[patch, fortran] [5/6 Regression] Line continuation followed by comment character in string fails to compile

[Jerry DeLisle <jvdelisle at charter dot net>]

The attached patch reverts a change I made for pr65456 which caused this
regression and adds a check for quotes farther down in the function.  This
avoids treating a '!' in a string as a comment and wiping the rest of the line.

I found the added code is needed because an interposing quote was falling
through and being changed into an empty space at around line 1393. (I do not
recall the history of why that space is being done)

The patch also updates test case continuation_13.f90. I found another compiler I
use for comparison interprets the continuation differently and is inserting a
space that is not there.  So the format at line 800 is handled differently now
with gfortran and the line 900 format example is added to test both cases with
and without a space just before the continuation.

I think now gfortran has this right, but I do not rule out that I am missing
some obscure rule.  This begs a question about the space character substituted
near line 1393 in scanner.c, but at the moment I do not think it is related.

I have also added a test for the the original problem reported in this PR to
avoid future repeating of the problem. I will provide a Changelog entry for the
testsuite changes.

Regression tested on x86-64-linux.  OK to trunk?  followed to 5.1?

Regards,

Jerry


2015-05-14  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR fortran/65903
	* io.c (format_lex): Change to NONSTRING when checking for
	possible doubled quote.
	* scanner.c (gfc_next_char_literal): Revert change from 64506,
	add a check for quotes, and return.

Index: gcc/fortran/io.c
===================================================================
--- gcc/fortran/io.c	(revision 223105)
+++ gcc/fortran/io.c	(working copy)
@@ -385,7 +385,7 @@ format_lex (void)
 
 	  if (c == delim)
 	    {
-	      c = next_char (INSTRING_NOWARN);
+	      c = next_char (NONSTRING);
 
 	      if (c == '\0')
 		{
Index: gcc/fortran/scanner.c
===================================================================
--- gcc/fortran/scanner.c	(revision 223105)
+++ gcc/fortran/scanner.c	(working copy)
@@ -1272,21 +1272,11 @@ restart:
 	 are still in a string and we are looking for a possible
 	 doubled quote and we end up here. See PR64506.  */
 
-      if (in_string)
+      if (in_string && c != '\n')
 	{
 	  gfc_current_locus = old_loc;
-
-	  if (c == '!')
-	    {
-	      skip_comment_line ();
-	      goto restart;
-	    }
-
-	  if (c != '\n')
-	    {
-	      c = '&';
-	      goto done;
-	    }
+	  c = '&';
+	  goto done;
 	}
 
       if (c != '!' && c != '\n')
@@ -1392,6 +1382,8 @@ restart:
 			     "Missing %<&%> in continued character "
 			     "constant at %C");
 	    }
+	  else if (!in_string && (c == '\'' || c == '"'))
+	      goto done;
 	  /* Both !$omp and !$ -fopenmp continuation lines have & on the
 	     continuation line only optionally.  */
 	  else if (openmp_flag || openacc_flag || openmp_cond_flag)
Index: gcc/testsuite/gfortran.dg/continuation_13.f90
===================================================================
--- gcc/testsuite/gfortran.dg/continuation_13.f90	(revision 223105)
+++ gcc/testsuite/gfortran.dg/continuation_13.f90	(working copy)
@@ -19,6 +19,8 @@ character(25) :: astring
     )
 800 format('This is actually ok.'& !comment
    ' end'  )
+900 format('This is actually ok.' & !comment
+   ' end'  )
 write(astring,100)
 if (astring.ne."This format is OK.") call abort
 write(astring,200)
@@ -34,6 +36,8 @@ if (astring.ne."This format now works.'") call abo
 write(astring,700)
 if (astring.ne."This format now works.'") call abort
 write(astring,800)
+if (astring.ne."This is actually ok.' end") call abort
+write(astring,900)
 if (astring.ne."This is actually ok. end") call abort
 
 end

! { dg-do run }
! { dg-options "-std=gnu" }
! 
character(20) :: astring

100 format ("& notblank !")
200 format ("&          !")

write(astring,100)
if (astring.ne."& notblank !") call abort
!print *, astring
write(astring,200)
if (astring.ne."&          !") call abort
!print *, astring

end