tree-wide: introduce mfree()

Pretty trivial helper which wraps free() but returns NULL, so we can
simplify this:
        free(foobar);
        foobar = NULL;
to this:
        foobar = mfree(foobar);

3 files changed, 3 insertions, 6 deletions

diff --git a/src/journal/catalog.c b/src/journal/catalog.c
index 33b0539315..a3e51e2f52 100644
--- a/src/journal/catalog.c
+++ b/src/journal/catalog.c
@@ -263,8 +263,7 @@ int catalog_import_file(Hashmap *h, struct strbuf *sb, const char *path) {
                                         if (r < 0)
                                                 return r;
 
-                                        free(lang);
-                                        lang = NULL;
+                                        lang = mfree(lang);
                                 }
 
                                 if (with_language) {
diff --git a/src/journal/coredumpctl.c b/src/journal/coredumpctl.c
index fc49b2e174..098f62af50 100644
--- a/src/journal/coredumpctl.c
+++ b/src/journal/coredumpctl.c
@@ -587,8 +587,7 @@ static int save_core(sd_journal *j, int fd, char **path, bool *unlink_temp) {
         if (filename && access(filename, R_OK) < 0) {
                 log_full(errno == ENOENT ? LOG_DEBUG : LOG_WARNING,
                          "File %s is not readable: %m", filename);
-                free(filename);
-                filename = NULL;
+                filename = mfree(filename);
         }
 
         if (filename && !endswith(filename, ".xz") && !endswith(filename, ".lz4")) {
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 073cc77711..355c4f1ee3 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -1259,8 +1259,7 @@ static int add_units(sd_journal *j) {
                 }
         }
 
-        strv_free(patterns);
-        patterns = NULL;
+        patterns = strv_free(patterns);
 
         STRV_FOREACH(i, arg_user_units) {
                 _cleanup_free_ char *u = NULL;