Re: env

[Jim Meyering]

Harvey Eneman <address@hidden> wrote:
> I've experienced an issue with the env implementation due to its
> modification of the environ external variable:
>
>  /* If no program is specified, print the environment and exit. */
>  if (argc <= optind)
>    {
>      while (*environ)
>         puts (*environ++);
>      exit (EXIT_SUCCESS);
>    }
>
> The difficulty occurs when a LD_PRELOAD shared object uses glib
> functions that rely in the stability of environ.

Thanks for the report and patch.
Which functions are those?

> Is there a rational reason why a local variable is not being used?  For
> example:
>
>  /* If no program is specified, print the environment and exit. */
>  if (argc <= optind)
>    {
>      char **e = environ;
>      while (*e)
>         puts (*e++);
>      exit (EXIT_SUCCESS);
>    }

Here's the likely change:

        * src/env.c (main): When invoked with no arguments (i.e. when printing
        the environment), use a local variable to iterate through the global
        "environ" array, rather than "environ" itself.  This is solely to
        avoid changing the environment for an LD_PRELOAD-substituted "puts"
        or "exit" function.  Tiny patch by Harvey Eneman.  See
        <http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/9735>.

diff --git a/src/env.c b/src/env.c
index 7283926..f2dc5f1 100644
--- a/src/env.c
+++ b/src/env.c
@@ -189,8 +189,9 @@ main (int argc, char **argv)
   /* If no program is specified, print the environment and exit. */
   if (argc <= optind)
     {
-      while (*environ)
-       puts (*environ++);
+      char const **e = environ;
+      while (*e)
+       puts (*e++);
       exit (EXIT_SUCCESS);
     }