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WIP: perf: copy-on-write for sentry_value_t clone #1794

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fa0e5b3
benchmark: scope & value
jpnurmi Jun 4, 2026
e7a2524
fix: clone user and fingerprint in scope_apply_to_event
jpnurmi Jun 4, 2026
6f7d4b8
ref: copy-on-write for sentry_value_t clone
jpnurmi Mar 4, 2026
201b00d
fix(value): Fix nested clone failure in thing_clone_children
jpnurmi Jun 4, 2026
409939c
fix: Handle object detach key clone failures
jpnurmi Jul 6, 2026
3e7dd7b
Update CHANGELOG.md
jpnurmi Jul 6, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@

- Native/Windows: ensure valid event IDs for fast-fail crash envelopes to fix launching of the external crash reporter for fast-fail crashes. ([#1832](https://github.com/getsentry/sentry-native/pull/1832))
- Native/Linux: resolve symbols from split-debug files on Linux. ([#1836](https://github.com/getsentry/sentry-native/pull/1836))
- Fix scope data loss from shared `sentry_value_t` containers while significantly improving scope merge performance with copy-on-write cloning. ([#1794](https://github.com/getsentry/sentry-native/pull/1794))

## 0.15.2

Expand Down
4 changes: 2 additions & 2 deletions src/sentry_scope.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,10 +414,10 @@ sentry__scope_apply_to_event(const sentry_scope_t *scope,
sentry_value_new_string(options->run->installation_id));
}
} else if (sentry_value_get_length(scope->user) > 0) {
PLACE_VALUE("user", scope->user);
PLACE_CLONED_VALUE("user", scope->user);
}
}
PLACE_VALUE("fingerprint", scope->fingerprint);
PLACE_CLONED_VALUE("fingerprint", scope->fingerprint);
PLACE_STRING("transaction", scope->transaction);
PLACE_VALUE("sdk", scope->client_sdk);

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236 changes: 206 additions & 30 deletions src/sentry_value.c
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,7 @@ typedef struct {
sentry_value_t *items;
size_t len;
size_t allocated;
long refcount;
} list_t;

typedef struct {
Expand All @@ -104,6 +105,7 @@ typedef struct {
obj_pair_t *pairs;
size_t len;
size_t allocated;
long refcount;
} obj_t;

static const char *
Expand Down Expand Up @@ -161,33 +163,148 @@ thing_get_type(const thing_t *thing)
}

static void
thing_free(thing_t *thing)
list_free(list_t *list)
{
if (sentry__atomic_fetch_and_add(&list->refcount, -1) != 1) {
return;
}
for (size_t i = 0; i < list->len; i++) {
sentry_value_decref(list->items[i]);
}
sentry_free(list->items);
sentry_free(list);
}

static void
obj_free(obj_t *obj)
{
if (sentry__atomic_fetch_and_add(&obj->refcount, -1) != 1) {
return;
}
for (size_t i = 0; i < obj->len; i++) {
sentry_free(obj->pairs[i].k);
sentry_value_decref(obj->pairs[i].v);
}
sentry_free(obj->pairs);
sentry_free(obj);
}

static bool
thing_detach(thing_t *thing)
{
switch (thing_get_type(thing)) {
case THING_TYPE_LIST: {
list_t *list = thing->payload._ptr;
for (size_t i = 0; i < list->len; i++) {
sentry_value_decref(list->items[i]);
list_t *old = thing->payload._ptr;
if (sentry__atomic_fetch(&old->refcount) <= 1) {
return true;
}
sentry_free(list->items);
sentry_free(list);
break;
list_t *new_list = SENTRY_MAKE(list_t);
if (!new_list) {
return false;
}
new_list->len = old->len;
new_list->allocated = old->len;
new_list->refcount = 1;
if (old->len) {
new_list->items = sentry_malloc(sizeof(sentry_value_t) * old->len);
if (!new_list->items) {
sentry_free(new_list);
return false;
}
memcpy(
new_list->items, old->items, sizeof(sentry_value_t) * old->len);
for (size_t i = 0; i < old->len; i++) {
sentry_value_incref(new_list->items[i]);
}
} else {
new_list->items = NULL;
}
list_free(old);
thing->payload._ptr = new_list;
return true;
}
case THING_TYPE_OBJECT: {
obj_t *obj = thing->payload._ptr;
for (size_t i = 0; i < obj->len; i++) {
sentry_free(obj->pairs[i].k);
sentry_value_decref(obj->pairs[i].v);
obj_t *old = thing->payload._ptr;
if (sentry__atomic_fetch(&old->refcount) <= 1) {
return true;
}
obj_t *new_obj = SENTRY_MAKE(obj_t);
if (!new_obj) {
return false;
}
new_obj->len = 0;
new_obj->allocated = old->len;
new_obj->refcount = 1;
if (old->len) {
new_obj->pairs = sentry_malloc(sizeof(obj_pair_t) * old->len);
if (!new_obj->pairs) {
sentry_free(new_obj);
return false;
}
for (size_t i = 0; i < old->len; i++) {
new_obj->pairs[i].k = sentry__string_clone(old->pairs[i].k);
if (!new_obj->pairs[i].k) {
obj_free(new_obj);
return false;
}
new_obj->pairs[i].v = old->pairs[i].v;
sentry_value_incref(new_obj->pairs[i].v);
new_obj->len++;
}
} else {
new_obj->pairs = NULL;
}
sentry_free(obj->pairs);
sentry_free(obj);
obj_free(old);
thing->payload._ptr = new_obj;
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return true;
}
default:
return true;
}
}

static sentry_value_t
thing_get_child(const thing_t *thing, size_t i)
{
switch (thing_get_type(thing)) {
case THING_TYPE_LIST:
return ((const list_t *)thing->payload._ptr)->items[i];
case THING_TYPE_OBJECT:
return ((const obj_t *)thing->payload._ptr)->pairs[i].v;
default:
return sentry_value_new_null();
}
}

static void
thing_set_child(thing_t *thing, size_t i, sentry_value_t value)
{
switch (thing_get_type(thing)) {
case THING_TYPE_LIST:
((list_t *)thing->payload._ptr)->items[i] = value;
break;
case THING_TYPE_OBJECT:
((obj_t *)thing->payload._ptr)->pairs[i].v = value;
break;
default:
break;
}
case THING_TYPE_STRING: {
}

static void
thing_free(thing_t *thing)
{
switch (thing_get_type(thing)) {
case THING_TYPE_LIST:
list_free(thing->payload._ptr);
break;
case THING_TYPE_OBJECT:
obj_free(thing->payload._ptr);
break;
case THING_TYPE_STRING:
sentry_free(thing->payload._ptr);
break;
}
}
sentry_free(thing);
}

Expand Down Expand Up @@ -395,6 +512,8 @@ sentry_value_new_list(void)
{
list_t *l = SENTRY_MAKE(list_t);
if (l) {
memset(l, 0, sizeof(list_t));
l->refcount = 1;
sentry_value_t rv = new_thing_value(l, THING_TYPE_LIST);
if (sentry_value_is_null(rv)) {
sentry_free(l);
Expand All @@ -410,6 +529,8 @@ sentry__value_new_list_with_size(size_t size)
{
list_t *l = SENTRY_MAKE(list_t);
if (l) {
memset(l, 0, sizeof(list_t));
l->refcount = 1;
l->allocated = size;
if (size) {
l->items = sentry_malloc(sizeof(sentry_value_t) * size);
Expand All @@ -434,6 +555,8 @@ sentry_value_new_object(void)
{
obj_t *o = SENTRY_MAKE(obj_t);
if (o) {
memset(o, 0, sizeof(obj_t));
o->refcount = 1;
sentry_value_t rv = new_thing_value(o, THING_TYPE_OBJECT);
if (sentry_value_is_null(rv)) {
sentry_free(o);
Expand All @@ -449,6 +572,8 @@ sentry__value_new_object_with_size(size_t size)
{
obj_t *o = SENTRY_MAKE(obj_t);
if (o) {
memset(o, 0, sizeof(obj_t));
o->refcount = 1;
o->allocated = size;
if (size) {
o->pairs = sentry_malloc(sizeof(obj_pair_t) * size);
Expand Down Expand Up @@ -639,7 +764,8 @@ sentry_value_set_by_key_n(
}
sentry_slice_t k_slice = { k, k_len };
thing_t *thing = value_as_unfrozen_thing(value);
if (!thing || thing_get_type(thing) != THING_TYPE_OBJECT) {
if (!thing || thing_get_type(thing) != THING_TYPE_OBJECT
|| !thing_detach(thing)) {
goto fail;
}
obj_t *o = thing->payload._ptr;
Expand Down Expand Up @@ -690,7 +816,8 @@ sentry_value_remove_by_key_n(sentry_value_t value, const char *k, size_t k_len)
}
sentry_slice_t k_slice = { k, k_len };
thing_t *thing = value_as_unfrozen_thing(value);
if (!thing || thing_get_type(thing) != THING_TYPE_OBJECT) {
if (!thing || thing_get_type(thing) != THING_TYPE_OBJECT
|| !thing_detach(thing)) {
return 1;
}
obj_t *o = thing->payload._ptr;
Expand Down Expand Up @@ -722,7 +849,8 @@ int
sentry_value_append(sentry_value_t value, sentry_value_t v)
{
thing_t *thing = value_as_unfrozen_thing(value);
if (!thing || thing_get_type(thing) != THING_TYPE_LIST) {
if (!thing || thing_get_type(thing) != THING_TYPE_LIST
|| !thing_detach(thing)) {
goto fail;
}

Expand Down Expand Up @@ -791,6 +919,42 @@ sentry__value_stringify(sentry_value_t value)
#undef STRINGIFY_NUMERIC
}

static bool
value_is_container(sentry_value_t value)
{
const thing_t *thing = value_as_thing(value);
if (!thing) {
return false;
}
int type = thing_get_type(thing);
return type == THING_TYPE_LIST || type == THING_TYPE_OBJECT;
}

static bool
thing_clone_children(thing_t *thing, size_t len)
{
bool detached = false;
for (size_t i = 0; i < len; i++) {
sentry_value_t child = thing_get_child(thing, i);
if (!value_is_container(child)) {
continue;
}
if (!detached) {
if (!thing_detach(thing)) {
return false;
}
detached = true;
}
sentry_value_t cloned = sentry__value_clone(child);
if (sentry_value_is_null(cloned)) {
return false;
}
sentry_value_decref(child);
thing_set_child(thing, i, cloned);
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}
return true;
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}

sentry_value_t
sentry__value_clone(sentry_value_t value)
{
Expand All @@ -800,20 +964,30 @@ sentry__value_clone(sentry_value_t value)
}
switch (thing_get_type(thing)) {
case THING_TYPE_LIST: {
const list_t *list = thing->payload._ptr;
sentry_value_t rv = sentry__value_new_list_with_size(list->len);
for (size_t i = 0; i < list->len; i++) {
sentry_value_incref(list->items[i]);
sentry_value_append(rv, list->items[i]);
list_t *list = thing->payload._ptr;
sentry__atomic_fetch_and_add(&list->refcount, 1);
sentry_value_t rv = new_thing_value(list, THING_TYPE_LIST);
if (sentry_value_is_null(rv)) {
list_free(list);
return rv;
}
if (!thing_clone_children(value_as_thing(rv), list->len)) {
sentry_value_decref(rv);
return sentry_value_new_null();
}
return rv;
}
case THING_TYPE_OBJECT: {
const obj_t *obj = thing->payload._ptr;
sentry_value_t rv = sentry__value_new_object_with_size(obj->len);
for (size_t i = 0; i < obj->len; i++) {
sentry_value_incref(obj->pairs[i].v);
sentry_value_set_by_key(rv, obj->pairs[i].k, obj->pairs[i].v);
obj_t *obj = thing->payload._ptr;
sentry__atomic_fetch_and_add(&obj->refcount, 1);
sentry_value_t rv = new_thing_value(obj, THING_TYPE_OBJECT);
if (sentry_value_is_null(rv)) {
obj_free(obj);
return rv;
}
if (!thing_clone_children(value_as_thing(rv), obj->len)) {
sentry_value_decref(rv);
return sentry_value_new_null();
}
return rv;
}
Expand All @@ -832,7 +1006,8 @@ int
sentry_value_set_by_index(sentry_value_t value, size_t index, sentry_value_t v)
{
thing_t *thing = value_as_unfrozen_thing(value);
if (!thing || thing_get_type(thing) != THING_TYPE_LIST) {
if (!thing || thing_get_type(thing) != THING_TYPE_LIST
|| !thing_detach(thing)) {
goto fail;
}

Expand Down Expand Up @@ -862,7 +1037,8 @@ int
sentry_value_remove_by_index(sentry_value_t value, size_t index)
{
thing_t *thing = value_as_unfrozen_thing(value);
if (!thing || thing_get_type(thing) != THING_TYPE_LIST) {
if (!thing || thing_get_type(thing) != THING_TYPE_LIST
|| !thing_detach(thing)) {
return 1;
}

Expand Down
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