Handle "p S::method()::static_var" in the C++ parser

This commit makes "print S::method()::static_var" actually find the
debug symbol for static_var.  Currently, you get:

  (gdb) print S::method()::static_var
  A syntax error in expression, near `'.

Quoting the whole string would seemingly work before the previous
patch that made GDB stop assuming int for no-debug-info variables:

  (gdb) p 'S::method()::static_var'
  $1 = 1

... except that's incorrect output, because:

  (gdb) ptype 'S::method()::static_var'
  type = <data variable, no debug info>

The way to make it work correctly currently is by quoting the
function/method part, like this:

  (gdb) print 'S::method()'::static_var
  $1 = {i1 = 1, i2 = 2, i3 = 3}
  (gdb) ptype 'S::method()'::static_var
  type = struct aggregate {
      int i1;
      int i2;
      int i3;
  }

At least after the "stop assuming int" patch, this is what we
now get:

  (gdb) p 'S::method()::static_var'
  'S::method()::static_var' has unknown type; cast it to its declared type
  (gdb) p (struct aggregate) 'S::method()::static_var'
  $1 = {i1 = 1, i2 = 2, i3 = 3}

However, IMO, users shouldn't really have to care about any of this.
GDB should Just Work, without quoting, IMO.

So here's a patch that implements support for that in the C++ parser.
With this patch, you now get:

  (gdb) p S::method()::S_M_s_var_aggregate
  $1 = {i1 = 1, i2 = 2, i3 = 3}
  (gdb) ptype S::method()::S_M_s_var_aggregate
  type = struct aggregate {
      int i1;
      int i2;
      int i3;
  }

gdb/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	(%type <voidval>): Add function_method.
	* c-exp.y (exp): New production for calls with no arguments.
	(function_method, function_method_void_or_typelist): New
	productions.
	(exp): New production for "method()::static_var".
	* eval.c (evaluate_subexp_standard): Handle OP_FUNC_STATIC_VAR.
	* expprint.c (print_subexp_standard, dump_subexp_body_standard):
	Handle OP_FUNC_STATIC_VAR.
	* parse.c (operator_length_standard):
	Handle OP_FUNC_STATIC_VAR.
	* std-operator.def (OP_FUNC_STATIC_VAR): New.

gdb/testsuite/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* gdb.base/local-static.c: New.
	* gdb.base/local-static.cc: New.
	* gdb.base/local-static.exp:  New.

1 files changed, 6 insertions, 0 deletions

diff --git a/gdb/parse.c b/gdb/parse.c
index 3db97351dcd..e1fa229230c 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -901,6 +901,12 @@ operator_length_standard (const struct expression *expr, int endpos,
       oplen = 4;
       break;
 
+    case OP_FUNC_STATIC_VAR:
+      oplen = longest_to_int (expr->elts[endpos - 2].longconst);
+      oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
+      args = 1;
+      break;
+
     case OP_TYPE:
     case OP_BOOL:
     case OP_LAST: