PATH defaults now act more like GNU and POSIX

When PATH is unset or empty, use the system default,
to be consistent with GNU/Linux and with POSIX.
If there is no system default do not default to "."
as that can be dangerous.
* src/callproc.c (init_callproc_1, init_callproc):
Default PATH to the null pointer, not the empty string.
* src/emacs.c (default_PATH): New function.
(find_emacs_executable, decode_env_path): Be consistent with POSIX
and with glibc about what to do when PATH is unset or empty.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/callproc.c b/src/callproc.c
index 7059a2bac6f..e1a369b47f4 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1960,7 +1960,7 @@ init_callproc_1 (void)
   Vexec_path = decode_env_path ("EMACSPATH", PATH_EXEC, 0);
   Vexec_directory = Ffile_name_as_directory (Fcar (Vexec_path));
   /* FIXME?  For ns, path_exec should go at the front?  */
-  Vexec_path = nconc2 (decode_env_path ("PATH", "", 0), Vexec_path);
+  Vexec_path = nconc2 (decode_env_path ("PATH", NULL, 0), Vexec_path);
 }
 
 /* This is run after init_cmdargs, when Vinstallation_directory is valid.  */
@@ -1985,7 +1985,7 @@ init_callproc (void)
         {
           /* Running uninstalled, so default to tem rather than PATH_EXEC.  */
           Vexec_path = decode_env_path ("EMACSPATH", SSDATA (tem), 0);
-          Vexec_path = nconc2 (decode_env_path ("PATH", "", 0), Vexec_path);
+          Vexec_path = nconc2 (decode_env_path ("PATH", NULL, 0), Vexec_path);
         }
 
       Vexec_directory = Ffile_name_as_directory (tem);