Make some dwarf_expr_context methods pure virtual

This patch changes some dwarf_expr_context to be pure virtual, as
mentioned during the discussion of an earlier patch in this series.

2016-10-21  Tom Tromey  <tom@tromey.com>

	* dwarf2expr.h (class dwarf_expr_context)
	<get_frame_base, get_frame_cfa, get_tls_address, dwarf_call,
	push_dwarf_block_entry_value, get_addr_index, get_object_address>:
	Now pure virtual.
	* dwarf2-frame.c (class dwarf_expr_executor)
	<get_frame_base, get_frame_cfa, get_tls_address, dwarf_call,
	push_dwarf_block_entry_value, get_addr_index, get_object_address>:
	New methods.
	<invalid>: New method.

3 files changed, 63 insertions, 31 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bd49cf4..be72369 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,17 @@
 2016-10-21  Tom Tromey  <tom@tromey.com>
 
+	* dwarf2expr.h (class dwarf_expr_context)
+	<get_frame_base, get_frame_cfa, get_tls_address, dwarf_call,
+	push_dwarf_block_entry_value, get_addr_index, get_object_address>:
+	Now pure virtual.
+	* dwarf2-frame.c (class dwarf_expr_executor)
+	<get_frame_base, get_frame_cfa, get_tls_address, dwarf_call,
+	push_dwarf_block_entry_value, get_addr_index, get_object_address>:
+	New methods.
+	<invalid>: New method.
+
+2016-10-21  Tom Tromey  <tom@tromey.com>
+
 	* minsyms.h (minimal_symbol_reader::record_full): "copy_name" now
 	a bool.
 	(record, record_with_info): Update.
diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index c9962e1..beab304 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -351,6 +351,50 @@ class dwarf_expr_executor : public dwarf_expr_context
   {
     read_memory (addr, buf, len);
   }
+
+  void get_frame_base (const gdb_byte **start, size_t *length) OVERRIDE
+  {
+    invalid ("DW_OP_fbreg");
+  }
+
+  void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
+				   union call_site_parameter_u kind_u,
+				   int deref_size) OVERRIDE
+  {
+    invalid ("DW_OP_GNU_entry_value");
+  }
+
+  CORE_ADDR get_object_address () OVERRIDE
+  {
+    invalid ("DW_OP_push_object_address");
+  }
+
+  CORE_ADDR get_frame_cfa () OVERRIDE
+  {
+    invalid ("DW_OP_call_frame_cfa");
+  }
+
+  CORE_ADDR get_tls_address (CORE_ADDR offset) OVERRIDE
+  {
+    invalid ("DW_OP_form_tls_address");
+  }
+
+  void dwarf_call (cu_offset die_offset) OVERRIDE
+  {
+    invalid ("DW_OP_call*");
+  }
+
+  CORE_ADDR get_addr_index (unsigned int index)
+  {
+    invalid ("DW_OP_GNU_addr_index");
+  }
+
+ private:
+
+  void invalid (const char *op) ATTRIBUTE_NORETURN
+  {
+    error (_("%s is invalid in this context"), op);
+  }
 };
 
 static CORE_ADDR
diff --git a/gdb/dwarf2expr.h b/gdb/dwarf2expr.h
index 63bdc6e..7bf194a 100644
--- a/gdb/dwarf2expr.h
+++ b/gdb/dwarf2expr.h
@@ -156,16 +156,10 @@ struct dwarf_expr_context
   /* Return the location expression for the frame base attribute, in
      START and LENGTH.  The result must be live until the current
      expression evaluation is complete.  */
-  virtual void get_frame_base (const gdb_byte **start, size_t *length)
-  {
-    error (_("%s is invalid in this context"), "DW_OP_fbreg");
-  }
+  virtual void get_frame_base (const gdb_byte **start, size_t *length) = 0;
 
   /* Return the CFA for the frame.  */
-  virtual CORE_ADDR get_frame_cfa ()
-  {
-    error (_("%s is invalid in this context"), "DW_OP_call_frame_cfa");
-  }
+  virtual CORE_ADDR get_frame_cfa () = 0;
 
   /* Return the PC for the frame.  */
   virtual CORE_ADDR get_frame_pc ()
@@ -175,19 +169,13 @@ struct dwarf_expr_context
 
   /* Return the thread-local storage address for
      DW_OP_GNU_push_tls_address or DW_OP_form_tls_address.  */
-  virtual CORE_ADDR get_tls_address (CORE_ADDR offset)
-  {
-    error (_("%s is invalid in this context"), "DW_OP_form_tls_address");
-  }
+  virtual CORE_ADDR get_tls_address (CORE_ADDR offset) = 0;
 
   /* Execute DW_AT_location expression for the DWARF expression
      subroutine in the DIE at DIE_OFFSET in the CU.  Do not touch
      STACK while it being passed to and returned from the called DWARF
      subroutine.  */
-  virtual void dwarf_call (cu_offset die_offset)
-  {
-    error (_("%s is invalid in this context"), "DW_OP_call*");
-  }
+  virtual void dwarf_call (cu_offset die_offset) = 0;
 
   /* Return the base type given by the indicated DIE.  This can throw
      an exception if the DIE is invalid or does not represent a base
@@ -206,26 +194,14 @@ struct dwarf_expr_context
      DW_AT_GNU_call_site_value.  */
   virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
 					   union call_site_parameter_u kind_u,
-					   int deref_size)
-  {
-    internal_error (__FILE__, __LINE__,
-		    _("Support for DW_OP_GNU_entry_value is unimplemented"));
-  }
+					   int deref_size) = 0;
 
   /* Return the address indexed by DW_OP_GNU_addr_index.
      This can throw an exception if the index is out of range.  */
-  virtual CORE_ADDR get_addr_index (unsigned int index)
-  {
-    error (_("%s is invalid in this context"), "DW_OP_GNU_addr_index");
-  }
+  virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
 
   /* Return the `object address' for DW_OP_push_object_address.  */
-  virtual CORE_ADDR get_object_address ()
-  {
-    internal_error (__FILE__, __LINE__,
-		    _("Support for DW_OP_push_object_address "
-		      "is unimplemented"));
-  }
+  virtual CORE_ADDR get_object_address () = 0;
 
 private: