Merge pull request #17 from AjaniBilby/dynamic-allocation-patch

[Bug] Large enough BNFs can cause memory overflow while compiling

docs/source/changelog.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Version 4.1.1
+
+### Fixes:
+  - [x] Fixed an issue where wasm memory usage exceeded predicted usage - the module now checks if it's about to run out of memory on the start of every rule being parsed.
+
 ## Version 4.1.0
 
 ### Added:

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "bnf-parser",
-	"version": "4.1.0",
+	"version": "4.1.1",
 	"description": "Deterministic BNF compiler/parser",
 	"homepage": "https://bnf-parser.ajanibilby.com",
 	"main": "./bin/index.js",

source/wasm/rule.ts

@@ -943,6 +943,34 @@ export function CompileRule(m: binaryen.Module, literals: LiteralMapping, rule:
 		ctx.m.block(null, [
 			ctx.m.local.set(error, ctx.m.i32.const(0)),
 
+			// Auto grow if 1kb from end of memory
+			ctx.m.if(
+				ctx.m.i32.lt_s(
+					ctx.m.i32.mul(
+						ctx.m.memory.size(),
+						ctx.m.i32.const(65_536) // bytes per page
+					),
+					ctx.m.i32.add(
+						ctx.m.global.get("heap", binaryen.i32),
+						ctx.m.i32.const(1024) // 1kb
+					)
+				),
+				ctx.m.block(null, [
+					rule.name === "expr_arg"
+						? ctx.m.call("print_i32", [
+							ctx.m.i32.sub(
+								ctx.m.i32.mul(
+									ctx.m.memory.size(),
+									ctx.m.i32.const(65_536) // bytes per page
+								),
+								ctx.m.global.get("heap", binaryen.i32)
+							)
+						], binaryen.none)
+						: ctx.m.nop(),
+					ctx.m.drop( ctx.m.memory.grow(ctx.m.i32.const(1)) )
+				])
+			),
+
 			innerWasm,
 
 			ctx.m.return(ctx.m.local.get(error, binaryen.i32))

test/bnf/long-syntax.bnf

@@ -0,0 +1,11 @@
+program ::= "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
+	"a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" ;
+
+# Remove a single "..." from this line and it will compile
+wordI ::= "b" "c" ;

test/sample/long-syntax/correct.txt

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa