From 320389e849f82403049c76ef06d11bfcef7b82e3 Mon Sep 17 00:00:00 2001
From: peter klausler <pklausler@nvidia.com>
Date: Tue, 21 Jul 2020 17:57:06 -0700
Subject: [PATCH] [flang] Fix source line continuation in potential macro calls
 (bugzilla 46768)

The prescanner looks for implicit continuation lines when
there are unclosed parentheses at the end of a line, so that
source preprocessing macro references with arguments that span
lines are recognized.  The condition that determines this
implicit continuation has been put into a predicate member
function and corrected to apply only when the following line
is source (not a preprocessing directive, comment, &c.).

Fixes bugzilla #46768.

Reviewed By: sscalpone

Differential Revision: https://reviews.llvm.org/D84280
---
 flang/lib/Parser/prescan.cpp           | 16 +++++++++++-----
 flang/lib/Parser/prescan.h             |  1 +
 flang/test/Parser/continuation-in-if.f |  9 +++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 flang/test/Parser/continuation-in-if.f

diff --git a/flang/lib/Parser/prescan.cpp b/flang/lib/Parser/prescan.cpp
index 68e1de1e5e44..c81d6cb50846 100644
--- a/flang/lib/Parser/prescan.cpp
+++ b/flang/lib/Parser/prescan.cpp
@@ -887,10 +887,8 @@ const char *Prescanner::FixedFormContinuationLine(bool mightNeedSpace) {
         return nextLine_ + 6;
       }
     }
-    if (delimiterNesting_ > 0) {
-      if (!IsFixedFormCommentChar(col1)) {
-        return nextLine_;
-      }
+    if (IsImplicitContinuation()) {
+      return nextLine_;
     }
   }
   return nullptr; // not a continuation line
@@ -927,7 +925,7 @@ const char *Prescanner::FreeFormContinuationLine(bool ampersand) {
       return p + 1;
     } else if (*p == '!' || *p == '\n' || *p == '#') {
       return nullptr;
-    } else if (ampersand || delimiterNesting_ > 0) {
+    } else if (ampersand || IsImplicitContinuation()) {
       if (p > nextLine_) {
         --p;
       } else {
@@ -981,6 +979,14 @@ bool Prescanner::FreeFormContinuation() {
   return false;
 }
 
+// Implicit line continuation allows a preprocessor macro call with
+// arguments to span multiple lines.
+bool Prescanner::IsImplicitContinuation() const {
+  return !inPreprocessorDirective_ && !inCharLiteral_ &&
+      delimiterNesting_ > 0 && nextLine_ < limit_ &&
+      ClassifyLine(nextLine_).kind == LineClassification::Kind::Source;
+}
+
 bool Prescanner::Continuation(bool mightNeedFixedFormSpace) {
   if (*at_ == '\n' || *at_ == '&') {
     if (inFixedForm_) {
diff --git a/flang/lib/Parser/prescan.h b/flang/lib/Parser/prescan.h
index 393016fde369..6e492a73597b 100644
--- a/flang/lib/Parser/prescan.h
+++ b/flang/lib/Parser/prescan.h
@@ -166,6 +166,7 @@ private:
   const char *IsPreprocessorDirectiveLine(const char *) const;
   const char *FixedFormContinuationLine(bool mightNeedSpace);
   const char *FreeFormContinuationLine(bool ampersand);
+  bool IsImplicitContinuation() const;
   bool FixedFormContinuation(bool mightNeedSpace);
   bool FreeFormContinuation();
   bool Continuation(bool mightNeedFixedFormSpace);
diff --git a/flang/test/Parser/continuation-in-if.f b/flang/test/Parser/continuation-in-if.f
new file mode 100644
index 000000000000..928170eb6cd5
--- /dev/null
+++ b/flang/test/Parser/continuation-in-if.f
@@ -0,0 +1,9 @@
+! RUN: %f18 -funparse %s 2>&1 | FileCheck %s
+! CHECK: CALL foo("N","N")
+#ifdef transpose
+      call foo('T',
+#else
+      call foo('N',
+#endif
+     $     'N')
+      end