Fix GH-19300: Nested array_multisort invocation with error breaks

There are 2 issues:
1. When a MULTISORT_ABORT happens, it frees func, but func may point to
   ARRAYG(multisort_func), which would be a problem with nested
   invocations as it can destroy that of the "parent" invocation.
   To solve this, delay assigning to the globals.
2. The old globals were not restored which means that nested invocations
   with different flags will cause a wrong sorting function to be used.

Author: ndossche

ext/standard/array.c

@@ -5911,7 +5911,7 @@ PHP_FUNCTION(array_multisort)
 	for (i = 0; i < MULTISORT_LAST; i++) {
 		parse_state[i] = 0;
 	}
-	func = ARRAYG(multisort_func) = ecalloc(argc, sizeof(bucket_compare_func_t));
+	func = ecalloc(argc, sizeof(bucket_compare_func_t));
 
 	/* Here we go through the input arguments and parse them. Each one can
 	 * be either an array or a sort flag which follows an array. If not
@@ -5927,7 +5927,7 @@ PHP_FUNCTION(array_multisort)
 			/* We see the next array, so we update the sort flags of
 			 * the previous array and reset the sort flags. */
 			if (i > 0) {
-				ARRAYG(multisort_func)[num_arrays - 1] = php_get_data_compare_func_unstable(sort_type, sort_order != PHP_SORT_ASC);
+				func[num_arrays - 1] = php_get_data_compare_func_unstable(sort_type, sort_order != PHP_SORT_ASC);
 				sort_order = PHP_SORT_ASC;
 				sort_type = PHP_SORT_REGULAR;
 			}
@@ -5979,8 +5979,6 @@ PHP_FUNCTION(array_multisort)
 			MULTISORT_ABORT;
 		}
 	}
-	/* Take care of the last array sort flags. */
-	ARRAYG(multisort_func)[num_arrays - 1] = php_get_data_compare_func_unstable(sort_type, sort_order != PHP_SORT_ASC);
 
 	/* Make sure the arrays are of the same size. */
 	array_size = zend_hash_num_elements(Z_ARRVAL_P(arrays[0]));
@@ -5998,6 +5996,11 @@ PHP_FUNCTION(array_multisort)
 		RETURN_TRUE;
 	}
 
+	/* Take care of the last array sort flags. */
+	func[num_arrays - 1] = php_get_data_compare_func_unstable(sort_type, sort_order != PHP_SORT_ASC);
+	bucket_compare_func_t *old_multisort_func = ARRAYG(multisort_func);
+	ARRAYG(multisort_func) = func;
+
 	/* Create the indirection array. This array is of size MxN, where
 	 * M is the number of entries in each input array and N is the number
 	 * of the input arrays + 1. The last column is UNDEF to indicate the end
@@ -6074,6 +6077,7 @@ PHP_FUNCTION(array_multisort)
 	efree(indirect);
 	efree(func);
 	efree(arrays);
+	ARRAYG(multisort_func) = old_multisort_func;
 }
 /* }}} */
 

ext/standard/tests/array/gh19300_1.phpt

@@ -0,0 +1,40 @@
+--TEST--
+GH-19300 (Nested array_multisort invocation with error breaks) - correct invocation variation
+--FILE--
+<?php
+class MyStringable {
+    public function __construct(private string $data) {}
+    public function __tostring() {
+        array_multisort([]); // Trigger update of array sort globals in happy path
+        return $this->data;
+    }
+}
+
+$inputs = [
+    new MyStringable('3'),
+    new MyStringable('1'),
+    new MyStringable('2'),
+];
+
+var_dump(array_multisort($inputs, SORT_STRING));
+var_dump($inputs);
+?>
+--EXPECT--
+bool(true)
+array(3) {
+  [0]=>
+  object(MyStringable)#2 (1) {
+    ["data":"MyStringable":private]=>
+    string(1) "1"
+  }
+  [1]=>
+  object(MyStringable)#3 (1) {
+    ["data":"MyStringable":private]=>
+    string(1) "2"
+  }
+  [2]=>
+  object(MyStringable)#1 (1) {
+    ["data":"MyStringable":private]=>
+    string(1) "3"
+  }
+}

ext/standard/tests/array/gh19300_2.phpt

@@ -0,0 +1,40 @@
+--TEST--
+GH-19300 (Nested array_multisort invocation with error breaks) - error variation
+--FILE--
+<?php
+
+function error_handle($level, $message, $file = '', $line = 0){
+    try {
+        array_multisort($a, SORT_ASC); // Trigger multisort abort
+    } catch (TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+set_error_handler('error_handle');
+
+$inputs = [
+    new stdClass,
+    new stdClass,
+    new stdClass,
+];
+
+var_dump(array_multisort($inputs, SORT_NUMERIC));
+var_dump($inputs);
+?>
+--EXPECT--
+array_multisort(): Argument #1 ($array) must be an array or a sort flag
+array_multisort(): Argument #1 ($array) must be an array or a sort flag
+array_multisort(): Argument #1 ($array) must be an array or a sort flag
+array_multisort(): Argument #1 ($array) must be an array or a sort flag
+bool(true)
+array(3) {
+  [0]=>
+  object(stdClass)#1 (0) {
+  }
+  [1]=>
+  object(stdClass)#2 (0) {
+  }
+  [2]=>
+  object(stdClass)#3 (0) {
+  }
+}