[PATCH] Handle OP_THIS in tracepoints

[Stan Shebs <stan at codesourcery dot com>]

This one comes up pretty quickly when doing tracepoints in C++; members 
in expressions use OP_THIS, which amounts to shorthand for a reference 
to the implicit argument "this".  Handling is uncomplicated, mimics 
expression evaluation.

Stan

2009-12-23  Stan Shebs  <stan@codesourcery.com>

   * ax-gdb.c (gen_expr): Handle OP_THIS.

Index: ax-gdb.c
===================================================================
RCS file: /cvs/src/src/gdb/ax-gdb.c,v
retrieving revision 1.54
diff -p -r1.54 ax-gdb.c
*** ax-gdb.c    24 Dec 2009 00:40:49 -0000    1.54
--- ax-gdb.c    24 Dec 2009 01:21:21 -0000
***************
*** 35,40 ****
--- 35,41 ----
 #include "regcache.h"
 #include "user-regs.h"
 #include "language.h"
+ #include "dictionary.h"

 /* To make sense of this file, you should read doc/agentexpr.texi.
    Then look at the types and enums in ax-gdb.h.  For the code itself,
*************** gen_expr (struct expression *exp, union
*** 1759,1764 ****
--- 1760,1797 ----
       }
       break;

+     case OP_THIS:
+       {
+     char *name;
+     struct frame_info *frame;
+     struct symbol *func, *sym;
+     struct block *b;
+
+     name = current_language->la_name_of_this;
+     if (!name)
+       error (_("no `this' in current language"));
+
+     frame = get_selected_frame (_("no frame selected"));
+
+     func = get_frame_function (frame);
+     if (!func)
+       error (_("no `%s' in nameless context"), name);
+
+     b = SYMBOL_BLOCK_VALUE (func);
+     if (dict_empty (BLOCK_DICT (b)))
+       error (_("no args, no `%s' in block"), name);
+
+     /* Calling lookup_block_symbol is necessary to get the LOC_REGISTER
+        symbol instead of the LOC_ARG one (if both exist).  */
+     sym = lookup_block_symbol (b, name, NULL, VAR_DOMAIN);
+     if (!sym)
+       error (_("no `%s' found"), name);
+
+     gen_var_ref (exp->gdbarch, ax, value, sym);
+     (*pc) += 2;
+       }
+       break;
+
     case OP_TYPE:
       error (_("Attempt to use a type name as an expression."));