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.

1 files changed, 3 insertions, 0 deletions

diff --git a/gdb/expression.h b/gdb/expression.h
index fd483e5..8de7123 100644
--- 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);