[php-src] Issue #24211: Potential SIGN_EXTENSION in SplFixedArray::__serialize()

Issue: https://github.com/php/php-src/issues/24211 Author: Ti-Mis ### Description Problem: Svace reports a potential SIGN_EXTENSION issue in SplFixedArray::__serialize() in [ext/spl/spl_fixedarray.c](https://github.com/php/php-src/blob/c79284711bd8e610fb882bfdad48584b86fcdc62/ext/spl/spl_fixedarray.c#L603). The warning concerns the conversion of num_properties from uint32_t to zend_long in the expression intern->array.size + num_properties, which may cause different evaluation results on 32-bit and 64-bit platforms. However, num_properties is obtained from HashTable::nNumOfElements, and the maximum hash table size is limited by HT_MAX_SIZE (0x02000000 on 32-bit platforms and 0x40000000 on 64-bit platforms). The hash table implementation checks these limits when allocating and growing tables. If the number of elements cannot exceed the table capacity, num_properties remains below INT32_MAX on 32-bit platforms, preventing the sign-bit issue described by the warning. On 64-bit platforms, all uint32_t values are representable in int64_t. Request: Please confirm whether this warning can be classified as a false positive based on the HashTable size constraints and integer conversion rules. If nNumOfElements can exceed INT32_MAX on any supported 32-bit configuration, please clarify the conditions under which this can occur and whether additional validation is required. ### PHP Version ```plain PHP 8.3.31 (cli) ``` ### Operating System Ubuntu 24.04