Re: environment for 'shell' command

[Andrew Cagney <ac131313 at ges dot redhat dot com>]

> Hi,
>
> I would like the ability to pass the file name and line number of the
> source corresponding to the selected stack frame to a program started
> via the 'shell' command.  I could not find any way to do this in gdb. 
> If there is a way to do this, please let me know (and disregard the rest
> of this message.)  I decided to add this functionality but I am
> unfimiliar with the internal workings of gdb.  The following is a
> description of what I did to implement this.  I'd really appreciate any
> suggestions on better ways to implement this, error conditions I'm not
> handling, etc.
Off hand I can think of two ways to handle this:

-- extend what you've proposed by including commands to explicitly 
manipulate the exported environment, vis:
(gdb) command-to-set-shell-env VARIABLE VALUE
(gdb) shell printenv VARIABLE
VARIABLE=VALUE
(gdb)
where VALUE is something that GDB could evaluate.
   As I suspect you discovered, there currently isn't a mechanism for 
refering to the current SAL from GDB's command line.
   I think it is better to have explicit commands to manipulate the 
exported environment as that will help make things more transparent.  A 
few defaults wouldn't hurt of course.

-- extend ``shell'' or add a new command that lets expressions that GDB 
evaluates be passed down to the shell.  That way, something like:
(gdb) eval shell $frame.file $frame.line
would pass down the values you need.  (No $frame.file and $frame.line do 
not exist :-).  Hmm, it appears that ``eval'' isn't taken.

Anyone?

(It's time to reach a decision on $frame, $gdbframe $gdb.frame and get 
that committed :-)

Andrew


> The simplest way I could come up with to do this is to put the values in
> environmental variables immediately before executing the command. 
> Specifically, setting gdb_stack_dir, gdb_stack_file, and gdb_stack_line
> to the values from a struct symtab_and_line.  I use this for defining
> things like a 'view' command that highlights the current location in the
> source in a text editor:



>  define view
>    shell if [ x$gdb_stack_file != x ]; then \ 
>             nc -line $gdb_stack_line $gdb_stack_dir$gdb_stack_file; \
>          fi
>  end
>
> I added the following function to stack.c to get a symtab_and_line
> struct for the selected frame:
>
>  /* Get a symtab_and_line for the selected stack frame. */
>  struct symtab_and_line 
>  find_selected_line (void)
>  {
>    struct symtab_and_line sal;
>    INIT_SAL( &sal );
>    if( selected_frame != NULL )
>      sal = find_pc_line(selected_frame->pc, 
>                         selected_frame->next
>                         && !selected_frame->next->signal_handler_caller 
>                         && !frame_in_dummy (selected_frame->next));
>    return sal;
>  }
>
>
> I added a function 'set_shell_environment' to cli/cli-cmds.c and added
> calls to that function in 'shell_escape'.
>
>  #define SHELL_ENV "gdb_stack_"
>
>  static void
>  set_shell_environment()
>  {
>    char buffer[16];
>    struct symtab_and_line sal = find_selected_line();
>    
>    unsetenv (SHELL_ENV "file");
>    unsetenv (SHELL_ENV "dir");
>    unsetenv (SHELL_ENV "line");
>    
>    if (sal.symtab && sal.symtab->filename && sal.symtab->dirname)
>      {
>        sprintf (buffer, "%d", sal.line);
>        setenv (SHELL_ENV "line", buffer, 1);
>        setenv (SHLLL_ENV "dir", sal.symtab->dirname, 1);
>        setenv (SHELL_ENV "file", sal.symtab->filename, 1);
>      } 
>  }      
> thanks,
>
> -- Jason Kraftcheck