fix GH-7899 Regression in unpack for negative int value

Author: remicollet

NEWS

@@ -16,6 +16,9 @@ PHP                                                                        NEWS
 - pcntl:
   . Fixed pcntl_rfork build for DragonFlyBSD. (David Carlier)
 
+- Standard:
+  . Fixed bug GH-7899 (Regression in unpack for negative int value). (Remi)
+
 06 Jan 2022, PHP 8.1.2RC1
 
 - Core:

ext/standard/pack.c

@@ -62,6 +62,7 @@ typedef ZEND_SET_ALIGNED(1, uint16_t unaligned_uint16_t);
 typedef ZEND_SET_ALIGNED(1, uint32_t unaligned_uint32_t);
 typedef ZEND_SET_ALIGNED(1, uint64_t unaligned_uint64_t);
 typedef ZEND_SET_ALIGNED(1, unsigned int unaligned_uint);
+typedef ZEND_SET_ALIGNED(1, int unaligned_int);
 
 /* Mapping of byte from char (8bit) to long for machine endian */
 static int byte_map[1];
@@ -1043,8 +1044,14 @@ PHP_FUNCTION(unpack)
 
 					case 'i':   /* signed integer, machine size, machine endian */
 					case 'I': { /* unsigned integer, machine size, machine endian */
-						unsigned int x = *((unaligned_uint*) &input[inputpos]);
-						zend_long v = (type == 'i') ? (int) x : x;
+						zend_long v;
+						if (type == 'i') {
+							int x = *((unaligned_int*) &input[inputpos]);
+							v = x;
+						} else {
+							unsigned int x = *((unaligned_uint*) &input[inputpos]);
+							v = x;
+						}
 
 						ZVAL_LONG(&val, v);
 						zend_symtable_update(Z_ARRVAL_P(return_value), real_name, &val);

ext/standard/tests/strings/pack64.phpt

@@ -31,6 +31,11 @@ print_r(unpack("q", pack("q", 0)));
 print_r(unpack("q", pack("q", 0x8000000000000002)));
 print_r(unpack("q", pack("q", -1)));
 print_r(unpack("q", pack("q", 0x8000000000000000)));
+
+print_r(unpack("i", pack("i",  2147483647))); // Max int32
+print_r(unpack("i", pack("i", -2147483647)));
+print_r(unpack("i", pack("i", -2147483648))); // Min int32
+print_r(unpack("I", pack("I",  4294967295))); // Max uint32
 ?>
 --EXPECT--
 Array
@@ -113,3 +118,19 @@ Array
 (
     [1] => -9223372036854775808
 )
+Array
+(
+    [1] => 2147483647
+)
+Array
+(
+    [1] => -2147483647
+)
+Array
+(
+    [1] => -2147483648
+)
+Array
+(
+    [1] => 4294967295
+)