[formcalc] Consider width along with depth of tree

When building the formcalc parser trees we need to limit on width along
with depth. It's possible to generate a tree of a single depth but is
more then 20k nodes wide. This will eventuall cause stack overflow
issues.

This CL re-uses the depth check for the grammar expressions in which
we're extending the width of the tree we count that against our depth
check.

Bug: chromium:813346
Change-Id: I01f6567a75776a75374465eacc1ff546db46cac1
Reviewed-on: https://pdfium-review.googlesource.com/28170
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp b/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
index 5ee27b189e..1eedebfcca 100644
--- a/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
+++ b/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
@@ -238,3 +238,22 @@ TEST(CXFA_FMParserTest, ParseBadElseIfExpression) {
   ASSERT_TRUE(ast == nullptr);
   EXPECT_TRUE(parser->HasError());
 }
+
+TEST(CXFA_FMParserTest, ParseDepthWithWideTree) {
+  const wchar_t input[] = {L"a <> b <> c <> d <> e <> f <> g <> h <> i <> j"};
+
+  {
+    auto parser = pdfium::MakeUnique<CXFA_FMParser>(input);
+    std::unique_ptr<CXFA_FMAST> ast = parser->Parse();
+    ASSERT_TRUE(ast);
+    EXPECT_TRUE(!parser->HasError());
+  }
+
+  {
+    auto parser = pdfium::MakeUnique<CXFA_FMParser>(input);
+    parser->SetMaxParseDepthForTest(5);
+    std::unique_ptr<CXFA_FMAST> ast = parser->Parse();
+    ASSERT_TRUE(ast == nullptr);
+    EXPECT_TRUE(parser->HasError());
+  }
+}