Don't allow empty expression in CXFA_FMParse::ParseParenExpression.

BUG=pdfium:404
R=jun_fang@foxitsoftware.com, tsepez@chromium.org

Review URL: https://codereview.chromium.org/1742903002 .

3 files changed, 21 insertions, 17 deletions

diff --git a/xfa/src/fxfa/src/fm2js/xfa_error.cpp b/xfa/src/fxfa/src/fm2js/xfa_error.cpp
index fdeee363bb..03423b0673 100644
--- a/xfa/src/fxfa/src/fm2js/xfa_error.cpp
+++ b/xfa/src/fxfa/src/fm2js/xfa_error.cpp
@@ -11,6 +11,7 @@ static const FX_WCHAR* const gs_lpStrErrorMsgInfo[] = {
     L"invalidate char '%c'",          L"expected identifier instead of '%s'",
     L"expected '%s' instead of '%s'", L"expected 'endif' instead of '%s'",
     L"unexpected expression '%s'",    L"expected operator '%s' instead of '%s'",
+    L"expected non-empty expression",
 };
 
 const FX_WCHAR* XFA_FM_ErrorMsg(XFA_FM_ERRMSG msg) {
diff --git a/xfa/src/fxfa/src/fm2js/xfa_error.h b/xfa/src/fxfa/src/fm2js/xfa_error.h
index 474b28b7c9..8907ad872f 100644
--- a/xfa/src/fxfa/src/fm2js/xfa_error.h
+++ b/xfa/src/fxfa/src/fm2js/xfa_error.h
@@ -19,6 +19,7 @@ enum XFA_FM_ERRMSG {
   FMERR_EXPECTED_IFEND,
   FMERR_UNEXPECTED_EXPRESSION,
   FMERR_EXPTECTED_OPERATOR,
+  FMERR_EXPECTED_NON_EMPTY_EXPRESSION,
   FMERR_MAXIMUM
 };
 
diff --git a/xfa/src/fxfa/src/fm2js/xfa_fmparse.cpp b/xfa/src/fxfa/src/fm2js/xfa_fmparse.cpp
index 6841cdaca5..bd2c206f03 100644
--- a/xfa/src/fxfa/src/fm2js/xfa_fmparse.cpp
+++ b/xfa/src/fxfa/src/fm2js/xfa_fmparse.cpp
@@ -782,26 +782,28 @@ CXFA_FMSimpleExpression* CXFA_FMParse::ParseIndexExpression() {
 }
 
 CXFA_FMSimpleExpression* CXFA_FMParse::ParseParenExpression() {
-  FX_DWORD line = m_pToken->m_uLinenum;
   Check(TOKlparen);
-  std::unique_ptr<CXFA_FMSimpleExpression> pExp1;
-  if (m_pToken->m_type != TOKrparen) {
-    pExp1.reset(ParseLogicalOrExpression());
-    while (m_pToken->m_type == TOKassign) {
-      NextToken();
-      std::unique_ptr<CXFA_FMSimpleExpression> pExp2(
-          ParseLogicalOrExpression());
-      if (m_pErrorInfo->message.IsEmpty()) {
-        pExp1.reset(new CXFA_FMAssignExpression(
-            line, TOKassign, pExp1.release(), pExp2.release()));
-      } else {
-        pExp1.reset();
-      }
-    }
-    Check(TOKrparen);
-  } else {
+
+  if (m_pToken->m_type == TOKrparen) {
+    Error(m_pToken->m_uLinenum, FMERR_EXPECTED_NON_EMPTY_EXPRESSION);
     NextToken();
+    return nullptr;
   }
+
+  FX_DWORD line = m_pToken->m_uLinenum;
+  std::unique_ptr<CXFA_FMSimpleExpression> pExp1(ParseLogicalOrExpression());
+
+  while (m_pToken->m_type == TOKassign) {
+    NextToken();
+    std::unique_ptr<CXFA_FMSimpleExpression> pExp2(ParseLogicalOrExpression());
+    if (m_pErrorInfo->message.IsEmpty()) {
+      pExp1.reset(new CXFA_FMAssignExpression(line, TOKassign, pExp1.release(),
+                                              pExp2.release()));
+    } else {
+      pExp1.reset();
+    }
+  }
+  Check(TOKrparen);
   return pExp1.release();
 }