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Re: [PATCH 3/5] introduce the binding oracle


On 05/16/14 09:26, Tom Tromey wrote:
gdb wants to supply any declarations that may be referred to by the
user's code.  Hooking into symbol lookup was an efficient way to
accomplish this.

This patch introducing a "binding oracle" that is consulted whenever a
symbol binding is looked up for the first time.  The oracle is just a
global function pointer.  If it is NULL, no special work is done.  It
is called with the identifier to supply and with an enum argument
indicating the kind of binding being requested.  The oracle can then
call back into the C front end (via the new functions c_pushtag and
c_bind) to supply a binding; or it can silently do nothing if the
request could not be fulfilled.

The code caches Whether the oracle has been called to avoid repeated
useless queries.

There is a little hack in c_print_identifier to avoid calling the
binding oracle here.  This makes debugging gcc in the presence of the
plugin remain relatively sane -- without this, calling debug_tree or
the like can confusingly call into the plugin.

2014-05-16  Phil Muldoon  <pmuldoon@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* c-tree.h (enum c_oracle_request): New.
	(c_binding_oracle_function): New typedef.
	(c_binding_oracle, c_pushtag, c_bind): Declare.
	* c-decl.c (c_binding_oracle): New global.
	(I_SYMBOL_CHECKED): New macro.
	(i_symbol_binding): New function.
	(I_SYMBOL_BINDING, I_SYMBOL_DECL): Redefine.
	(I_TAG_CHECKED): New macro.
	(i_tag_binding): New function.
	(I_TAG_BINDING, I_TAG_DECL): Redefine.
	(I_LABEL_CHECKED): New macro.
	(i_label_binding): New function.
	(I_LABEL_BINDING, I_LABEL_DECL): Redefine.
	(c_print_identifier): Save and restore c_binding_oracle.
	(c_pushtag, c_bind): New functions.
---
  void
  c_print_identifier (FILE *file, tree node, int indent)
  {
+  void (*save) (enum c_oracle_request, tree identifier);
+
+  // This makes debugging much more sane.
+  save = c_binding_oracle;
+  c_binding_oracle = NULL;
+
Just a nit. C-style comment would be appreciated. It might also help to clarify what "much more sane" really means here.

Otherwise, it looks OK to me.

jeff


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