re PR fortran/28081 (Undue compile-time error for zero-sized substring)

	PR fortran/28081

	* resolve.c (resolve_substring): Don't issue out-of-bounds
	error messages when the range has zero size.

	* gfortran.dg/substr_3.f: New test.
	* gfortran.dg/equiv_2.f90: Update expected error message.

From-SVN: r114972

gcc/fortran/ChangeLog

 2006-06-24  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
 
+	PR fortran/28081
+	* resolve.c (resolve_substring): Don't issue out-of-bounds
+	error messages when the range has zero size.
+
+2006-06-24  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
 	PR fortran/23862
 	* lang-specs.h (f95-cpp-input): Pass -ffree-form to f951 unless
 	-ffixed-form is explicitly specified.

gcc/fortran/resolve.c

@@ -2542,7 +2542,9 @@ resolve_substring (gfc_ref * ref)
 	  return FAILURE;
 	}
 
-      if (compare_bound_int (ref->u.ss.start, 1) == CMP_LT)
+      if (compare_bound_int (ref->u.ss.start, 1) == CMP_LT
+	  && (compare_bound (ref->u.ss.end, ref->u.ss.start) == CMP_EQ
+	      || compare_bound (ref->u.ss.end, ref->u.ss.start) == CMP_GT))
 	{
 	  gfc_error ("Substring start index at %L is less than one",
 		     &ref->u.ss.start->where);
@@ -2570,9 +2572,11 @@ resolve_substring (gfc_ref * ref)
 	}
 
       if (ref->u.ss.length != NULL
-	  && compare_bound (ref->u.ss.end, ref->u.ss.length->length) == CMP_GT)
+	  && compare_bound (ref->u.ss.end, ref->u.ss.length->length) == CMP_GT
+	  && (compare_bound (ref->u.ss.end, ref->u.ss.start) == CMP_EQ
+	      || compare_bound (ref->u.ss.end, ref->u.ss.start) == CMP_GT))
 	{
-	  gfc_error ("Substring end index at %L is out of bounds",
+	  gfc_error ("Substring end index at %L exceeds the string length",
 		     &ref->u.ss.start->where);
 	  return FAILURE;
 	}

gcc/testsuite/ChangeLog

+2006-06-24  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
+
+	PR fortran/28081
+	* gfortran.dg/substr_3.f: New test.
+	* gfortran.dg/equiv_2.f90: Update expected error message.
+
 2006-06-24  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/28118

gcc/testsuite/gfortran.dg/equiv_2.f90

@@ -7,7 +7,7 @@
       subroutine broken_equiv2
       character*4 j
       character*2 k
-      equivalence (j(2:3), k(1:5))    ! { dg-error "out of bounds" }
+      equivalence (j(2:3), k(1:5))    ! { dg-error "exceeds the string length" }
       end subroutine
 
       subroutine broken_equiv3

gcc/testsuite/gfortran.dg/substr_3.f

+! { dg-do run }
+! Check that substrings behave correctly even when zero-sized
+      implicit none
+      character(len=10) :: s, t
+      integer :: i, j
+
+      s = "abcdefghij"
+      t(:10) = s(1:)
+      s(16:15) = "foo"
+      s(0:-1) = "foo"
+      if (s /= t) call abort
+      end