Re: [PATCH] Make only user-specified executable filenames sticky

[Don Breazeal <donb at codesourcery dot com>]

On 5/6/2015 3:26 AM, Gary Benson wrote:
> Hi all,
> 
> In GDB some executable files are supplied by the user (e.g. using a
> "file" command) and some are determined by GDB (e.g. while processing
> an "attach" command).  GDB will not attempt to determine a filename if
> one has been set.  This causes problems if you attach to one process
> and then attach to another: GDB will not attempt to discover the main
> executable on the second attach.  If the two processes have different
> main executable files then the symbols will now be wrong.
> 
> This commit updates GDB to keep track of which executable filenames
> were supplied by the user.  When GDB might attempt to determine an
> executable filename and one is already set, filenames determined by
> GDB may be overridden but user-supplied filenames will not.
> 
> Built and regtested on RHEL6.6 x86_64.
> 
> Is this ok to commit?
> 
> Cheers,
> Gary
> 
> 
> gdb/ChangeLog:
> 
> 	* progspace.h (struct program_space)
> 	<pspace_user_supplied_exec_file_p>: New field.
> 	* exec.h (user_supplied_exec_file_p): New macro.
> 	* exec.c (exec_close): Clear user_supplied_exec_file_p.
> 	(exec_file_locate_attach): Remove get_exec_file check.
> 	(exec_file_command): Set user_supplied_exec_file_p.
> 	* inferior.c (add_inferior_command): Likewise.
> 	* main.c (captured_main): Likewise.
> 	* infcmd.c (attach_command_post_wait): Always try and
> 	locate main executable if !user_supplied_exec_file_p.
> 	* remote.c (remote_add_inferior): Likewise.
> ---
>  gdb/ChangeLog   |   14 ++++++++++++++
>  gdb/exec.c      |    7 ++-----
>  gdb/exec.h      |    2 ++
>  gdb/infcmd.c    |   12 +++++++-----
>  gdb/inferior.c  |    1 +
>  gdb/main.c      |   16 +++++++++++-----
>  gdb/progspace.h |    7 +++++++
>  gdb/remote.c    |    7 ++++---
>  8 files changed, 48 insertions(+), 18 deletions(-)
> 
> diff --git a/gdb/exec.c b/gdb/exec.c
> index 8a4ab6f..278df83 100644
> --- a/gdb/exec.c
> +++ b/gdb/exec.c
> @@ -102,6 +102,7 @@ exec_close (void)
>  
>        xfree (exec_filename);
>        exec_filename = NULL;
> +      user_supplied_exec_file_p = 0;
>      }
>  }
>  
> @@ -142,11 +143,6 @@ exec_file_locate_attach (int pid, int from_tty)
>  {
>    char *exec_file, *full_exec_path = NULL;
>  
> -  /* Do nothing if we already have an executable filename.  */
> -  exec_file = (char *) get_exec_file (0);
> -  if (exec_file != NULL)
> -    return;
> -
>    /* Try to determine a filename from the process itself.  */
>    exec_file = target_pid_to_exec_file (pid);
>    if (exec_file == NULL)
> @@ -376,6 +372,7 @@ exec_file_command (char *args, int from_tty)
>        filename = tilde_expand (*argv);
>        make_cleanup (xfree, filename);
>        exec_file_attach (filename, from_tty);
> +      user_supplied_exec_file_p = 1;
>  
>        do_cleanups (cleanups);
>      }
> diff --git a/gdb/exec.h b/gdb/exec.h
> index c7f3b56..3794aba 100644
> --- a/gdb/exec.h
> +++ b/gdb/exec.h
> @@ -32,6 +32,8 @@ struct objfile;
>  #define exec_bfd current_program_space->ebfd
>  #define exec_bfd_mtime current_program_space->ebfd_mtime
>  #define exec_filename current_program_space->pspace_exec_filename
> +#define user_supplied_exec_file_p \
> +  current_program_space->pspace_user_supplied_exec_file_p
>  
>  /* Builds a section table, given args BFD, SECTABLE_PTR, SECEND_PTR.
>     Returns 0 if OK, 1 on error.  */
> diff --git a/gdb/infcmd.c b/gdb/infcmd.c
> index 7e2484b..491cbb6 100644
> --- a/gdb/infcmd.c
> +++ b/gdb/infcmd.c
> @@ -2467,15 +2467,17 @@ attach_command_post_wait (char *args, int from_tty, int async_exec)
>    inferior = current_inferior ();
>    inferior->control.stop_soon = NO_STOP_QUIETLY;
>  
> -  /* If no exec file is yet known, try to determine it from the
> -     process itself.  */
> -  if (get_exec_file (0) == NULL)
> -    exec_file_locate_attach (ptid_get_pid (inferior_ptid), from_tty);
> -  else
> +  if (user_supplied_exec_file_p)
>      {
>        reopen_exec_file ();
>        reread_symbols ();
>      }
> +  else
> +    {
> +      /* Attempt to open the file that was executed to create this
> +	 inferior.  */
> +      exec_file_locate_attach (ptid_get_pid (inferior_ptid), from_tty);
> +    }
>  
>    /* Take any necessary post-attaching actions for this platform.  */
>    target_post_attach (ptid_get_pid (inferior_ptid));
> diff --git a/gdb/inferior.c b/gdb/inferior.c
> index ba320b5..87b2133 100644
> --- a/gdb/inferior.c
> +++ b/gdb/inferior.c
> @@ -889,6 +889,7 @@ add_inferior_command (char *args, int from_tty)
>  
>  	  exec_file_attach (exec, from_tty);
>  	  symbol_file_add_main (exec, from_tty);
> +	  user_supplied_exec_file_p = 1;
>  	}
>      }
>  
> diff --git a/gdb/main.c b/gdb/main.c
> index 477fd68..9d8a196 100644
> --- a/gdb/main.c
> +++ b/gdb/main.c
> @@ -1051,14 +1051,20 @@ captured_main (void *data)
>           catch_command_errors returns non-zero on success!  */
>        if (catch_command_errors_const (exec_file_attach, execarg,
>  				      !batch_flag))
> -	catch_command_errors_const (symbol_file_add_main, symarg,
> -				    !batch_flag);
> +	{
> +	  user_supplied_exec_file_p = 1;
> +
> +	  catch_command_errors_const (symbol_file_add_main, symarg,
> +				      !batch_flag);
> +	}
>      }
>    else
>      {
> -      if (execarg != NULL)
> -	catch_command_errors_const (exec_file_attach, execarg,
> -				    !batch_flag);
> +      if (execarg != NULL
> +	  && catch_command_errors_const (exec_file_attach, execarg,
> +					 !batch_flag))
> +	user_supplied_exec_file_p = 1;
> +
>        if (symarg != NULL)
>  	catch_command_errors_const (symbol_file_add_main, symarg,
>  				    !batch_flag);
> diff --git a/gdb/progspace.h b/gdb/progspace.h
> index f960093..f8c39b6 100644
> --- a/gdb/progspace.h
> +++ b/gdb/progspace.h
> @@ -154,6 +154,13 @@ struct program_space
>         It needs to be freed by xfree.  It is not NULL iff EBFD is not NULL.  */
>      char *pspace_exec_filename;
>  
> +    /* Nonzero if pspace_exec_filename was supplied by the user,
> +       either at startup (on the command-line) or via a "file"
> +       an "add-inferior -exec" command.  Zero if
> +       pspace_exec_filename is unset or was discovered by GDB
> +       somehow.  */
> +    int pspace_user_supplied_exec_file_p;
> +
>      /* The address space attached to this program space.  More than one
>         program space may be bound to the same address space.  In the
>         traditional unix-like debugging scenario, this will usually
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 099ddbb..b2f1bba 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -1556,9 +1556,10 @@ remote_add_inferior (int fake_pid_p, int pid, int attached,
>    inf->attach_flag = attached;
>    inf->fake_pid_p = fake_pid_p;
>  
> -  /* If no main executable is currently open then attempt to
> -     open the file that was executed to create this inferior.  */
> -  if (try_open_exec && !fake_pid_p && get_exec_file (0) == NULL)
> +  /* If the user did not explicitly specify an executable file
> +     then attempt to open the file that was executed to create
> +     this inferior.  */
> +  if (try_open_exec && !fake_pid_p && !user_supplied_exec_file_p)
>      exec_file_locate_attach (pid, 1);
>  
>    return inf;
> 

I realize that I am coming late to this discussion, sorry about that.

How does this interact with follow-exec-mode?  If follow-exec-mode is
'new' and the program execs, then 'run' will use the original executable
file.  But if follow-exec-mode is 'same' and the program execs, then
'run' will use the executable file that was active after the exec call.

In the follow-exec-mode == 'same' instance, is the assumption that the
exec'd executable file takes on the same 'user-supplied' attribute as
the initial executable, since it is using the original inferior?

If so, is there a scenario where:
 * the user supplies the exec file name
 * the program execs, so the exec file name is now different
 * then the user tries to do an attach (without an exec file name) to a
process running the original exec file, and gets the wrong exec file name?

Thanks
-Don