V8 crashes when trying to parse a list

[tornikeshavishvili]

Hello

V8 crashes when trying to use following grammar:

test 'test'
 = ss:'aa'|1..8,((_+'.'_+)/(_+','_+))|{
 return ss
}

_ "whitespace"
  = [ \t\n\r]* {
    return ''
  }

my node: v18.7.0
chrome: Version 110.0.5481.177 (Official Build) (64-bit)

I suspect that crash happens upon successful mach.

@Mingun

[Mingun]

The reason in that _+ creates an infinity parse loop, because _ is always matched (because it could match empty input). You should change the _ definition:

 _ "whitespace"
-  = [ \t\n\r]* {
+  = [ \t\n\r] {
     return ''
   }

It seems an oversight from my side. We should run check(node.delimiter) somewhere here:

peggy/lib/compiler/passes/report-infinite-repetition.js

Lines 28 to 53 in 00855f6

	repeated(node) {
	if (asts.alwaysConsumesOnSuccess(ast, node.expression)
	|| node.delimiter && asts.alwaysConsumesOnSuccess(ast, node.delimiter)
	) {
	return;
	}
	if (node.max.value === null) {
	session.error(
	"Possible infinite loop when parsing (unbounded range repetition used with an expression that may not consume any input)",
	node.location
	);
	} else {
	// If minimum is `null` it is equals to maximum (parsed from `|exact|` syntax)
	const min = node.min ? node.min : node.max;
	// Because the high boundary is defined, infinity repetition is not possible
	// but the grammar will waste of CPU
	session.warning(
	min.type === "constant" && node.max.type === "constant"
	? `An expression may not consume any input and may always match ${node.max.value} times`
	: "An expression may not consume any input and may always match with a maximum repetition count",
	node.location
	);
	}
	},
	});

[hildjj]

Can we get this into a 3.0.1 release in the next day or two, or should I go ahead without it?

[tornikeshavishvili]

I want to have a look as soon as possible on provided code, but . . . i have difficulties to understand what is written and why :(((

[hildjj]

@Mingun I'd like to get this fixed before the release, if you have the time.

[hildjj]

I've got it. When I tried it the first time, I put the check in the wrong place. Adding tests now.