strv: Make sure strv_make_nulstr() always returns a valid nulstr

strv_make_nulstr() is documented to always return a valid nulstr,
but if the input is `NULL` we return a string terminated with only
a single NUL terminator, so let's fix that and always terminate the
resulting string with two NUL bytes.

diff --git a/src/basic/strv.c b/src/basic/strv.c
index eea34ca68d9a98f6317b190b5927f3536c40e7e6..24fc56a1a5cafcfbd53cdfdd92d7a8f4506da57b 100644 (file)
--- a/src/basic/strv.c
+++ b/src/basic/strv.c
@@ -721,7 +721,7 @@ int strv_make_nulstr(char * const *l, char **ret, size_t *ret_size) {
         }
 
         if (!m) {
-                m = new0(char, 1);
+                m = new0(char, 2);
                 if (!m)
                         return -ENOMEM;
                 n = 1;
@@ -730,11 +730,9 @@ int strv_make_nulstr(char * const *l, char **ret, size_t *ret_size) {
                 m[n] = '\0';
 
         assert(n > 0);
-        *ret = m;
+        *ret = TAKE_PTR(m);
         *ret_size = n - 1;
 
-        m = NULL;
-
         return 0;
 }