[Crash-utility] display function parameters for call stack

[Dave Anderson]

----- Original Message -----

> 
> I find print_frame_args in gdb/stack.c seems to be the function to print out
> the argument's name. Its working mechanism is exacting out all symbols
> in the specified function with ALL_BLOCK_SYMBOLS. Then discard those symbol
> not as argument by SYMBOL_IS_ARGUMENT.  At last it would get the argument 
> name by SYMBOL_PRINT_NAME.

I think the problem you'll have there is the frame_info structure that
gets passed in to print_frame_args().  But maybe you can pull out a
subset of that function to just access the argument names from the
text symbol?

> 
> So how could I reach this print_frame_args by crash, need modify gdb side
> to create such helper function?
> I am not familiar with the gdb modification...
> Is there any example to show me how to do this change?
> It is better that the example itself contains how to connect the
> change with crash. :)

For examples, check out any of the current users of gdb_interface().
They all set up a gnu_request structure with a command and any other
information required, and pass it into the gdb module.

To test your code, you can borrow the GNU_DEBUG_COMMAND command.

For example, you could create a function like this, which passes
the text symbol's name into the gdb module:
 
  your_function(char *text_symbol)
  {
          struct gnu_request request, *req = &request;

          req->command = GNU_DEBUG_COMMAND;
          req->flags |= GNU_RETURN_ON_ERROR;
          req->name = text_symbol;
          /*
           * fill in any other fields in the gnu_request struct 
           */
          gdb_interface(req);
  
          if (req->flags & GNU_COMMAND_FAILED) {
                  goto error_out;
          }
  
          ...
  }

The gnu_request structure has several other general-purpose members
that you can use if more than the symbol name string is required.
  
Then, the gdb_interface() call above will end up here in
gdb-7.3.1/gdb/symtab.c:
  
  void
  gdb_command_funnel(struct gnu_request *req)
  {
          struct symbol *sym;
  
          if (req->command != GNU_VERSION) {
                  replace_ui_file_FILE(gdb_stdout, req->fp);
                  replace_ui_file_FILE(gdb_stderr, req->fp);
                  do_cleanups((struct cleanup *)0);
          }
  
          switch (req->command)
          {
          ...[ cut ] ...
  
          case GNU_DEBUG_COMMAND:
                  gdb_debug_command(req);
                  break;
  
         ... [ cut ] ...
  }
  
And you can do whatever you want in gdb_debug_command(), which is 
also located in gdb-7.3.1/gdb/symtab.c:
  
  static void
  gdb_debug_command(struct gnu_request *req)
  {
  
  }
  
If you can get something working, we can add a new gdb
GNU_XXXX command that does what you want.
  
Dave