[php-src] Issue #20645: New Zend fake scope guard API proposal

Issue: https://github.com/php/php-src/issues/20645 Author: alexandre-daubois ### Description In a recent PR (#20373), we needed to use executor global fake_scope. During the review, [the following comment](https://github.com/php/php-src/pull/20373#pullrequestreview-3497642325) has been posted: > We should probably introduce some nicer api for that fake_scope as it has not been used outside > zend and reflection. It should not be directly accessed filters code IMHO but new API is more master > material... I think this makes sense. Here is how we currently use fake_scope in the code: ```c const zend_class_entry *old_scope = EG(fake_scope); EG(fake_scope) = ce; // ... EG(fake_scope) = old_scope; ``` We need to access internal Zend globals directly and the save/restore is manual and error prone. High-level wrappers exist (zend_read_property_ex, zend_update_property_ex) that already handle fake_scope internally, but they're not flexible enough for complex cases. Introducing a new API like this one would help: ```c typedef struct _zend_fake_scope_guard zend_fake_scope_guard; ZEND_API zend_fake_scope_guard *zend_fake_scope_guard_enter( const zend_class_entry *scope ); ZEND_API void zend_fake_scope_guard_exit(zend_fake_scope_guard *guard); ``` This is the kind of diff we could expect on current call sites: ```diff diff --git a/ext/reflection/php_reflection.c b/ext/reflection/php_reflection.c index d6e55c982b4..3931f648e2b 100644 --- a/ext/reflection/php_reflection.c +++ b/ext/reflection/php_reflection.c @@ -5932,11 +5932,10 @@ ZEND_METHOD(ReflectionProperty, getValue) } } - const zend_class_entry *old_scope = EG(fake_scope); - EG(fake_scope) = intern->ce; + zend_fake_scope_guard *guard = zend_fake_scope_guard_enter(intern->ce); member_p = Z_OBJ_P(object)->handlers->read_property(Z_OBJ_P(object), ref->unmangled_name, BP_VAR_R, ref->cache_slot, &rv); - EG(fake_scope) = old_scope; + zend_fake_scope_guard_exit(guard); if (member_p != &rv) { RETURN_COPY_DEREF(member_p); ``` The intent is explicit, we don't directly access executor globals and it has the same flexibility as manual save/restore. Given that we're talking about an internal Zend API, I'm not 100% sure this should follow the same process as classical RFCs and/or be announced in the internal mailing list. If yes, please let me know and I'll take care of it.