[gcc r11-8490] libcpp: Fix up -fdirectives-only handling of // comments on last line not terminated with newline [P

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:3a2fa2e819d4714cecf5048eda2b7e52ba9e3cdd

commit r11-8490-g3a2fa2e819d4714cecf5048eda2b7e52ba9e3cdd
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu May 20 09:09:07 2021 +0200

    libcpp: Fix up -fdirectives-only handling of // comments on last line not terminated with newline [PR100646]
    
    As can be seen on the testcases, before the -fdirectives-only preprocessing
    rewrite the preprocessor would assume // comments are terminated by the
    end of file even when newline wasn't there, but now we error out.
    The following patch restores the previous behavior.
    
    2021-05-20  Jakub Jelinek  <jakub@redhat.com>
    
            PR preprocessor/100646
            * lex.c (cpp_directive_only_process): Treat end of file as termination
            for !is_block comments.
    
            * gcc.dg/cpp/pr100646-1.c: New test.
            * gcc.dg/cpp/pr100646-2.c: New test.
    
    (cherry picked from commit d15a2d261b24adcbfe5e663b15dde3df5d2b3486)

Diff:
---
 gcc/testsuite/gcc.dg/cpp/pr100646-1.c | 5 +++++
 gcc/testsuite/gcc.dg/cpp/pr100646-2.c | 6 ++++++
 libcpp/lex.c                          | 5 +++--
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/cpp/pr100646-1.c b/gcc/testsuite/gcc.dg/cpp/pr100646-1.c
new file mode 100644
index 00000000000..8f2caf40c3f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/pr100646-1.c
@@ -0,0 +1,5 @@
+/* PR preprocessor/100646 */
+/* { dg-do compile } */
+/* { dg-options "-fdirectives-only -save-temps -std=c17" } */
+int main () { return 0; }
+// Not newline terminated
\ No newline at end of file
diff --git a/gcc/testsuite/gcc.dg/cpp/pr100646-2.c b/gcc/testsuite/gcc.dg/cpp/pr100646-2.c
new file mode 100644
index 00000000000..a1deba10634
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/pr100646-2.c
@@ -0,0 +1,6 @@
+/* PR preprocessor/100646 */
+/* { dg-do compile } */
+/* { dg-options "-fdirectives-only -save-temps -std=c17" } */
+int main () { return 0; }
+/* { dg-warning "backslash-newline at end of file" "" { target *-*-* } .+1 } */
+// Not newline terminated\
\ No newline at end of file
diff --git a/libcpp/lex.c b/libcpp/lex.c
index 6c0ca8d2e2d..3791f388207 100644
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -4469,8 +4469,9 @@ cpp_directive_only_process (cpp_reader *pfile,
 			break;
 		      }
 		  }
-		cpp_error_with_line (pfile, CPP_DL_ERROR, sloc, 0,
-				     "unterminated comment");
+		if (pos < limit || is_block)
+		  cpp_error_with_line (pfile, CPP_DL_ERROR, sloc, 0,
+				       "unterminated comment");
 	      done_comment:
 		lwm = pos;
 		break;