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GH-927: Fix circumvention of evaluation order in 'when' conditions

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Historically, a 'when' condition performed an AST-traversal to locate
any index-expressions like `x[9]` and evaluated them so that it could
register the associated value as something for which it needs to receive
"modification" notifications.

Evaluating arbitrary expressions during an AST-traversal like that ignores
the typical order-of-evaluation/short-circuiting you'd expect if the
condition was evaluated normally, from its root expression.

Now, a new subclass of IndexExpr is used to keep track of all IndexExpr
results in the context of evaluating a 'when' condition without having
to do a secondary AST-traversal-and-eval.  i.e. the first evaluation of
the full 'when' condition follows the typical expression-evaluation
semantics (as always), but additionally now captures all the values
a Trigger needs to monitor for modifications.
This commit is contained in:
Jon Siwek 2020-09-15 16:50:24 -07:00
parent 0771dbcec6
commit 33ca675515
6 changed files with 141 additions and 29 deletions
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27
src/parse.y
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@ -58,7 +58,7 @@
%type <ic> init_class
%type <expr> opt_init
%type <val> TOK_CONSTANT
%type <expr> expr opt_expr init anonymous_function lambda_body index_slice opt_deprecated
%type <expr> expr opt_expr init anonymous_function lambda_body index_slice opt_deprecated when_condition
%type <event_expr> event
%type <stmt> stmt stmt_list func_body for_head
%type <type> type opt_type enum_body
@ -126,6 +126,7 @@ extern zeek::detail::Expr* g_curr_debug_expr;
extern bool in_debug;
extern const char* g_curr_debug_error;
static int in_when_cond = 0;
static int in_hook = 0;
int in_init = 0;
int in_record = 0;
@ -289,6 +290,11 @@ opt_expr:
{ $$ = 0; }
;
when_condition:
{ ++in_when_cond; } expr { --in_when_cond; }
{ $$ = $2; }
;
expr:
'(' expr ')'
{
@ -474,7 +480,10 @@ expr:
| expr '[' expr_list ']'
{
zeek::detail::set_location(@1, @4);
$$ = new zeek::detail::IndexExpr({zeek::AdoptRef{}, $1}, {zeek::AdoptRef{}, $3});
if ( in_when_cond > 0 )
$$ = new zeek::detail::IndexExprWhen({zeek::AdoptRef{}, $1}, {zeek::AdoptRef{}, $3});
else
$$ = new zeek::detail::IndexExpr({zeek::AdoptRef{}, $1}, {zeek::AdoptRef{}, $3});
}
| index_slice
@ -1328,7 +1337,11 @@ index_slice:
auto le = zeek::make_intrusive<zeek::detail::ListExpr>(std::move(low));
le->Append(std::move(high));
$$ = new zeek::detail::IndexExpr({zeek::AdoptRef{}, $1}, std::move(le), true);
if ( in_when_cond > 0 )
$$ = new zeek::detail::IndexExprWhen({zeek::AdoptRef{}, $1}, std::move(le), true);
else
$$ = new zeek::detail::IndexExpr({zeek::AdoptRef{}, $1}, std::move(le), true);
}
opt_attr:
@ -1535,14 +1548,14 @@ stmt:
zeek::detail::script_coverage_mgr.AddStmt($$);
}
| TOK_WHEN '(' expr ')' stmt
| TOK_WHEN '(' when_condition ')' stmt
{
zeek::detail::set_location(@3, @5);
$$ = new zeek::detail::WhenStmt({zeek::AdoptRef{}, $3}, {zeek::AdoptRef{}, $5},
nullptr, nullptr, false);
}
| TOK_WHEN '(' expr ')' stmt TOK_TIMEOUT expr '{' opt_no_test_block stmt_list '}'
| TOK_WHEN '(' when_condition ')' stmt TOK_TIMEOUT expr '{' opt_no_test_block stmt_list '}'
{
zeek::detail::set_location(@3, @9);
$$ = new zeek::detail::WhenStmt({zeek::AdoptRef{}, $3}, {zeek::AdoptRef{}, $5},
@ -1552,14 +1565,14 @@ stmt:
}
| TOK_RETURN TOK_WHEN '(' expr ')' stmt
| TOK_RETURN TOK_WHEN '(' when_condition ')' stmt
{
zeek::detail::set_location(@4, @6);
$$ = new zeek::detail::WhenStmt({zeek::AdoptRef{}, $4}, {zeek::AdoptRef{}, $6}, nullptr,
nullptr, true);
}
| TOK_RETURN TOK_WHEN '(' expr ')' stmt TOK_TIMEOUT expr '{' opt_no_test_block stmt_list '}'
| TOK_RETURN TOK_WHEN '(' when_condition ')' stmt TOK_TIMEOUT expr '{' opt_no_test_block stmt_list '}'
{
zeek::detail::set_location(@4, @10);
$$ = new zeek::detail::WhenStmt({zeek::AdoptRef{}, $4}, {zeek::AdoptRef{}, $6},