From b547e1a4d163721b2dc3be869a3f06c6203217dc Mon Sep 17 00:00:00 2001
From: David Truby <david.truby@arm.com>
Date: Tue, 21 Apr 2020 19:45:43 +0100
Subject: [PATCH] [flang] Fix handling of files without terminating newlines.

Reviewers: sscalpone

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78578
---
 flang/lib/Parser/source.cpp              | 17 ++++++++++++-----
 flang/test/Semantics/missing_newline.f90 |  4 ++++
 2 files changed, 16 insertions(+), 5 deletions(-)
 create mode 100644 flang/test/Semantics/missing_newline.f90

diff --git a/flang/lib/Parser/source.cpp b/flang/lib/Parser/source.cpp
index 376786e3923e..4f6c21fc2b48 100644
--- a/flang/lib/Parser/source.cpp
+++ b/flang/lib/Parser/source.cpp
@@ -127,12 +127,19 @@ bool SourceFile::ReadStandardInput(llvm::raw_ostream &error) {
 }
 
 void SourceFile::ReadFile() {
-  if (buf_->getBuffer().size() == 0) {
-    Close();
-    buf_ = llvm::WritableMemoryBuffer::getNewUninitMemBuffer(1);
-    buf_->getBuffer()[0] = '\n';
-  }
   buf_end_ = RemoveCarriageReturns(buf_->getBuffer());
+  if (content().size() == 0 || content().back() != '\n') {
+    // Don't bother to copy if we have spare memory
+    if (content().size() >= buf_->getBufferSize()) {
+      auto tmp_buf{llvm::WritableMemoryBuffer::getNewUninitMemBuffer(
+          content().size() + 1)};
+      llvm::copy(content(), tmp_buf->getBufferStart());
+      Close();
+      buf_ = std::move(tmp_buf);
+    }
+    buf_end_++;
+    buf_->getBuffer()[buf_end_ - 1] = '\n';
+  }
   IdentifyPayload();
   RecordLineStarts();
 }
diff --git a/flang/test/Semantics/missing_newline.f90 b/flang/test/Semantics/missing_newline.f90
new file mode 100644
index 000000000000..6dfafba7db86
--- /dev/null
+++ b/flang/test/Semantics/missing_newline.f90
@@ -0,0 +1,4 @@
+! RUN: echo -n "end program" > %t.f90
+! RUN: %f18 -fparse-only %t.f90
+! RUN: echo -ne "\rend program" > %t.f90
+! RUN: %f18 -fparse-only %t.f90