Remove IS_STATIC_VAR_UNINITIALIZED

This flag was never necessary. We know a static variable is uninitialized (i.e.
the initializer has never been called) iff the zval in the static variable array
does not contain a reference.

Prompted by a related issue in ext-uopz reported by Christoph.

Author: iluuu1994

Zend/tests/static_variables_throwing_initializer.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Static variable with throwing initializer
+--FILE--
+<?php
+
+function foo($throw) {
+    static $a = $throw ? (throw new Exception('Throwing from foo()')) : 42;
+    return $a;
+}
+
+try {
+    var_dump(foo(true));
+} catch (Exception $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump(foo(false));
+
+?>
+--EXPECT--
+Throwing from foo()
+int(42)

Zend/zend_compile.c

@@ -5483,7 +5483,6 @@ static void zend_compile_static_var(zend_ast *ast) /* {{{ */
 		zend_op *opline;
 
 		zval *placeholder_ptr = zend_hash_update(CG(active_op_array)->static_variables, var_name, &EG(uninitialized_zval));
-		Z_TYPE_EXTRA_P(placeholder_ptr) |= IS_STATIC_VAR_UNINITIALIZED;
 		uint32_t placeholder_offset = (uint32_t)((char*)placeholder_ptr - (char*)CG(active_op_array)->static_variables->arData);
 
 		uint32_t static_def_jmp_opnum = get_next_op_number();

Zend/zend_types.h

@@ -791,11 +791,6 @@ static zend_always_inline uint32_t zval_gc_info(uint32_t gc_type_info) {
 /* zval.u1.v.type_flags */
 #define IS_TYPE_REFCOUNTED			(1<<0)
 #define IS_TYPE_COLLECTABLE			(1<<1)
-/* Used for static variables to check if they have been initialized. We can't use IS_UNDEF because
- * we can't store IS_UNDEF zvals in the static_variables HashTable. This needs to live in type_info
- * so that the ZEND_ASSIGN overrides it but is moved to extra to avoid breaking the Z_REFCOUNTED()
- * optimization that only checks for Z_TYPE_FLAGS() without `& (IS_TYPE_COLLECTABLE|IS_TYPE_REFCOUNTED)`. */
-#define IS_STATIC_VAR_UNINITIALIZED		(1<<0)
 
 #if 1
 /* This optimized version assumes that we have a single "type_flag" */

Zend/zend_vm_def.h

@@ -9110,7 +9110,7 @@ ZEND_VM_HANDLER(203, ZEND_BIND_INIT_STATIC_OR_JMP, CV, JMP_ADDR)
 	ZEND_ASSERT(GC_REFCOUNT(ht) == 1);
 
 	value = (zval*)((char*)ht->arData + opline->extended_value);
-	if (Z_TYPE_EXTRA_P(value) & IS_STATIC_VAR_UNINITIALIZED) {
+	if (Z_TYPE_P(value) == IS_NULL) {
 		ZEND_VM_NEXT_OPCODE();
 	} else {
 		SAVE_OPLINE();