Allow negative string offsets.

Negative offsets return characters starting from the end of the string.
lt · Apr 17, 2014 · 8bfd09b · 8bfd09b
1 parent a381cc3
commit 8bfd09b
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Showing 2 changed files with 18 additions and 2 deletions.
diff --git a/Zend/zend_execute.c b/Zend/zend_execute.c
@@ -1300,15 +1300,20 @@ static void zend_fetch_dimension_address_read(temp_variable *result, zval *conta
 				INIT_PZVAL(ptr);
 				Z_TYPE_P(ptr) = IS_STRING;
 
-				if (Z_LVAL_P(dim) < 0 || Z_STRLEN_P(container) <= Z_LVAL_P(dim)) {
+				if (Z_STRLEN_P(container) <= Z_LVAL_P(dim) || (Z_LVAL_P(dim) < 0 && Z_LVAL_P(dim) < -Z_STRLEN_P(container))) {
 					if (type != BP_VAR_IS) {
 						zend_error(E_NOTICE, "Uninitialized string offset: %ld", Z_LVAL_P(dim));
 					}
 					Z_STRVAL_P(ptr) = STR_EMPTY_ALLOC();
 					Z_STRLEN_P(ptr) = 0;
 				} else {
 					Z_STRVAL_P(ptr) = (char*)emalloc(2);
-					Z_STRVAL_P(ptr)[0] = Z_STRVAL_P(container)[Z_LVAL_P(dim)];
+					if (Z_LVAL_P(dim) < 0) {
+						Z_STRVAL_P(ptr)[0] = Z_STRVAL_P(container)[Z_STRLEN_P(container) + Z_LVAL_P(dim)];
+					}
+					else {
+						Z_STRVAL_P(ptr)[0] = Z_STRVAL_P(container)[Z_LVAL_P(dim)];
+					}
 					Z_STRVAL_P(ptr)[1] = 0;
 					Z_STRLEN_P(ptr) = 1;
 				}

diff --git a/tests/strings/offsets_general.phpt b/tests/strings/offsets_general.phpt
@@ -17,6 +17,10 @@ var_dump(isset($string{0}));
 var_dump(isset($string{0}{0}));
 var_dump($string{"foo"});
 var_dump(isset($string{"foo"}{"bar"}));
+var_dump($string[6]);
+var_dump($string[-1]);
+var_dump($string[-6]);
+var_dump($string[-7]);
 ?>
 --EXPECTF--
 string(1) "f"
@@ -36,3 +40,10 @@ Warning: Illegal string offset 'foo' in %s line %d
 string(1) "f"
 bool(false)
 
+Notice: Uninitialized string offset: %d in %s line %d
+string(0) ""
+string(1) "r"
+string(1) "f"
+
+Notice: Uninitialized string offset: -%d in %s line %d
+string(0) ""