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, 21 insertions, 0 deletions

diff --git a/gdb/std-operator.def b/gdb/std-operator.def
index 3eed2cc..56a9af9 100644
--- a/gdb/std-operator.def
+++ b/gdb/std-operator.def
@@ -280,6 +280,27 @@ OP (OP_OBJC_SELECTOR)
    a string, which, of course, is variable length.  */
 OP (OP_SCOPE)
 
+/* OP_FUNC_STATIC_VAR refers to a function local static variable.  The
+   function is taken from the following subexpression.  The length of
+   the variable name as a string follows the opcode, followed by
+   BYTES_TO_EXP_ELEM(length) elements containing the data of the
+   string, followed by the length again and the opcode again.
+
+   Note this is used by C++, but not C.  The C parser handles local
+   static variables in the parser directly.  Also, this is only used
+   in C++ if the function/method name is not quoted, like e.g.:
+
+     p S:method()::var
+     p S:method() const::var
+
+   If the function/method is quoted like instead:
+
+     p 'S:method() const'::var
+
+   then the C-specific handling directly in the parser takes over (see
+   "block/variable productions).  */
+OP (OP_FUNC_STATIC_VAR)
+
 /* OP_TYPE is for parsing types, and used with the "ptype" command
    so we can look up types that are qualified by scope, either with
    the GDB "::" operator, or the Modula-2 '.' operator.  */