[patch,wip] warn on noncontiguous pointers

[Cesar Philippidis <cesar@codesourcery.com>]

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As of GCC 8, gfortran now errors when a pointer with a contiguous
attribute is set to point to a target without a contiguous attribute. I
think this is overly strict, and should probably be demoted to a
pedantic warning as I've done in the attached patch.

I ran into this issue while I was tuning GCC for lsdalton. Specifically,
CMake generates (not exactly because I reduced it) the following test
case for ScaTeLib to determine if that library can be enabled:

program test
   implicit none
   real,pointer :: fptr1(:)
   real,pointer,contiguous :: fptr3(:,:,:)

   allocate(fptr1(12))
   call random_number(fptr1)

   !Test pointer reshape II

   fptr3(1:2,1:2,1:2) => fptr1(4:)
end program

Note how fptr1 doesn't have a contiguous attribute. Does anyone have
thoughts on this? Maybe the ScaTeLib code needs to be updated.

Thanks,
Cesar

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Disable "Assignment to contiguous pointer from non-contiguous target" error

2018-XX-YY  Cesar Philippidis  <cesar@codesourcery.com>

	gcc/fortran/
	* expr.c (gfc_check_pointer_assign): Demote "Assignment to
	contiguous pointer from non-contiguous target" to a warning.
---

diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
index 3315bb840af..74caa4f2d59 100644
--- a/gcc/fortran/expr.c
+++ b/gcc/fortran/expr.c
@@ -3957,13 +3957,13 @@ gfc_check_pointer_assign (gfc_expr *lvalue, gfc_expr *rvalue)
 	  }
     }
 
-  /* Error for assignments of contiguous pointers to targets which is not
+  /* Warn for assignments of contiguous pointers to targets which is not
      contiguous.  Be lenient in the definition of what counts as
      contiguous.  */
 
   if (lhs_attr.contiguous && !gfc_is_simply_contiguous (rvalue, false, true))
-    gfc_error ("Assignment to contiguous pointer from non-contiguous "
-	       "target at %L", &rvalue->where);
+    gfc_warning (OPT_Wpedantic, "Assignment to contiguous pointer from "
+		 "non-contiguous target at %L", &rvalue->where);
 
   /* Warn if it is the LHS pointer may lives longer than the RHS target.  */
   if (warn_target_lifetime
-- 
2.17.1