[core/state] Mem alloc fix: Don't initialize sparse array with a long List[str] (#2268)

* [spec/ble-sparse] Add test case for `unset[-1]=1`
  * and fix bug
* [refactor core/bash_impl] Add "BashArray_New"

Author: akinomyoga

builtin/assign_osh.py

@@ -289,7 +289,7 @@ def _ReconcileTypes(rval, flag_a, flag_A, blame_word):
                 # mycpp limitation: NewDict() needs to be typed
                 tmp = NewDict()  # type: Dict[str, str]
                 return value.BashAssoc(tmp)
-                #return bash_impl.BashArray_FromList([])
+                #return bash_impl.BashArray_New()
 
         if rval.tag() != value_e.BashAssoc:
             e_usage("Got -A but RHS isn't an associative array",
@@ -323,7 +323,7 @@ def Run(self, cmd_val):
         for pair in cmd_val.pairs:
             if pair.rval is None:
                 if arg.a:
-                    rval = bash_impl.BashArray_FromList([])  # type: value_t
+                    rval = bash_impl.BashArray_New()  # type: value_t
                 elif arg.A:
                     # mycpp limitation: NewDict() needs to be typed
                     tmp = NewDict()  # type: Dict[str, str]
@@ -459,7 +459,7 @@ def Run(self, cmd_val):
                 if arg.a:
                     if old_val.tag() not in (value_e.InternalStringArray,
                                              value_e.BashArray):
-                        rval = bash_impl.BashArray_FromList([])
+                        rval = bash_impl.BashArray_New()
                 elif arg.A:
                     if old_val.tag() != value_e.BashAssoc:
                         # mycpp limitation: NewDict() needs to be typed

core/bash_impl.py

@@ -347,9 +347,15 @@ def BashAssoc_ToStrForShellPrint(assoc_val):
 # BashArray come here.
 
 
+def BashArray_New():
+    # type: () -> value.BashArray
+    d = {}  # type: Dict[mops.BigInt, str]
+    max_index = mops.MINUS_ONE  # max index for empty array
+    return value.BashArray(d, max_index)
+
+
 def BashArray_FromList(strs):
     # type: (List[str]) -> value.BashArray
-
     d = {}  # type: Dict[mops.BigInt, str]
     max_index = mops.MINUS_ONE  # max index for empty array
     for s in strs:

core/state.py

@@ -2004,7 +2004,8 @@ def SetValue(self, lval, val, which_scopes, flags=0):
                 cell, var_frame, _ = self._ResolveNameOrRef(
                     lval.name, which_scopes)
                 if not cell:
-                    self._BindNewArrayWithEntry(var_frame, lval, rval, flags)
+                    self._BindNewArrayWithEntry(var_frame, lval, rval, flags,
+                                                left_loc)
                     return
 
                 if cell.readonly:
@@ -2015,7 +2016,7 @@ def SetValue(self, lval, val, which_scopes, flags=0):
                 with tagswitch(UP_cell_val) as case2:
                     if case2(value_e.Undef):
                         self._BindNewArrayWithEntry(var_frame, lval, rval,
-                                                    flags)
+                                                    flags, left_loc)
                         return
 
                     elif case2(value_e.Str):
@@ -2076,13 +2077,16 @@ def SetValue(self, lval, val, which_scopes, flags=0):
             else:
                 raise AssertionError(lval.tag())
 
-    def _BindNewArrayWithEntry(self, var_frame, lval, val, flags):
-        # type: (Dict[str, Cell], sh_lvalue.Indexed, value.Str, int) -> None
+    def _BindNewArrayWithEntry(self, var_frame, lval, val, flags, blame_loc):
+        # type: (Dict[str, Cell], sh_lvalue.Indexed, value.Str, int, loc_t) -> None
         """Fill 'var_frame' with a new indexed array entry."""
-        no_str = None  # type: Optional[str]
-        items = [no_str] * lval.index
-        items.append(val.s)
-        new_value = bash_impl.BashArray_FromList(items)
+
+        new_value = bash_impl.BashArray_New()
+        error_code = bash_impl.BashArray_SetElement(new_value,
+                                                    mops.IntWiden(lval.index),
+                                                    val.s)
+        if error_code == error_code_e.IndexOutOfRange:
+            e_die("Index %d is out of bounds for array of length 0", blame_loc)
 
         # arrays can't be exported; can't have BashAssoc flag
         readonly = bool(flags & SetReadOnly)

spec/ble-sparse.test.sh

@@ -1181,3 +1181,23 @@ json write (crash_dump.var_stack[0].a)
 
 ## N-I bash/mksh STDOUT:
 ## END
+
+
+#### Regression: a[-1]=1
+case $SH in mksh) exit ;; esac
+
+a[-1]=1
+
+## status: 1
+## STDOUT:
+## END
+## STDERR:
+  a[-1]=1
+  ^~
+[ stdin ]:3: fatal: Index %d is out of bounds for array of length 0
+## END
+## OK bash STDERR:
+bash: line 3: a[-1]: bad array subscript
+## END
+## N-I mksh status: 0
+## N-I mksh stderr-json: ""