gdb: New API for tracking innermost block

This commit is preparation for a later change, at this point there
should be no user visible change.

We currently maintain a global innermost_block which tracks the most
inner block encountered when parsing an expression.

This commit wraps the innermost_block into a new class, and switches all
direct accesses to the variable to use the class API.

gdb/ChangeLog:

	* ada-exp.y (write_var_from_sym): Switch to innermost_block API.
	* ada-lang.c (resolve_subexp): Likewise.
	* breakpoint.c (set_breakpoint_condition) Likewise.
	(watch_command_1) Likewise.
	* c-exp.y (variable): Likewise.
	* d-exp.y (PrimaryExpression): Likewise.
	* f-exp.y (variable): Likewise.
	* go-exp.y (variable): Likewise.
	* m2-exp.y (variable): Likewise.
	* objfiles.c (objfile::~objfile): Likewise.
	* p-exp.y (variable): Likewise.
	* parse.c (innermost_block): Change type.
	* parser-defs.h (class innermost_block_tracker): New.
	(innermost_block): Change to innermost_block_tracker.
	* printcmd.c (display_command): Switch to innermost_block API.
	(do_one_display): Likewise.
	* rust-exp.y (do_one_display): Likewise.
	* symfile.c (clear_symtab_users): Likewise.
	* varobj.c (varobj_create): Switch to innermost_block API, replace
	use of innermost_block with block stored on varobj object.

1 files changed, 45 insertions, 3 deletions

diff --git a/gdb/parser-defs.h b/gdb/parser-defs.h
index c537ed4..01ac0cd 100644
--- a/gdb/parser-defs.h
+++ b/gdb/parser-defs.h
@@ -75,9 +75,51 @@ extern const struct block *expression_context_block;
    then look up the macro definitions active at that point.  */
 extern CORE_ADDR expression_context_pc;
 
-/* The innermost context required by the stack and register variables
-   we've encountered so far.  */
-extern const struct block *innermost_block;
+/* When parsing expressions we track the innermost block that was
+   referenced.  */
+
+class innermost_block_tracker
+{
+public:
+  innermost_block_tracker ()
+    : m_innermost_block (NULL)
+  { /* Nothing.  */ }
+
+  /* Reset the currently stored innermost block.  Usually called before
+     parsing a new expression.  */
+  void reset ()
+  {
+    m_innermost_block = nullptr;
+  }
+
+  /* Update the stored innermost block if the new block B is more inner
+     than the currently stored block, or if no block is stored yet.  */
+  void update (const struct block *b);
+
+  /* Overload of main UPDATE method which extracts the block from BS.  */
+  void update (const struct block_symbol &bs)
+  {
+    update (bs.block);
+  }
+
+  /* Return the stored innermost block.  Can be nullptr if no symbols or
+     registers were found during an expression parse, and so no innermost
+     block was defined.  */
+  const struct block *block () const
+  {
+    return m_innermost_block;
+  }
+
+private:
+  /* The currently stored innermost block found while parsing an
+     expression.  */
+  const struct block *m_innermost_block;
+};
+
+/* The innermost context required by the stack and register variables we've
+   encountered so far.  This should be cleared before parsing an
+   expression, and queried once the parse is complete.  */
+extern innermost_block_tracker innermost_block;
 
 /* Number of arguments seen so far in innermost function call.  */
 extern int arglist_len;