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Fix memory leak in vector slice assignment

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Two parts to this:

  * Only allow vector slice assignment in statement contexts, not in
    arbitrary assignment expressions.  E.g. it's not clear what the
    resulting value of `(v[1:2] = vector(1))` is for further expression
    chaining.  For reference, Python doesn't allow it either.

  * Add a subclass of AssignExpr to specialize the behavior for index
    slice assignments (because its behavior regarding expression
    chaining is different per the previous point) and Unref the RHS
    of things like `v[1:2] = vector(1)` after IndexExpr::Assign is
    finished inserting it (since no one else takes ownership of it).

Instead of using an Expr subclass, IndexSliceAssignExpr, we could
use a proper Stmt, since that's the only context we currently use it
for, but if we did ever to decide on allowing its use in arbitrary
expression contexts, then I expect we'll need it this way anyway
(just with a different IndexSliceAssignExpr::Eval implementation).
This commit is contained in:
Jon Siwek 2019-06-18 17:42:06 -07:00
parent 91835752b7
commit 385f500497
5 changed files with 140 additions and 21 deletions
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48
src/parse.y
View file

@ -5,7 +5,7 @@
// Switching parser table type fixes ambiguity problems.
%define lr.type ielr
%expect 103
%expect 104
%token TOK_ADD TOK_ADD_TO TOK_ADDR TOK_ANY
%token TOK_ATENDIF TOK_ATELSE TOK_ATIF TOK_ATIFDEF TOK_ATIFNDEF
@ -57,7 +57,7 @@
%type <ic> init_class
%type <expr> opt_init
%type <val> TOK_CONSTANT
%type <expr> expr opt_expr init anonymous_function
%type <expr> expr opt_expr init anonymous_function index_slice
%type <event_expr> event
%type <stmt> stmt stmt_list func_body for_head
%type <type> type opt_type enum_body
@ -464,6 +464,12 @@ expr:
| expr '=' expr
{
set_location(@1, @3);
if ( $1->Tag() == EXPR_INDEX && $1->AsIndexExpr()->IsSlice() )
reporter->Error("index slice assignment may not be used"
" in arbitrary expression contexts, only"
" as a statement");
$$ = get_assign_expr($1, $3, in_init);
}
@ -479,19 +485,7 @@ expr:
$$ = new IndexExpr($1, $3);
}
| expr '[' opt_expr ':' opt_expr ']'
{
set_location(@1, @6);
Expr* low = $3 ? $3 : new ConstExpr(val_mgr->GetCount(0));
Expr* high = $5 ? $5 : new SizeExpr($1);
if ( ! IsIntegral(low->Type()->Tag()) || ! IsIntegral(high->Type()->Tag()) )
reporter->Error("slice notation must have integral values as indexes");
ListExpr* le = new ListExpr(low);
le->Append(high);
$$ = new IndexExpr($1, le, true);
}
| index_slice
| expr '$' TOK_ID
{
@ -1271,6 +1265,21 @@ init:
| expr
;
index_slice:
expr '[' opt_expr ':' opt_expr ']'
{
set_location(@1, @6);
Expr* low = $3 ? $3 : new ConstExpr(val_mgr->GetCount(0));
Expr* high = $5 ? $5 : new SizeExpr($1);
if ( ! IsIntegral(low->Type()->Tag()) || ! IsIntegral(high->Type()->Tag()) )
reporter->Error("slice notation must have integral values as indexes");
ListExpr* le = new ListExpr(low);
le->Append(high);
$$ = new IndexExpr($1, le, true);
}
opt_attr:
attr_list
|
@ -1474,6 +1483,15 @@ stmt:
brofiler.DecIgnoreDepth();
}
| index_slice '=' expr ';' opt_no_test
{
set_location(@1, @4);
$$ = new ExprStmt(get_assign_expr($1, $3, in_init));
if ( ! $5 )
brofiler.AddStmt($$);
}
| expr ';' opt_no_test
{
set_location(@1, @2);