Replace ZEND_ASSUME() by ZEND_ASSERT() in zend_hash_*_ptr setters

[TimWolla]

I had a case where I was intentionally storing a NULL pointer within a HashTable to mark an entry as “blocked”, without paying for the overhead of checking the entry type when reading the pointer, resulting in semantics that are similar to using isset() instead of array_key_exists() in userland.

This worked fine in unoptimized test builds, but due to the ZEND_ASSUME() in the zend_hash_find_ptr functions, the optimized release builds turned the logic of:

my_pointer = zend_hash_find_ptr(ht, key);
if (my_pointer == NULL) {
    return;
}
*my_pointer;

into

zv = zend_hash_find(ht, key);
if (zv) {
    *Z_PTR_P(zv);
} else {
    return;
}

thus introducing a hard-to-debug and compiler-dependent crash when the entry exists, but the stored pointer is NULL.

Change the ZEND_ASSUME() in the setters to ZEND_ASSERT(). This would have made my mistake immediately obvious in debug builds when storing the pointer. The getters still use ZEND_ASSUME() under the assumption that they are called much more often, reducing the impact on debug builds: Assuming the developer uses the _ptr variants for both reading and writing the entries, the mistake will be reliably caught during writing, making the assert during reading unnecessary.

For release builds the ZEND_ASSERT() will be equivalent to ZEND_ASSUME(), avoiding any performance impact for those.

[dstogov]

This shouldn't make any problems.