RE: [ping] [PATCH v2 0/6] fortran: multi-dimensional subarrays with strides
https://sourceware.org/ml/gdb-patches/2016-07/msg00009.html

From 338e4c860ad205896b4a95c79f54470c79eeb348 Mon Sep 17 00:00:00 2001
From: Christoph Weinmann <christoph.t.weinmann@intel.com>
Date: Wed, 1 Jun 2016 15:11:24 +0200
Subject: [PATCH 4/6] fortran: enable parsing of stride parameter for subranges

Allow the user to provide a stride parameter for Fortran
subarrays.  The stride parameter can be any integer except
'0'.  The default stride value is '1'.

2013-11-27  Christoph Weinmann  <christoph.t.weinmann@intel.com>

	* eval.c (value_f90_subarray): Add expression evaluation
	for a stride parameter in a Fortran range expression.
	* expression.h (range_type): Add field to enum to show when
	a stride value was provided by the user.
	* f-exp.y: Add yacc rules for writing info on the elt stack
	when the user provided a stride argument.
	* parse.c (operator_length_standard): Check if a stride
	value was provided, and increment argument counter
	accordingly.


Signed-off-by: Christoph Weinmann <christoph.t.weinmann@intel.com>
---
 gdb/eval.c       | 11 ++++++++++-
 gdb/expression.h |  7 +++++--
 gdb/f-exp.y      | 31 ++++++++++++++++++++++++++++++-
 gdb/parse.c      |  3 +++
 gdb/valops.c     |  4 ++--
 5 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/gdb/eval.c b/gdb/eval.c
index 44e8600..b5aaf1c 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -419,7 +419,7 @@ value_f90_subarray (struct value *array, struct expression *exp,
   typedef struct subscript_range
   {
     enum range_type f90_range_type;
-    LONGEST low, high;
+    LONGEST low, high, stride;
   } subscript_range;
 
   typedef enum subscript_kind
@@ -490,6 +490,15 @@ value_f90_subarray (struct value *array, struct expression *exp,
 	      == SUBARRAY_HIGH_BOUND)
 	    range->high = value_as_long (evaluate_subexp (NULL_TYPE, exp,
 							  pos, noside));
+
+	  /* Assign the user's stride value if provided.  */
+	  if ((range->f90_range_type & SUBARRAY_STRIDE) == SUBARRAY_STRIDE)
+	    range->stride = value_as_long (evaluate_subexp (NULL_TYPE, exp,
+							     pos, noside));
+
+	  /* Assign the default stride value '1'.  */
+	  else
+	    range->stride = 1;
 	}
       /* User input is an index.  E.g.: "p arry(5)".  */
       else
diff --git a/gdb/expression.h b/gdb/expression.h
index 5a6b720..34ca54b 100644
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -153,13 +153,16 @@ extern void dump_raw_expression (struct expression *,
 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 
 /* In an OP_RANGE expression, either bound can be provided by the user, or not.
-   This enumeration type is to identify this.  */
+   In addition to this, the user can also specify a stride value to indicated
+   only certain elements of the array.  This enumeration type is to identify
+   this.  */
 
 enum range_type
   {
     SUBARRAY_NONE_BOUND = 0x0,		/* "( : )"  */
     SUBARRAY_LOW_BOUND = 0x1,		/* "(low:)"  */
-    SUBARRAY_HIGH_BOUND = 0x2		/* "(:high)"  */
+    SUBARRAY_HIGH_BOUND = 0x2,		/* "(:high)"  */
+    SUBARRAY_STRIDE = 0x4		/* "(::stride)"  */
   };
 
 #endif /* !defined (EXPRESSION_H) */
diff --git a/gdb/f-exp.y b/gdb/f-exp.y
index e2c54b6..71f1823 100644
--- a/gdb/f-exp.y
+++ b/gdb/f-exp.y
@@ -280,7 +280,36 @@ subrange:	':' exp	%prec ABOVE_COMMA
 
 subrange:	':'	%prec ABOVE_COMMA
 			{ write_exp_elt_opcode (pstate, OP_RANGE);
-			  write_exp_elt_longcst (pstate, 0);
+			  write_exp_elt_longcst (pstate, SUBARRAY_NONE_BOUND);
+			  write_exp_elt_opcode (pstate, OP_RANGE); }
+	;
+
+/* Each subrange type can have a stride argument.  */
+subrange:	exp ':' exp ':' exp %prec ABOVE_COMMA
+			{ write_exp_elt_opcode (pstate, OP_RANGE);
+			  write_exp_elt_longcst (pstate, SUBARRAY_LOW_BOUND
+						 | SUBARRAY_HIGH_BOUND
+						 | SUBARRAY_STRIDE);
+			  write_exp_elt_opcode (pstate, OP_RANGE); }
+	;
+
+subrange:	exp ':' ':' exp %prec ABOVE_COMMA
+			{ write_exp_elt_opcode (pstate, OP_RANGE);
+			  write_exp_elt_longcst (pstate, SUBARRAY_LOW_BOUND
+						 | SUBARRAY_STRIDE);
+			  write_exp_elt_opcode (pstate, OP_RANGE); }
+	;
+
+subrange:	':' exp ':' exp %prec ABOVE_COMMA
+			{ write_exp_elt_opcode (pstate, OP_RANGE);
+			  write_exp_elt_longcst (pstate, SUBARRAY_HIGH_BOUND
+						 | SUBARRAY_STRIDE);
+			  write_exp_elt_opcode (pstate, OP_RANGE); }
+	;
+
+subrange:	':' ':' exp %prec ABOVE_COMMA
+			{ write_exp_elt_opcode (pstate, OP_RANGE);
+			  write_exp_elt_longcst (pstate, SUBARRAY_STRIDE);
 			  write_exp_elt_opcode (pstate, OP_RANGE); }
 	;
 
diff --git a/gdb/parse.c b/gdb/parse.c
index 6d54a77..992af87 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -1018,6 +1018,9 @@ operator_length_standard (const struct expression *expr, int endpos,
       if ((range_type & SUBARRAY_HIGH_BOUND) == SUBARRAY_HIGH_BOUND)
 	args++;
 
+      if ((range_type & SUBARRAY_STRIDE) == SUBARRAY_STRIDE)
+	args++;
+
       break;
 
     default:
diff --git a/gdb/valops.c b/gdb/valops.c
index 817a4cf..fbc7dcb 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -3834,7 +3834,7 @@ value_slice_1 (struct value *array, int lowbound, int length, int call_count)
   if (call_count == 1)
     {
       range_type = TYPE_INDEX_TYPE (array_type);
-      slice_range_size = elem_count;
+      slice_range_size = ary_low_bound + elem_count - 1;
 
       /* Check if the array bounds are valid.  */
       if (get_discrete_bounds (range_type, &ary_low_bound, &ary_high_bound) < 0)
@@ -3846,7 +3846,7 @@ value_slice_1 (struct value *array, int lowbound, int length, int call_count)
   else
     {
       range_type = TYPE_INDEX_TYPE (TYPE_TARGET_TYPE (array_type));
-      slice_range_size = (ary_low_bound + row_count - 1) * (elem_count);
+      slice_range_size = ary_low_bound + (row_count * elem_count) - 1;
       ary_low_bound = TYPE_LOW_BOUND (range_type);
     }
 
-- 
2.5.5