re PR fortran/71686 (ICE on broken character continuation)

2016-06-29  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR fortran/71686
	* scanner.c (gfc_next_char_literal): Only decrement nextc if it
	is not NULL.

From-SVN: r237860

gcc/fortran/ChangeLog

+2016-06-29  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
+
+	PR fortran/71686
+	* scanner.c (gfc_next_char_literal): Only decrement nextc if it
+	is not NULL.
+
 2016-06-29  Cesar Philippidis  <cesar@codesourcery.com>
 
 	* openmp.c (match_oacc_clause_gang): Rename to ...

gcc/fortran/scanner.c

@@ -1416,7 +1416,8 @@ restart:
 	{
 	  if (in_string)
 	    {
-	      gfc_current_locus.nextc--;
+	      if (gfc_current_locus.nextc)
+	        gfc_current_locus.nextc--;
 	      if (warn_ampersand && in_string == INSTRING_WARN)
 		gfc_warning (OPT_Wampersand, 
 			     "Missing %<&%> in continued character "
@@ -1427,7 +1428,10 @@ restart:
 	  /* Both !$omp and !$ -fopenmp continuation lines have & on the
 	     continuation line only optionally.  */
 	  else if (openmp_flag || openacc_flag || openmp_cond_flag)
-	    gfc_current_locus.nextc--;
+	    {
+	      if (gfc_current_locus.nextc)
+		  gfc_current_locus.nextc--;
+	    }
 	  else
 	    {
 	      c = ' ';