Bug 906963 - Detect whether a bytecode offset is within the scope of a catch statement.

js/src/jit-test/tests/debug/Script-isInCatchScope.js

@@ -0,0 +1,64 @@
+// Test if isInCatchScope properly detects catch blocks.
+
+let g = newGlobal('new-compartment');
+let dbg = new Debugger(g);
+
+function test(string, mustBeCaught) {
+    let index = 0;
+    dbg.onExceptionUnwind = function (frame) {
+        let willBeCaught = false;
+        do {
+            if (frame.script.isInCatchScope(frame.offset)) {
+                willBeCaught = true;
+                break;
+            }
+            frame = frame.older;
+        } while (frame != null);
+        assertEq(willBeCaught, mustBeCaught[index++]);
+    };
+
+    try {
+        g.eval(string);
+    } catch (ex) {}
+    assertEq(index, mustBeCaught.length);
+}
+
+// Should correctly detect catch blocks
+test("throw new Error();", [false]);
+test("try { throw new Error(); } catch (e) {}", [true]);
+test("try { throw new Error(); } finally {}", [false, false]);
+test("try { throw new Error(); } catch (e) {} finally {}", [true]);
+
+// Source of the exception shouldn't matter
+test("(null)();", [false]);
+test("try { (null)(); } catch (e) {}", [true]);
+test("try { (null)(); } finally {}", [false, false]);
+test("try { (null)(); } catch (e) {} finally {}", [true]);
+
+// Should correctly detect catch blocks in functions
+test("function f() { throw new Error(); } f();", [false, false]);
+test("function f() { try { throw new Error(); } catch (e) {} } f();", [true]);
+test("function f() { try { throw new Error(); } finally {} } f();", [false, false, false]);
+test("function f() { try { throw new Error(); } catch (e) {} finally {} } f();", [true]);
+
+// Should correctly detect catch blocks in evals
+test("eval('throw new Error();')", [false, false]);
+test("eval('try { throw new Error(); } catch (e) {}');", [true]);
+test("eval('try { throw new Error(); } finally {}');", [false, false, false]);
+test("eval('try { throw new Error(); } catch (e) {} finally {}');", [true]);
+
+// Should correctly detect rethrows
+test("try { throw new Error(); } catch (e) { throw e; }", [true, false]);
+test("try { try { throw new Error(); } catch (e) { throw e; } } catch (e) {}", [true, true]);
+test("try { try { throw new Error(); } finally {} } catch (e) {}", [true, true]);
+test("function f() { try { throw new Error(); } catch (e) { throw e; } } f();", [true, false, false]);
+test("function f() { try { try { throw new Error(); } catch (e) { throw e; } } catch (e) {} } f();", [true, true]);
+test("function f() { try { try { throw new Error(); } finally {} } catch (e) {} } f();", [true, true]);
+test("eval('try { throw new Error(); } catch (e) { throw e; }')", [true, false, false]);
+test("eval('try { try { throw new Error(); } catch (e) { throw e; } } catch (e) {}')", [true, true]);
+
+// Should correctly detect catch blocks across frame boundaries
+test("function f() { throw new Error(); } try { f(); } catch (e) {}", [true, true]);
+test("function f() { throw new Error(); } try { f(); } catch (e) { throw e; }", [true, true, false]);
+test("try { eval('throw new Error()'); } catch (e) {}", [true, true]);
+test("try { eval('throw new Error()'); } catch (e) { throw e; }", [true, true, false]);

js/src/vm/Debugger.cpp

@@ -3517,6 +3517,39 @@ DebuggerScript_clearAllBreakpoints(JSContext *cx, unsigned argc, Value *vp)
     return true;
 }
 
+static bool
+DebuggerScript_isInCatchScope(JSContext *cx, unsigned argc, Value* vp)
+{
+    REQUIRE_ARGC("Debugger.Script.isInCatchScope", 1);
+    THIS_DEBUGSCRIPT_SCRIPT(cx, argc, vp, "isInCatchScope", args, obj, script);
+
+    size_t offset;
+    if (!ScriptOffset(cx, script, args[0], &offset))
+        return false;
+
+    /*
+     * Try note ranges are relative to the mainOffset of the script, so adjust
+     * offset accordingly.
+     */
+    offset -= script->mainOffset;
+
+    args.rval().setBoolean(false);
+    if (script->hasTrynotes()) {
+        JSTryNote* tnBegin = script->trynotes()->vector;
+        JSTryNote* tnEnd = tnBegin + script->trynotes()->length;
+        while (tnBegin != tnEnd) {
+            if (offset - tnBegin->start < tnBegin->length &&
+                tnBegin->kind == JSTRY_CATCH)
+            {
+                args.rval().setBoolean(true);
+                break;
+            }
+            ++tnBegin;
+        }
+    }
+    return true;
+}
+
 static bool
 DebuggerScript_construct(JSContext *cx, unsigned argc, Value *vp)
 {
@@ -3546,6 +3579,7 @@ static const JSFunctionSpec DebuggerScript_methods[] = {
     JS_FN("getBreakpoints", DebuggerScript_getBreakpoints, 1, 0),
     JS_FN("clearBreakpoint", DebuggerScript_clearBreakpoint, 1, 0),
     JS_FN("clearAllBreakpoints", DebuggerScript_clearAllBreakpoints, 0, 0),
+    JS_FN("isInCatchScope", DebuggerScript_isInCatchScope, 1, 0),
     JS_FS_END
 };