core: Warn when coercing NAN to other types

RFC: https://wiki.php.net/rfc/warnings-php-8-5#coercing_nan_to_other_types

Author: Girgias

Zend/Optimizer/block_pass.c

@@ -436,21 +436,14 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
 					Tsource[VAR_NUM(opline->op1.var)] = NULL;
 					break;
 				}
-				ZEND_FALLTHROUGH;
-
-			case ZEND_IS_EQUAL:
-			case ZEND_IS_NOT_EQUAL:
 				if (opline->op1_type == IS_CONST &&
-				    opline->op2_type == IS_CONST) {
+					opline->op2_type == IS_CONST) {
 					goto optimize_constant_binary_op;
-				}
-		        /* IS_EQ(TRUE, X)      => BOOL(X)
-		         * IS_EQ(FALSE, X)     => BOOL_NOT(X)
-		         * IS_NOT_EQ(TRUE, X)  => BOOL_NOT(X)
-		         * IS_NOT_EQ(FALSE, X) => BOOL(X)
-		         * CASE(TRUE, X)       => BOOL(X)
-		         * CASE(FALSE, X)      => BOOL_NOT(X)
-		         */
+					}
+				/*
+				 * CASE(TRUE, X)       => BOOL(X)
+				 * CASE(FALSE, X)      => BOOL_NOT(X)
+				 */
 				if (opline->op1_type == IS_CONST &&
 					(Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_FALSE ||
 					 Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_TRUE)) {
@@ -464,19 +457,34 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
 					SET_UNUSED(opline->op2);
 					++(*opt_count);
 					goto optimize_bool;
-				} else if (opline->op2_type == IS_CONST &&
-				           (Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_FALSE ||
-				            Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_TRUE)) {
-					/* Optimization of comparison with "null" is not safe,
-					 * because ("0" == null) is not equal to !("0")
-					 */
-					opline->opcode =
-						((opline->opcode != ZEND_IS_NOT_EQUAL) == ((Z_TYPE(ZEND_OP2_LITERAL(opline))) == IS_TRUE)) ?
-						ZEND_BOOL : ZEND_BOOL_NOT;
-					SET_UNUSED(opline->op2);
-					++(*opt_count);
-					goto optimize_bool;
+					 } else if (opline->op2_type == IS_CONST &&
+								(Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_FALSE ||
+								 Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_TRUE)) {
+					 	/* Optimization of comparison with "null" is not safe,
+						  * because ("0" == null) is not equal to !("0")
+						  */
+					 	opline->opcode =
+							 ((opline->opcode != ZEND_IS_NOT_EQUAL) == ((Z_TYPE(ZEND_OP2_LITERAL(opline))) == IS_TRUE)) ?
+							 ZEND_BOOL : ZEND_BOOL_NOT;
+					 	SET_UNUSED(opline->op2);
+					 	++(*opt_count);
+					 	goto optimize_bool;
+								 }
+				break;
+
+			case ZEND_IS_EQUAL:
+			case ZEND_IS_NOT_EQUAL:
+				if (opline->op1_type == IS_CONST &&
+				    opline->op2_type == IS_CONST) {
+					goto optimize_constant_binary_op;
 				}
+				/* IS_EQ(TRUE, X)      => BOOL(X)
+				 * IS_EQ(FALSE, X)     => BOOL_NOT(X)
+				 * IS_NOT_EQ(TRUE, X)  => BOOL_NOT(X)
+				 * IS_NOT_EQ(FALSE, X) => BOOL(X)
+				 * Those optimizations are not safe if the other operand end up being NAN
+				 * as BOOL/BOOL_NOT will warn which IS_EQUAL/IS_NOT_EQUAL do not.
+				 */
 				break;
 			case ZEND_IS_IDENTICAL:
 				if (opline->op1_type == IS_CONST &&

Zend/Optimizer/sccp.c

@@ -335,6 +335,10 @@ static inline zend_result ct_eval_bool_cast(zval *result, zval *op) {
 		ZVAL_TRUE(result);
 		return SUCCESS;
 	}
+	/* NAN warns when casting */
+	if (Z_TYPE_P(op) == IS_DOUBLE && zend_isnan(Z_DVAL_P(op))) {
+		return FAILURE;
+	}
 
 	ZVAL_BOOL(result, zend_is_true(op));
 	return SUCCESS;

Zend/Optimizer/zend_inference.c

@@ -5109,14 +5109,16 @@ ZEND_API bool zend_may_throw_ex(const zend_op *opline, const zend_ssa_op *ssa_op
 		case ZEND_PRE_DEC:
 		case ZEND_POST_DEC:
 			return (t1 & (MAY_BE_NULL|MAY_BE_FALSE|MAY_BE_TRUE|MAY_BE_STRING|MAY_BE_ARRAY|MAY_BE_OBJECT|MAY_BE_RESOURCE));
-		case ZEND_BOOL_NOT:
 		case ZEND_JMPZ:
 		case ZEND_JMPNZ:
 		case ZEND_JMPZ_EX:
 		case ZEND_JMPNZ_EX:
-		case ZEND_BOOL:
 		case ZEND_JMP_SET:
 			return (t1 & MAY_BE_OBJECT);
+		case ZEND_BOOL:
+		case ZEND_BOOL_NOT:
+			/* NAN Cast to bool will warn */
+			return (t1 & MAY_BE_OBJECT) || (t1 & MAY_BE_DOUBLE);
 		case ZEND_BOOL_XOR:
 			return (t1 & MAY_BE_OBJECT) || (t2 & MAY_BE_OBJECT);
 		case ZEND_IS_EQUAL:

Zend/Optimizer/zend_optimizer.c

@@ -74,6 +74,9 @@ zend_result zend_optimizer_eval_unary_op(zval *result, uint8_t opcode, zval *op1
 		}
 		return unary_op(result, op1);
 	} else { /* ZEND_BOOL */
+		if (Z_TYPE_P(op1) == IS_DOUBLE && zend_isnan(Z_DVAL_P(op1))) {
+			return FAILURE;
+		}
 		ZVAL_BOOL(result, zend_is_true(op1));
 		return SUCCESS;
 	}

Zend/tests/optimizer/nan_warning_switch.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Checking NAN in a switch statement with true/false
+--FILE--
+<?php
+
+$nan = fdiv(0, 0);
+switch ($nan) {
+    case true:
+        echo "true";
+        break;
+    case false:
+        echo "false";
+        break;
+}
+?>
+--EXPECT--
+true

Zend/tests/type_coercion/float_to_int/explicit_casts_should_not_warn.phpt

@@ -26,6 +26,7 @@ foreach($values as $value) {
 
 ?>
 --EXPECTF--
+Warning: unexpected NAN value was coerced to string in %s on line %d
 int(3)
 int(3)
 

Zend/tests/type_coercion/float_to_int/explicit_casts_should_not_warn_32bit.phpt

@@ -1,5 +1,5 @@
 --TEST--
-Explicit (int) cast must not warn 32bit variation
+Explicit (int) cast must not warn if value is representable 32bit variation
 --SKIPIF--
 <?php
 if (PHP_INT_SIZE != 4) die("skip this test is for 32bit platform only");
@@ -26,6 +26,7 @@ foreach($values as $value) {
 
 ?>
 --EXPECTF--
+Warning: unexpected NAN value was coerced to string in %s on line %d
 int(3)
 int(3)
 

Zend/tests/type_coercion/float_to_int/union_int_string_type_arg.phpt

@@ -23,6 +23,8 @@ int(1)
 
 Deprecated: Implicit conversion from float 1.5 to int loses precision in %s on line %d
 int(1)
+
+Warning: unexpected NAN value was coerced to string in %s on line %d
 string(3) "NAN"
 string(8) "1.0E+121"
 string(3) "INF"

Zend/tests/type_coercion/nan_to_other.phpt

@@ -40,31 +40,53 @@ foreach ($types as $type) {
 ?>
 --EXPECTF--
 float(NAN)
+
+Warning: unexpected NAN value was coerced to bool in %s on line %d
 bool(true)
+
+Warning: unexpected NAN value was coerced to string in %s on line %d
 string(3) "NAN"
 
 Warning: The float NAN is not representable as an int, cast occurred in %s on line %d
 int(0)
+
+Warning: unexpected NAN value was coerced to bool in %s on line %d
 bool(true)
+
+Warning: unexpected NAN value was coerced to string in %s on line %d
 string(3) "NAN"
+
+Warning: unexpected NAN value was coerced to array in %s on line %d
 array(1) {
   [0]=>
   float(NAN)
 }
+
+Warning: unexpected NAN value was coerced to object in %s on line %d
 object(stdClass)#%d (1) {
   ["scalar"]=>
   float(NAN)
 }
+
+Warning: unexpected NAN value was coerced to null in %s on line %d
 NULL
+
+Warning: unexpected NAN value was coerced to bool in %s on line %d
 bool(true)
 
 Warning: The float NAN is not representable as an int, cast occurred in %s on line %d
 int(0)
+
+Warning: unexpected NAN value was coerced to string in %s on line %d
 string(3) "NAN"
+
+Warning: unexpected NAN value was coerced to array in %s on line %d
 array(1) {
   [0]=>
   float(NAN)
 }
+
+Warning: unexpected NAN value was coerced to object in %s on line %d
 object(stdClass)#%d (1) {
   ["scalar"]=>
   float(NAN)

Zend/tests/type_declarations/scalar_basic.phpt

@@ -194,6 +194,7 @@ string(0) ""
 string(%d) "%d"
 
 *** Trying float(NAN)
+E_WARNING: unexpected NAN value was coerced to string on line %d
 string(3) "NAN"
 
 *** Trying bool(true)
@@ -247,6 +248,7 @@ bool(false)
 bool(true)
 
 *** Trying float(NAN)
+E_WARNING: unexpected NAN value was coerced to bool on line %d
 bool(true)
 
 *** Trying bool(true)