) &&
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// At startup, setup the callback for the `always` mirror (if there is one).
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if (MOZ_LIKELY(aPolicy == StaticPrefs::MirrorKind::Always) &&
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MOZ_LIKELY(aIsStartup)) {
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AddVarCacheNoAssignment(aCache, aName, aDefaultValue);
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}
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@ -5411,7 +5401,8 @@ namespace StaticPrefs {
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void MaybeInitOncePrefs() {
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if (MOZ_LIKELY(sOncePrefRead)) {
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// `Once` StaticPrefs have already been initialized to their default value.
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// `once`-mirrored prefs have already been initialized to their default
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// value.
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return;
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}
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StaticMutexAutoLock lock(sOncePrefMutex);
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@ -5429,14 +5420,14 @@ void MaybeInitOncePrefs() {
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// For a pref like this:
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//
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate a variable definition like this:
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//
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// int32_t sVarCache_my_pref(99);
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//
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#define PREF(name, cpp_type, value)
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#define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, default_value) \
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#define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, default_value) \
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cpp_type sVarCache_##full_id(default_value);
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#include "mozilla/StaticPrefListAll.h"
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#undef PREF
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@ -5450,19 +5441,19 @@ static void InitAll(bool aIsStartup) {
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// For prefs like these:
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//
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// PREF("foo.bar.baz", bool, true)
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate registration calls like this:
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//
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// if (isParent) {
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// InitPref_bool("foo.bar.baz", true);
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// }
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// InitVarCachePref(UpdatePolicy::Live, "my.pref", &sVarCache_my_pref,
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// 99, aIsStartup, isParent);
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// InitMirroredPref($MIRROR, "my.pref", &sVarCache_my_pref, 99, aIsStartup,
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// isParent);
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//
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// The InitPref_*() functions have a type suffix to avoid ambiguity between
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// prefs having int32_t and float default values. That suffix is not needed
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// for the InitVarCachePref() functions because they take a pointer parameter,
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// for the InitMirroredPref() functions because they take a pointer parameter,
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// which prevents automatic int-to-float coercion.
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//
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// In content processes, we rely on the parent to send us the correct initial
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@ -5471,8 +5462,8 @@ static void InitAll(bool aIsStartup) {
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if (isParent) { \
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InitPref_##cpp_type(name, value); \
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}
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#define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, value) \
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InitVarCachePref(UpdatePolicy::policy, NS_LITERAL_CSTRING(name), \
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#define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, value) \
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InitMirroredPref(MirrorKind::mirror, NS_LITERAL_CSTRING(name), \
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&sVarCache_##full_id, value, aIsStartup, isParent);
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#include "mozilla/StaticPrefListAll.h"
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#undef PREF
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@ -5482,26 +5473,27 @@ static void InitAll(bool aIsStartup) {
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static void InitOncePrefs() {
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// For a pref like this:
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//
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate an initialization (in a non-DEBUG build) like this:
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// we generate a non-DEBUG initialization like this:
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//
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// if (UpdatePolicy::$POLICY == UpdatePolicy::Once) {
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// if (MirrorKind::$MIRROR == MirrorKind::Once) {
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// sVarCache_my_pref = Internals::GetPref("my.pref", 99);
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// }
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//
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// This is done to get the potentially updated Preference value as we didn't
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// register a callback method for the `Once` policy.
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// This is done in case the pref value was updated when reading pref data
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// files. It's necessary because we don't have callbacks registered for
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// `once`-mirrored prefs.
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//
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// On debug build, we also install a mechanism that allows to check if the
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// original Preference is being modified once `Once` StaticPrefs have been
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// initialized as this would indicate a likely misuse of `Once` StaticPrefs
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// and that maybe instead they should have been made `Live`.
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// In debug builds, we also install a mechanism that can check if the
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// preference value is modified after `once`-mirrored prefs are initialized.
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// In tests this would indicate a likely misuse of a `once`-mirrored pref and
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// suggest that it should instead be `always`-mirrored.
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//
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#define PREF(name, cpp_type, value)
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#ifdef DEBUG
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# define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, value) \
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if (UpdatePolicy::policy == UpdatePolicy::Once) { \
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# define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, value) \
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if (MirrorKind::mirror == MirrorKind::Once) { \
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MOZ_ASSERT(gOnceStaticPrefsAntiFootgun); \
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sVarCache_##full_id = \
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Internals::GetPref(name, StripAtomic<cpp_type>(value)); \
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@ -5521,8 +5513,8 @@ static void InitOncePrefs() {
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std::move(checkPref))); \
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}
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#else
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# define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, value) \
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if (UpdatePolicy::policy == UpdatePolicy::Once) { \
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# define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, value) \
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if (MirrorKind::mirror == MirrorKind::Once) { \
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sVarCache_##full_id = \
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Internals::GetPref(name, StripAtomic<cpp_type>(value)); \
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}
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@ -5596,24 +5588,25 @@ static void RegisterOncePrefs(SharedPrefMapBuilder& aBuilder) {
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// For a pref like this:
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//
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate a save call like this:
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//
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// if (UpdatePolicy::$POLICY == UpdatePolicy::Once) {
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// if (MirrorKind::$MIRROR == MirrorKind::Once) {
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// SaveOncePrefToSharedMap(aBuilder, ONCE_PREF_NAME(my.pref),
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// sVarCache_my_pref);
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// }
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//
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// `Once` StaticPrefs values will be stored in a hidden and locked preferences
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// in the global SharedPreferenceMap. In order for those preferences to be
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// hidden and not appear in about:config nor ever be stored to disk, we add
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// the "$$$" prefix and suffix to the preference name and set the IsVisible
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// flag to false.
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// This saves the `once`-mirrored value as it was at parent startup. It is
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// stored in a special (hidden and locked) entry in the global
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// SharedPreferenceMap. In order for the entry to be hidden and not appear in
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// about:config nor ever be stored to disk, we set its IsSkippedByIteration
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// flag to true. We also distinguish it by adding a "$$$" prefix and suffix
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// to the preference name.
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//
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#define PREF(name, cpp_type, value)
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#define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, value) \
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if (UpdatePolicy::policy == UpdatePolicy::Once) { \
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#define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, value) \
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if (MirrorKind::mirror == MirrorKind::Once) { \
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SaveOncePrefToSharedMap(aBuilder, ONCE_PREF_NAME(name), \
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StripAtomic<cpp_type>(sVarCache_##full_id)); \
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}
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@ -5629,43 +5622,37 @@ static void InitStaticPrefsFromShared() {
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// For a prefs like this:
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//
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate an initialization like this:
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//
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// {
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// int32_t val;
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// nsresult rv;
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// if (UpdatePolicy::$POLICY == UpdatePolicy::Once) {
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// rv = Internals::GetSharedPrefValue(
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// "$$$my.pref$$$", &val);
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// } else if (UpdatePolicy::Once == UpdatePolicy::Live) {
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// rv = Internals::GetSharedPrefValue("my.pref", &val);
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// }
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// nsresult rv = (MirrorKind::$MIRROR == MirrorKind::Once)
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// ? Internals::GetSharedPrefValue("$$$my.pref$$$", &val)
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// : Internals::GetSharedPrefValue("my.pref", &val);
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// MOZ_DIAGNOSTIC_ALWAYS_TRUE(NS_SUCCEEDED(rv));
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// sVarCache_my_pref = val;
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// }
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//
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#define PREF(name, cpp_type, value)
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#define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, value) \
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{ \
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StripAtomic<cpp_type> val; \
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nsresult rv; \
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if (UpdatePolicy::policy == UpdatePolicy::Once) { \
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rv = Internals::GetSharedPrefValue(ONCE_PREF_NAME(name), &val); \
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} else { \
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rv = Internals::GetSharedPrefValue(name, &val); \
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} \
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MOZ_DIAGNOSTIC_ALWAYS_TRUE(NS_SUCCEEDED(rv)); \
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StaticPrefs::sVarCache_##full_id = val; \
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#define VARCACHE_PREF(mirror, name, base_id, full_id, cpp_type, value) \
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{ \
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StripAtomic<cpp_type> val; \
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nsresult rv = \
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(MirrorKind::mirror == MirrorKind::Once) \
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? Internals::GetSharedPrefValue(ONCE_PREF_NAME(name), &val) \
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: Internals::GetSharedPrefValue(name, &val); \
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MOZ_DIAGNOSTIC_ALWAYS_TRUE(NS_SUCCEEDED(rv)); \
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StaticPrefs::sVarCache_##full_id = val; \
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}
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#include "mozilla/StaticPrefListAll.h"
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#undef PREF
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#undef VARCACHE_PREF
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// `Once` StaticPrefs have been set to their value in the step above and
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// outside the parent process they are immutable. So we set sOncePrefRead
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// so that we can directly skip any lazy initializations.
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// `once`-mirrored prefs have been set to their value in the step above and
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// outside the parent process they are immutable. We set sOncePrefRead so
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// that we can directly skip any lazy initializations.
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sOncePrefRead = true;
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}
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@ -64,10 +64,17 @@ struct IsAtomic<std::atomic<T>> : TrueType {};
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namespace StaticPrefs {
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// Undo X11/X.h's definition of `Always` so we can use it in `MirrorKind`.
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#undef Always
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// Enums for the update policy.
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enum class UpdatePolicy {
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Once, // Evaluate the preference once, unchanged during the session.
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Live // Evaluate the preference and set callback so it stays current/live.
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enum class MirrorKind {
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// Mirror the pref value once, at startup.
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Once,
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// Mirror the pref vale always, with live updating. This would be `Always`,
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// but /usr/include/X11/X.h defines a macro with that name.
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Always
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};
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void MaybeInitOncePrefs();
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@ -16,14 +16,14 @@ namespace StaticPrefs {
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// For a VarCache pref like this:
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//
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// VARCACHE_PREF($POLICY, "my.pref", my_pref, my_pref, int32_t, 99)
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// VARCACHE_PREF($MIRROR, "my.pref", my_pref, my_pref, int32_t, 99)
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//
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// we generate an extern variable declaration and three getter
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// declarations/definitions.
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//
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// extern int32_t sVarCache_my_pref;
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// inline int32_t my_pref() {
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// if (UpdatePolicy::$POLICY != UpdatePolicy::Once) {
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// if (MirrorKind::$MIRROR != MirrorKind::Once) {
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// return sVarCache_my_pref;
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// }
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// MaybeInitOncePrefs();
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@ -39,7 +39,7 @@ namespace StaticPrefs {
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#define VARCACHE_PREF(policy, name, base_id, full_id, cpp_type, default_value) \
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extern cpp_type sVarCache_##full_id; \
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inline StripAtomic<cpp_type> full_id() { \
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if (UpdatePolicy::policy != UpdatePolicy::Once) { \
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if (MirrorKind::policy != MirrorKind::Once) { \
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MOZ_DIAGNOSTIC_ASSERT( \
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IsAtomic<cpp_type>::value || NS_IsMainThread(), \
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"Non-atomic static pref '" name \
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@ -65,7 +65,7 @@ VARCACHE_PREF(
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'always': '''\
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VARCACHE_PREF(
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Live,
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Always,
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"{name}",
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{base_id},
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{full_id},
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@ -100,7 +100,7 @@ VARCACHE_PREF(
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)
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VARCACHE_PREF(
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Live,
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Always,
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"my.uint",
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my_uint,
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my_uint,
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@ -120,7 +120,7 @@ PREF("my.string", String, "foo\\"bar")
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PREF("my.string2", String, "foobar")
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VARCACHE_PREF(
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Live,
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Always,
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"my.atomic.bool",
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my_atomic_bool,
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my_atomic_bool,
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@ -128,7 +128,7 @@ VARCACHE_PREF(
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)
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VARCACHE_PREF(
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Live,
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Always,
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"my.atomic.int",
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my_atomic_int,
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my_atomic_int_DoNotUseDirectly,
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