gdb/gdb-rhbz1964167-fortran-array-strides-in-expressions.patch

From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
From: Kevin Buettner <kevinb@redhat.com>
Date: Mon, 24 May 2021 22:30:32 -0700
Subject: gdb-rhbz1964167-fortran-array-strides-in-expressions.patch

;; [fortran] Backport Andrew Burgess's commit which adds support
;; for array strides in expressions.

gdb/fortran: add support for parsing array strides in expressions

With this commit GDB now understands the syntax of Fortran array
strides, a user can type an expression including an array stride, but
they will only get an error informing them that array strides are not
supported.

This alone is an improvement on what we had before in GDB, better to
give the user a helpful message that a particular feature is not
supported than to just claim a syntax error.

Before:

  (gdb) p array (1:10:2, 2:10:2)
  A syntax error in expression, near `:2, 2:10:2)'.

Now:

  (gdb) p array (1:10:2, 2:10:2)
  Fortran array strides are not currently supported

Later commits will allow GDB to handle array strides correctly.

gdb/ChangeLog:

	* expprint.c (dump_subexp_body_standard): Print RANGE_HAS_STRIDE.
	* expression.h (enum range_type): Add RANGE_HAS_STRIDE.
	* f-exp.y (arglist): Allow for a series of subranges.
	(subrange): Add cases for subranges with strides.
	* f-lang.c (value_f90_subarray): Catch use of array strides and
	throw an error.
	* parse.c (operator_length_standard): Handle RANGE_HAS_STRIDE.

gdb/testsuite/ChangeLog:

	* gdb.fortran/array-slices.exp: Add a new test.

diff --git a/gdb/expprint.c b/gdb/expprint.c
--- a/gdb/expprint.c
+++ b/gdb/expprint.c
@@ -1118,12 +1118,16 @@ dump_subexp_body_standard (struct expression *exp,
 	fputs_filtered ("..", stream);
 	if (!(range_flag & RANGE_HIGH_BOUND_DEFAULT))
 	  fputs_filtered ("EXP", stream);
+	if (range_flag & RANGE_HAS_STRIDE)
+	  fputs_filtered (":EXP", stream);
 	fputs_filtered ("'", stream);
 
 	if (!(range_flag & RANGE_LOW_BOUND_DEFAULT))
 	  elt = dump_subexp (exp, stream, elt);
 	if (!(range_flag & RANGE_HIGH_BOUND_DEFAULT))
 	  elt = dump_subexp (exp, stream, elt);
+	if (range_flag & RANGE_HAS_STRIDE)
+	  elt = dump_subexp (exp, stream, elt);
       }
       break;
 
diff --git a/gdb/expression.h b/gdb/expression.h
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -199,6 +199,9 @@ enum range_flag : unsigned
 
   /* The high bound of this range is exclusive.  */
   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
+
+  /* The range has a stride.  */
+  RANGE_HAS_STRIDE = 1 << 3,
 };
 
 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
diff --git a/gdb/f-exp.y b/gdb/f-exp.y
--- a/gdb/f-exp.y
+++ b/gdb/f-exp.y
@@ -284,6 +284,10 @@ arglist	:	arglist ',' exp   %prec ABOVE_COMMA
 			{ pstate->arglist_len++; }
 	;
 
+arglist	:	arglist ',' subrange   %prec ABOVE_COMMA
+			{ pstate->arglist_len++; }
+	;
+
 /* There are four sorts of subrange types in F90.  */
 
 subrange:	exp ':' exp	%prec ABOVE_COMMA
@@ -314,6 +318,38 @@ subrange:	':'	%prec ABOVE_COMMA
 			  write_exp_elt_opcode (pstate, OP_RANGE); }
 	;
 
+/* And each of the four subrange types can also have a stride.  */
+subrange:	exp ':' exp ':' exp	%prec ABOVE_COMMA
+			{ write_exp_elt_opcode (pstate, OP_RANGE);
+			  write_exp_elt_longcst (pstate, RANGE_HAS_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,
+						 (RANGE_HIGH_BOUND_DEFAULT
+						  | RANGE_HAS_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,
+						 (RANGE_LOW_BOUND_DEFAULT
+						  | RANGE_HAS_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,
+						 (RANGE_LOW_BOUND_DEFAULT
+						  | RANGE_HIGH_BOUND_DEFAULT
+						  | RANGE_HAS_STRIDE));
+			  write_exp_elt_opcode (pstate, OP_RANGE); }
+	;
+
 complexnum:     exp ',' exp 
                 	{ }                          
         ;
diff --git a/gdb/f-lang.c b/gdb/f-lang.c
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -124,7 +124,7 @@ value_f90_subarray (struct value *array,
 		    struct expression *exp, int *pos, enum noside noside)
 {
   int pc = (*pos) + 1;
-  LONGEST low_bound, high_bound;
+  LONGEST low_bound, high_bound, stride;
   struct type *range = check_typedef (value_type (array)->index_type ());
   enum range_flag range_flag
     = (enum range_flag) longest_to_int (exp->elts[pc].longconst);
@@ -141,6 +141,14 @@ value_f90_subarray (struct value *array,
   else
     high_bound = value_as_long (evaluate_subexp (nullptr, exp, pos, noside));
 
+  if (range_flag & RANGE_HAS_STRIDE)
+    stride = value_as_long (evaluate_subexp (nullptr, exp, pos, noside));
+  else
+    stride = 1;
+
+  if (stride != 1)
+    error (_("Fortran array strides are not currently supported"));
+
   return value_slice (array, low_bound, high_bound - low_bound + 1);
 }
 
diff --git a/gdb/parse.c b/gdb/parse.c
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -924,6 +924,8 @@ operator_length_standard (const struct expression *expr, int endpos,
       /* Assume the range has 2 arguments (low bound and high bound), then
 	 reduce the argument count if any bounds are set to default.  */
       args = 2;
+      if (range_flag & RANGE_HAS_STRIDE)
+	++args;
       if (range_flag & RANGE_LOW_BOUND_DEFAULT)
 	--args;
       if (range_flag & RANGE_HIGH_BOUND_DEFAULT)
diff --git a/gdb/testsuite/gdb.fortran/array-slices.exp b/gdb/testsuite/gdb.fortran/array-slices.exp
--- a/gdb/testsuite/gdb.fortran/array-slices.exp
+++ b/gdb/testsuite/gdb.fortran/array-slices.exp
@@ -66,3 +66,19 @@ foreach result $array_contents msg $message_strings {
 }
 
 gdb_continue_to_breakpoint "continue to Final Breakpoint"
+
+# Next test that asking for an array with stride at the CLI gives an
+# error.
+clean_restart ${testfile}
+
+if ![fortran_runto_main] then {
+    perror "couldn't run to main"
+    continue
+}
+
+gdb_breakpoint "show"
+gdb_continue_to_breakpoint "show"
+gdb_test "up" ".*"
+gdb_test "p array (1:10:2, 1:10:2)" \
+    "Fortran array strides are not currently supported" \
+    "using array stride gives an error"