ash: export certain variables to the environment immediately

The environment variables BB_OVERRIDE_APPLETS, BB_SKIP_ANSI_EMULATION
and BB_SYSTEMROOT affect of the behaviour of the shell itself.
Setting them as shell variables is insufficient for them to affect
the current shell.

When these three variables are exported from the shell they are
now placed in the environment immediately.  Conversely, when
they're unset or unexported they're removed from the environment.

2 files changed, 12 insertions, 2 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 8d58ce2ea..9e415610d 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -268,7 +268,7 @@ int FAST_FUNC is_applet_preferred(const char *name)
         const char *var, *s;
         size_t len;
 
-        var = getenv("BB_OVERRIDE_APPLETS");
+        var = getenv(BB_OVERRIDE_APPLETS);
         if (var && *var) {
                 /* '-' overrides all applets */
                 if (var[0] == '-' && var[1] == '\0')
diff --git a/libbb/messages.c b/libbb/messages.c
index 04863855a..e35bf8c6b 100644
--- a/libbb/messages.c
+++ b/libbb/messages.c
@@ -30,7 +30,17 @@ const char bb_hexdigits_upcase[] ALIGN1 = "0123456789ABCDEF";
 #if !ENABLE_PLATFORM_MINGW32
 const char bb_busybox_exec_path[] ALIGN1 = CONFIG_BUSYBOX_EXEC_PATH;
 #else
-const char bb_skip_ansi_emulation[] ALIGN1 = "BB_SKIP_ANSI_EMULATION";
+/* Some special shell variables are placed in the environment immediately
+ * when they're exported.
+ *
+ * BB_GLOBBING and BB_UMASK are excluded because users shouln't be
+ * messing with them; BB_ALT_BUFFER and BB_FIX_BACKSLASH are excluded
+ * because they only affect particular applets, not the shell itself.
+ */
+const char bbvar[] ALIGN1 =
+                "BB_OVERRIDE_APPLETS\0" \
+                "BB_SKIP_ANSI_EMULATION\0" \
+                "BB_SYSTEMROOT\0";
 #endif
 const char bb_default_login_shell[] ALIGN1 = LIBBB_DEFAULT_LOGIN_SHELL;
 /* util-linux manpage says /sbin:/bin:/usr/sbin:/usr/bin,