Re: PWD not made canonical on shell start

[dualbus]

On Mon, May 29, 2017 at 06:25:06PM -0400, Chet Ramey wrote:
[...]
> If PWD appears in the environment, and it is an absolute pathname of the
> CWD, set PWD to the canonicalized version of the environment value. The
> canonicalized version removes . and .., makes sure that the length is
> less than PATH_MAX, and validates that at each step, removing . and ..
> results in a valid pathname. If canonicalization fails, PWD gets the value
> that would be printed by pwd -P if PWD were not set.

That's not quite true. In variables.c `set_pwd', there's the following:

 843   temp_var = find_variable ("PWD");
 844   /* Follow posix rules for importing PWD */
 845   if (temp_var && imported_p (temp_var) &&
 846       (temp_string = value_cell (temp_var)) &&
 847       temp_string[0] == '/' &&
 848       same_file (temp_string, ".", (struct stat *)NULL, (struct stat 
*)NULL))
 849     {
 850       current_dir = sh_canonpath (temp_string, 
PATH_CHECKDOTDOT|PATH_CHECKEXISTS);
 851       if (current_dir == 0)
 852         current_dir = get_working_directory ("shell_init");
 853       else
 854         set_working_directory (current_dir);
 855       free (current_dir);
 856     }

`current_dir' is a copy of `temp_string' which holds the canonicalized version
of the environment value. That's true. *But* PWD is not re-set to the value of
`current_dir'. Instead, it has the same value as passed through the
environment (i.e. `temp_string').

For completeness, in builtins/common.c `set_working_directory' just updates a
global variable, but doesn't touch the value of the PWD variable.

 589 /* Make NAME our internal idea of the current working directory. */
 590 void
 591 set_working_directory (name)
 592      char *name;
 593 {  
 594   FREE (the_current_working_directory);
 595   the_current_working_directory = savestring (name);
 596 } 

Hence, my initial patch:

diff --git a/variables.c b/variables.c
index 944de86e..62f9f229 100644
--- a/variables.c
+++ b/variables.c
@@ -852,6 +852,8 @@ set_pwd ()
        current_dir = get_working_directory ("shell_init");
       else 
        set_working_directory (current_dir);
+      temp_var = bind_variable ("PWD", current_dir);
+      set_auto_export (temp_var);
       free (current_dir);
     }
   else if (home_string && interactive_shell && login_shell &&