[Toybox] [PATCH] Fix hwclock -u.

[enh]

You can't pass a NULL value to setenv(3). The "put things back how they were"
intent of this code is best achieved by calling unsetenv(3) in the NULL case.

(This causes a crash with "hwclock -u" on Android. glibc silently corrupts the
environment instead.)
---
 lib/xwrap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/xwrap.c b/lib/xwrap.c
index 6d0c511..8a3ed6c 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -704,13 +704,13 @@ void xregcomp(regex_t *preg, char *regex, int cflags)

 char *xtzset(char *new)
 {
-  char *tz = getenv("TZ");
+  char *old = getenv("TZ");

-  if (tz) tz = xstrdup(tz);
-  if (setenv("TZ", new, 1)) perror_exit("setenv");
+  if (old) old = xstrdup(old);
+  if (new ? setenv("TZ", new, 1) : unsetenv("TZ")) perror_exit("setenv");
   tzset();

-  return tz;
+  return old;
 }

 // Set a signal handler
-- 
2.6.0.rc2.230.g3dd15c0
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