specifier: rework specifier calls to return proper error message

Previously the specifier calls could only indicate OOM by returning
NULL. With this change they will return negative errno-style error codes
like everything else.

13 files changed, 395 insertions, 238 deletions

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index f4a268c1ef..cfc6f078a6 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -99,9 +99,12 @@ int config_parse_unit_deps(const char* unit,
                 if (!t)
                         return log_oom();
 
-                k = unit_name_printf(u, t);
-                if (!k)
-                        return log_oom();
+                r = unit_name_printf(u, t, &k);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
+                                   "Failed to resolve specifiers, ignoring: %s", strerror(-r));
+                        continue;
+                }
 
                 r = unit_add_dependency_by_name(u, d, k, NULL, true);
                 if (r < 0)
@@ -124,16 +127,17 @@ int config_parse_unit_string_printf(const char *unit,
 
         Unit *u = userdata;
         _cleanup_free_ char *k = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
         assert(u);
 
-        k = unit_full_printf(u, rvalue);
-        if (!k)
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+        r = unit_full_printf(u, rvalue, &k);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
 
         return config_parse_string(unit, filename, line, section, lvalue, ltype,
                                    k ? k : rvalue, data, userdata);
@@ -151,16 +155,17 @@ int config_parse_unit_strv_printf(const char *unit,
 
         Unit *u = userdata;
         _cleanup_free_ char *k = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
         assert(u);
 
-        k = unit_full_printf(u, rvalue);
-        if (!k)
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+        r = unit_full_printf(u, rvalue, &k);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
 
         return config_parse_strv(unit, filename, line, section, lvalue, ltype,
                                  k ? k : rvalue, data, userdata);
@@ -178,16 +183,17 @@ int config_parse_unit_path_printf(const char *unit,
 
         Unit *u = userdata;
         _cleanup_free_ char *k = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
         assert(u);
 
-        k = unit_full_printf(u, rvalue);
-        if (!k)
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+        r = unit_full_printf(u, rvalue, &k);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
 
         return config_parse_path(unit, filename, line, section, lvalue, ltype,
                                  k ? k : rvalue, data, userdata);
@@ -205,6 +211,7 @@ int config_parse_socket_listen(const char *unit,
 
         SocketPort *p, *tail;
         Socket *s;
+        int r;
 
         assert(filename);
         assert(lvalue);
@@ -226,32 +233,31 @@ int config_parse_socket_listen(const char *unit,
         if (ltype != SOCKET_SOCKET) {
 
                 p->type = ltype;
-                p->path = unit_full_printf(UNIT(s), rvalue);
-                if (!p->path) {
+                r = unit_full_printf(UNIT(s), rvalue, &p->path);
+                if (r < 0) {
                         p->path = strdup(rvalue);
                         if (!p->path) {
                                 free(p);
                                 return log_oom();
                         } else
-                                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                           "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+                                log_syntax(unit, LOG_ERR, filename, line, -r,
+                                           "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
                 }
 
                 path_kill_slashes(p->path);
 
         } else if (streq(lvalue, "ListenNetlink")) {
                 _cleanup_free_ char  *k = NULL;
-                int r;
 
                 p->type = SOCKET_SOCKET;
-                k = unit_full_printf(UNIT(s), rvalue);
-                if (!k)
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                   "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+                r = unit_full_printf(UNIT(s), rvalue, &k);
+                if (r < 0)
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
+                                   "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
 
                 r = socket_address_parse_netlink(&p->address, k ? k : rvalue);
                 if (r < 0) {
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
                                    "Failed to parse address value, ignoring: %s", rvalue);
                         free(p);
                         return 0;
@@ -259,17 +265,16 @@ int config_parse_socket_listen(const char *unit,
 
         } else {
                 _cleanup_free_ char *k = NULL;
-                int r;
 
                 p->type = SOCKET_SOCKET;
-                k = unit_full_printf(UNIT(s), rvalue);
-                if (!k)
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                   "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+                r = unit_full_printf(UNIT(s), rvalue, &k);
+                if (r < 0)
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
+                                   "Failed to resolve unit specifiers on %s, ignoring: %s", rvalue, strerror(-r));
 
                 r = socket_address_parse(&p->address, k ? k : rvalue);
                 if (r < 0) {
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
                                    "Failed to parse address value, ignoring: %s", rvalue);
                         free(p);
                         return 0;
@@ -1230,11 +1235,12 @@ int config_parse_trigger_unit(
                 return 0;
         }
 
-        p = unit_name_printf(u, rvalue);
-        if (!p)
-                return log_oom();
+        r = unit_name_printf(u, rvalue, &p);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve specifiers, ignoring: %s", strerror(-r));
 
-        type = unit_name_to_type(p);
+        type = unit_name_to_type(p ?: rvalue);
         if (type < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, EINVAL,
                            "Unit type not valid, ignoring: %s", rvalue);
@@ -1247,10 +1253,10 @@ int config_parse_trigger_unit(
                 return 0;
         }
 
-        r = unit_add_two_dependencies_by_name(u, UNIT_BEFORE, UNIT_TRIGGERS, p, NULL, true);
+        r = unit_add_two_dependencies_by_name(u, UNIT_BEFORE, UNIT_TRIGGERS, p ?: rvalue, NULL, true);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, -r,
-                           "Failed to add trigger on %s, ignoring: %s", p, strerror(-r));
+                           "Failed to add trigger on %s, ignoring: %s", p ?: rvalue, strerror(-r));
                 return 0;
         }
 
@@ -1271,6 +1277,7 @@ int config_parse_path_spec(const char *unit,
         PathSpec *s;
         PathType b;
         _cleanup_free_ char *k = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
@@ -1290,13 +1297,13 @@ int config_parse_path_spec(const char *unit,
                 return 0;
         }
 
-        k = unit_full_printf(UNIT(p), rvalue);
-        if (!k) {
+        r = unit_full_printf(UNIT(p), rvalue, &k);
+        if (r < 0) {
                 k = strdup(rvalue);
                 if (!k)
                         return log_oom();
                 else
-                        log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
                                    "Failed to resolve unit specifiers on %s. Ignoring.",
                                    rvalue);
         }
@@ -1344,19 +1351,20 @@ int config_parse_socket_service(const char *unit,
 
         dbus_error_init(&error);
 
-        p = unit_name_printf(UNIT(s), rvalue);
-        if (!p)
-                return log_oom();
+        r = unit_name_printf(UNIT(s), rvalue, &p);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve specifiers, ignoring: %s", rvalue);
 
-        if (!endswith(p, ".service")) {
+        if (!endswith(p ?: rvalue, ".service")) {
                 log_syntax(unit, LOG_ERR, filename, line, EINVAL,
                            "Unit must be of type service, ignoring: %s", rvalue);
                 return 0;
         }
 
-        r = manager_load_unit(UNIT(s)->manager, p, NULL, &error, &x);
+        r = manager_load_unit(UNIT(s)->manager, p ?: rvalue, NULL, &error, &x);
         if (r < 0) {
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                log_syntax(unit, LOG_ERR, filename, line, r,
                            "Failed to load unit %s, ignoring: %s",
                            rvalue, bus_error(&error, r));
                 dbus_error_free(&error);
@@ -1395,23 +1403,24 @@ int config_parse_service_sockets(const char *unit,
                 if (!t)
                         return log_oom();
 
-                k = unit_name_printf(UNIT(s), t);
-                if (!k)
-                        return log_oom();
+                r = unit_name_printf(UNIT(s), t, &k);
+                if (r < 0)
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
+                                   "Failed to resolve specifiers, ignoring: %s", strerror(-r));
 
-                if (!endswith(k, ".socket")) {
+                if (!endswith(k ?: t, ".socket")) {
                         log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                                   "Unit must be of type socket, ignoring: %s", k);
+                                   "Unit must be of type socket, ignoring: %s", k ?: t);
                         continue;
                 }
 
-                r = unit_add_two_dependencies_by_name(UNIT(s), UNIT_WANTS, UNIT_AFTER, k, NULL, true);
+                r = unit_add_two_dependencies_by_name(UNIT(s), UNIT_WANTS, UNIT_AFTER, k ?: t, NULL, true);
                 if (r < 0)
                         log_syntax(unit, LOG_ERR, filename, line, -r,
                                    "Failed to add dependency on %s, ignoring: %s",
-                                   k, strerror(-r));
+                                   k ?: t, strerror(-r));
 
-                r = unit_add_dependency_by_name(UNIT(s), UNIT_TRIGGERED_BY, k, NULL, true);
+                r = unit_add_dependency_by_name(UNIT(s), UNIT_TRIGGERED_BY, k ?: t, NULL, true);
                 if (r < 0)
                         return r;
         }
@@ -1463,7 +1472,8 @@ int config_parse_unit_env_file(const char *unit,
 
         char ***env = data;
         Unit *u = userdata;
-        _cleanup_free_ char *s = NULL;
+        _cleanup_free_ char *n = NULL;
+        const char *s;
         int r;
 
         assert(filename);
@@ -1478,10 +1488,12 @@ int config_parse_unit_env_file(const char *unit,
                 return 0;
         }
 
-        s = unit_full_printf(u, rvalue);
-        if (!s)
-                return log_oom();
+        r = unit_full_printf(u, rvalue, &n);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, r,
+                           "Failed to resolve specifiers, ignoring: %s", rvalue);
 
+        s = n ?: rvalue;
         if (!path_is_absolute(s[0] == '-' ? s + 1 : s)) {
                 log_syntax(unit, LOG_ERR, filename, line, EINVAL,
                            "Path '%s' is not absolute, ignoring.", s);
@@ -1509,6 +1521,7 @@ int config_parse_environ(const char *unit,
         char*** env = data, *w, *state;
         size_t l;
         _cleanup_free_ char *k = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
@@ -1522,12 +1535,16 @@ int config_parse_environ(const char *unit,
                 return 0;
         }
 
-        if (u)
-                k = unit_full_printf(u, rvalue);
-        else
-                k = strdup(rvalue);
+        if (u) {
+                r = unit_full_printf(u, rvalue, &k);
+                if (r < 0)
+                        log_syntax(unit, LOG_ERR, filename, line, -r,
+                                   "Failed to resolve specifiers, ignoring: %s", rvalue);
+        }
 
         if (!k)
+                k = strdup(rvalue);
+        if (!k)
                 return log_oom();
 
         FOREACH_WORD_QUOTED(w, l, k, state) {
@@ -1598,6 +1615,7 @@ int config_parse_unit_condition_path(const char *unit,
         bool trigger, negate;
         Condition *c;
         _cleanup_free_ char *p = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
@@ -1619,9 +1637,15 @@ int config_parse_unit_condition_path(const char *unit,
         if (negate)
                 rvalue++;
 
-        p = unit_full_printf(u, rvalue);
-        if (!p)
-                return log_oom();
+        r = unit_full_printf(u, rvalue, &p);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve specifiers, ignoring: %s", rvalue);
+        if (!p) {
+                p = strdup(rvalue);
+                if (!p)
+                        return log_oom();
+        }
 
         if (!path_is_absolute(p)) {
                 log_syntax(unit, LOG_ERR, filename, line, EINVAL,
@@ -1652,6 +1676,7 @@ int config_parse_unit_condition_string(const char *unit,
         bool trigger, negate;
         Condition *c;
         _cleanup_free_ char *s = NULL;
+        int r;
 
         assert(filename);
         assert(lvalue);
@@ -1673,9 +1698,15 @@ int config_parse_unit_condition_string(const char *unit,
         if (negate)
                 rvalue++;
 
-        s = unit_full_printf(u, rvalue);
-        if (!s)
-                return log_oom();
+        r = unit_full_printf(u, rvalue, &s);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve specifiers, ignoring: %s", rvalue);
+        if (!s) {
+                s = strdup(rvalue);
+                if (!s)
+                        return log_oom();
+        }
 
         c = condition_new(cond, s, trigger, negate);
         if (!c)
@@ -1929,21 +1960,26 @@ int config_parse_unit_slice(
         assert(rvalue);
         assert(u);
 
-        k = unit_name_printf(u, rvalue);
-        if (!k)
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+        r = unit_name_printf(u, rvalue, &k);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, -r,
                            "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+        if (!k) {
+                k = strdup(rvalue);
+                if (!k)
+                        return log_oom();
+        }
 
-        r = manager_load_unit(u->manager, k ? k : rvalue, NULL, NULL, &slice);
+        r = manager_load_unit(u->manager, k, NULL, NULL, &slice);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, -r,
-                           "Failed to load slice unit %s. Ignoring.", k ? k : rvalue);
+                           "Failed to load slice unit %s. Ignoring.", k);
                 return 0;
         }
 
         if (slice->type != UNIT_SLICE) {
                 log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Slice unit %s is not a slice. Ignoring.", k ? k : rvalue);
+                           "Slice unit %s is not a slice. Ignoring.", k);
                 return 0;
         }
 
diff --git a/src/core/service.c b/src/core/service.c
index 246a86e23f..cc61b546fc 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -1765,11 +1765,9 @@ static int service_spawn(
         } else
                 unit_unwatch_timer(UNIT(s), &s->timer_watch);
 
-        argv = unit_full_printf_strv(UNIT(s), c->argv);
-        if (!argv) {
-                r = -ENOMEM;
+        r = unit_full_printf_strv(UNIT(s), c->argv, &argv);
+        if (r < 0)
                 goto fail;
-        }
 
         our_env = new0(char*, 5);
         if (!our_env) {
diff --git a/src/core/socket.c b/src/core/socket.c
index 2130e48686..46a73e0108 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1226,11 +1226,9 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {
         if (r < 0)
                 goto fail;
 
-        argv = unit_full_printf_strv(UNIT(s), c->argv);
-        if (!argv) {
-                r = -ENOMEM;
+        r = unit_full_printf_strv(UNIT(s), c->argv, &argv);
+        if (r < 0)
                 goto fail;
-        }
 
         r = exec_spawn(c,
                        argv,
diff --git a/src/core/unit-printf.c b/src/core/unit-printf.c
index ffc203dd92..1a29a986e9 100644
--- a/src/core/unit-printf.c
+++ b/src/core/unit-printf.c
@@ -30,98 +30,158 @@
 #include "cgroup-util.h"
 #include "special.h"
 
-static char *specifier_prefix_and_instance(char specifier, void *data, void *userdata) {
+static int specifier_prefix_and_instance(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n;
+
         assert(u);
 
-        return unit_name_to_prefix_and_instance(u->id);
+        n = unit_name_to_prefix_and_instance(u->id);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_prefix(char specifier, void *data, void *userdata) {
+static int specifier_prefix(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n;
+
         assert(u);
 
-        return unit_name_to_prefix(u->id);
+        n = unit_name_to_prefix(u->id);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_prefix_unescaped(char specifier, void *data, void *userdata) {
+static int specifier_prefix_unescaped(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
-        char *p, *r;
+        _cleanup_free_ char *p = NULL;
+        char *n;
 
         assert(u);
 
         p = unit_name_to_prefix(u->id);
         if (!p)
-                return NULL;
+                return -ENOMEM;
 
-        r = unit_name_unescape(p);
-        free(p);
+        n = unit_name_unescape(p);
+        if (!n)
+                return -ENOMEM;
 
-        return r;
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_instance_unescaped(char specifier, void *data, void *userdata) {
+static int specifier_instance_unescaped(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n;
+
         assert(u);
 
         if (u->instance)
-                return unit_name_unescape(u->instance);
+                n = unit_name_unescape(u->instance);
+        else
+                n = strdup("");
+
+        if (!n)
+                return -ENOMEM;
 
-        return strdup("");
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_filename(char specifier, void *data, void *userdata) {
+static int specifier_filename(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n;
+
         assert(u);
 
         if (u->instance)
-                return unit_name_path_unescape(u->instance);
+                n = unit_name_path_unescape(u->instance);
+        else
+                n = unit_name_to_path(u->id);
 
-        return unit_name_to_path(u->id);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_cgroup(char specifier, void *data, void *userdata) {
+static int specifier_cgroup(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n;
+
         assert(u);
 
-        return unit_default_cgroup_path(u);
+        n = unit_default_cgroup_path(u);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_cgroup_root(char specifier, void *data, void *userdata) {
-        _cleanup_free_ char *p = NULL;
+static int specifier_cgroup_root(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
         const char *slice;
+        char *n;
         int r;
 
         assert(u);
 
         slice = unit_slice_name(u);
         if (specifier == 'R' || !slice)
-                return strdup(u->manager->cgroup_root);
+                n = strdup(u->manager->cgroup_root);
+        else {
+                _cleanup_free_ char *p = NULL;
 
-        r = cg_slice_to_path(slice, &p);
-        if (r < 0)
-                return NULL;
+                r = cg_slice_to_path(slice, &p);
+                if (r < 0)
+                        return r;
+
+                n = strjoin(u->manager->cgroup_root, "/", p, NULL);
+                if (!n)
+                        return -ENOMEM;
+        }
 
-        return strjoin(u->manager->cgroup_root, "/", p, NULL);
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_runtime(char specifier, void *data, void *userdata) {
+static int specifier_runtime(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
+        char *n = NULL;
+
         assert(u);
 
         if (u->manager->running_as == SYSTEMD_USER) {
                 const char *e;
 
                 e = getenv("XDG_RUNTIME_DIR");
-                if (e)
-                        return strdup(e);
+                if (e) {
+                        n = strdup(e);
+                        if (!n)
+                                return -ENOMEM;
+                }
         }
 
-        return strdup("/run");
+        if (!n) {
+                n = strdup("/run");
+                if (!n)
+                        return -ENOMEM;
+        }
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_user_name(char specifier, void *data, void *userdata) {
+static int specifier_user_name(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
         ExecContext *c;
         int r;
@@ -143,26 +203,31 @@ static char *specifier_user_name(char specifier, void *data, void *userdata) {
         /* fish username from passwd */
         r = get_user_creds(&username, &uid, NULL, NULL, NULL);
         if (r < 0)
-                return NULL;
+                return r;
 
         switch (specifier) {
                 case 'U':
                         if (asprintf(&printed, "%d", uid) < 0)
-                                return NULL;
+                                return -ENOMEM;
                         break;
                 case 'u':
                         printed = strdup(username);
                         break;
         }
 
-        return printed;
+        if (!printed)
+                return -ENOMEM;
+
+        *ret = printed;
+        return 0;
 }
 
-static char *specifier_user_home(char specifier, void *data, void *userdata) {
+static int specifier_user_home(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
         ExecContext *c;
         int r;
         const char *username, *home;
+        char *n;
 
         assert(u);
 
@@ -174,25 +239,31 @@ static char *specifier_user_home(char specifier, void *data, void *userdata) {
 
                 r = get_home_dir(&h);
                 if (r < 0)
-                        return NULL;
+                        return r;
 
-                return h;
+                *ret = h;
+                return 0;
         }
 
         username = c->user;
         r = get_user_creds(&username, NULL, NULL, &home, NULL);
         if (r < 0)
-               return NULL;
+               return r;
 
-        return strdup(home);
+        n = strdup(home);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_user_shell(char specifier, void *data, void *userdata) {
+static int specifier_user_shell(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
         ExecContext *c;
         int r;
         const char *username, *shell;
-        char *ret;
+        char *n;
 
         assert(u);
 
@@ -205,27 +276,18 @@ static char *specifier_user_shell(char specifier, void *data, void *userdata) {
 
         /* return /bin/sh for root, otherwise the value from passwd */
         r = get_user_creds(&username, NULL, NULL, NULL, &shell);
-        if (r < 0) {
-                log_warning_unit(u->id,
-                                 "Failed to determine shell: %s",
-                                 strerror(-r));
-                return NULL;
-        }
-
-        if (!path_is_absolute(shell)) {
-                log_warning_unit(u->id,
-                                 "Shell %s is not absolute, ignoring.",
-                                 shell);
-        }
+        if (r < 0)
+                return r;
 
-        ret = strdup(shell);
-        if (!ret)
-                log_oom();
+        n = strdup(shell);
+        if (!n)
+                return -ENOMEM;
 
-        return ret;
+        *ret = n;
+        return 0;
 }
 
-char *unit_name_printf(Unit *u, const char* format) {
+int unit_name_printf(Unit *u, const char* format, char **ret) {
 
         /*
          * This will use the passed string as format string and
@@ -247,11 +309,12 @@ char *unit_name_printf(Unit *u, const char* format) {
 
         assert(u);
         assert(format);
+        assert(ret);
 
-        return specifier_printf(format, table, u);
+        return specifier_printf(format, table, u, ret);
 }
 
-char *unit_full_printf(Unit *u, const char *format) {
+int unit_full_printf(Unit *u, const char *format, char **ret) {
 
         /* This is similar to unit_name_printf() but also supports
          * unescaping. Also, adds a couple of additional codes:
@@ -296,14 +359,17 @@ char *unit_full_printf(Unit *u, const char *format) {
                 {}
         };
 
+        assert(u);
         assert(format);
+        assert(ret);
 
-        return specifier_printf(format, table, u);
+        return specifier_printf(format, table, u, ret);
 }
 
-char **unit_full_printf_strv(Unit *u, char **l) {
+int unit_full_printf_strv(Unit *u, char **l, char ***ret) {
         size_t n;
         char **r, **i, **j;
+        int q;
 
         /* Applies unit_full_printf to every entry in l */
 
@@ -312,22 +378,22 @@ char **unit_full_printf_strv(Unit *u, char **l) {
         n = strv_length(l);
         r = new(char*, n+1);
         if (!r)
-                return NULL;
+                return -ENOMEM;
 
         for (i = l, j = r; *i; i++, j++) {
-                *j = unit_full_printf(u, *i);
-                if (!*j)
+                q = unit_full_printf(u, *i, j);
+                if (q < 0)
                         goto fail;
         }
 
         *j = NULL;
-        return r;
+        *ret = r;
+        return 0;
 
 fail:
         for (j--; j >= r; j--)
                 free(*j);
 
         free(r);
-
-        return NULL;
+        return q;
 }
diff --git a/src/core/unit-printf.h b/src/core/unit-printf.h
index d2f4ccd178..51acad63e9 100644
--- a/src/core/unit-printf.h
+++ b/src/core/unit-printf.h
@@ -23,6 +23,6 @@
 
 #include "unit.h"
 
-char *unit_name_printf(Unit *u, const char* text);
-char *unit_full_printf(Unit *u, const char *text);
-char **unit_full_printf_strv(Unit *u, char **l);
+int unit_name_printf(Unit *u, const char* text, char **ret);
+int unit_full_printf(Unit *u, const char *text, char **ret);
+int unit_full_printf_strv(Unit *u, char **l, char ***ret);
diff --git a/src/shared/install-printf.c b/src/shared/install-printf.c
index 1157ea989b..1ee1243f4d 100644
--- a/src/shared/install-printf.c
+++ b/src/shared/install-printf.c
@@ -27,21 +27,35 @@
 #include "util.h"
 #include "install-printf.h"
 
-static char *specifier_prefix_and_instance(char specifier, void *data, void *userdata) {
+static int specifier_prefix_and_instance(char specifier, void *data, void *userdata, char **ret) {
         InstallInfo *i = userdata;
+        char *n;
+
         assert(i);
 
-        return unit_name_to_prefix_and_instance(i->name);
+        n = unit_name_to_prefix_and_instance(i->name);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_prefix(char specifier, void *data, void *userdata) {
+static int specifier_prefix(char specifier, void *data, void *userdata, char **ret) {
         InstallInfo *i = userdata;
+        char *n;
+
         assert(i);
 
-        return unit_name_to_prefix(i->name);
+        n = unit_name_to_prefix(i->name);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-static char *specifier_instance(char specifier, void *data, void *userdata) {
+static int specifier_instance(char specifier, void *data, void *userdata, char **ret) {
         InstallInfo *i = userdata;
         char *instance;
         int r;
@@ -50,14 +64,19 @@ static char *specifier_instance(char specifier, void *data, void *userdata) {
 
         r = unit_name_to_instance(i->name, &instance);
         if (r < 0)
-                return NULL;
-        if (instance != NULL)
-                return instance;
-        else
-                return strdup("");
+                return r;
+
+        if (!instance) {
+                instance = strdup("");
+                if (!instance)
+                        return -ENOMEM;
+        }
+
+        *ret = instance;
+        return 0;
 }
 
-static char *specifier_user_name(char specifier, void *data, void *userdata) {
+static int specifier_user_name(char specifier, void *data, void *userdata, char **ret) {
         InstallInfo *i = userdata;
         const char *username;
         _cleanup_free_ char *tmp = NULL;
@@ -82,18 +101,20 @@ static char *specifier_user_name(char specifier, void *data, void *userdata) {
 
                 r = get_user_creds(&username, &uid, NULL, NULL, NULL);
                 if (r < 0)
-                        return NULL;
+                        return r;
 
                 if (asprintf(&printed, "%d", uid) < 0)
-                        return NULL;
+                        return -ENOMEM;
                 break;
         }}
 
-        return printed;
+
+        *ret = printed;
+        return 0;
 }
 
 
-char *install_full_printf(InstallInfo *i, const char *format) {
+int install_full_printf(InstallInfo *i, const char *format, char **ret) {
 
         /* This is similar to unit_full_printf() but does not support
          * anything path-related.
@@ -129,6 +150,7 @@ char *install_full_printf(InstallInfo *i, const char *format) {
 
         assert(i);
         assert(format);
+        assert(ret);
 
-        return specifier_printf(format, table, i);
+        return specifier_printf(format, table, i, ret);
 }
diff --git a/src/shared/install-printf.h b/src/shared/install-printf.h
index 46f5294d21..6ffa488b1b 100644
--- a/src/shared/install-printf.h
+++ b/src/shared/install-printf.h
@@ -22,4 +22,4 @@
 #pragma once
 
 #include "install.h"
-char *install_full_printf(InstallInfo *i, const char *format);
+int install_full_printf(InstallInfo *i, const char *format, char **ret);
diff --git a/src/shared/install.c b/src/shared/install.c
index 07e06c425f..9722ed4e1c 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -967,14 +967,15 @@ static int config_parse_user(const char *unit,
 
         InstallInfo *i = data;
         char* printed;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
 
-        printed = install_full_printf(i, rvalue);
-        if (!printed)
-                return -ENOMEM;
+        r = install_full_printf(i, rvalue, &printed);
+        if (r < 0)
+                return r;
 
         free(i->user);
         i->user = printed;
@@ -1200,9 +1201,9 @@ static int install_info_symlink_alias(
         STRV_FOREACH(s, i->aliases) {
                 _cleanup_free_ char *alias_path = NULL, *dst = NULL;
 
-                dst = install_full_printf(i, *s);
-                if (!dst)
-                        return -ENOMEM;
+                q = install_full_printf(i, *s, &dst);
+                if (q < 0)
+                        return q;
 
                 alias_path = path_make_absolute(dst, config_path);
                 if (!alias_path)
@@ -1232,9 +1233,9 @@ static int install_info_symlink_wants(
         STRV_FOREACH(s, i->wanted_by) {
                 _cleanup_free_ char *path = NULL, *dst = NULL;
 
-                dst = install_full_printf(i, *s);
-                if (!dst)
-                        return -ENOMEM;
+                q = install_full_printf(i, *s, &dst);
+                if (q < 0)
+                        return q;
 
                 if (!unit_name_is_valid(dst, true)) {
                         r = -EINVAL;
@@ -1269,9 +1270,9 @@ static int install_info_symlink_requires(
         STRV_FOREACH(s, i->required_by) {
                 _cleanup_free_ char *path = NULL, *dst = NULL;
 
-                dst = install_full_printf(i, *s);
-                if (!dst)
-                        return -ENOMEM;
+                q = install_full_printf(i, *s, &dst);
+                if (q < 0)
+                        return q;
 
                 if (!unit_name_is_valid(dst, true)) {
                         r = -EINVAL;
diff --git a/src/shared/specifier.c b/src/shared/specifier.c
index bb8859fdfd..8fbf6db5df 100644
--- a/src/shared/specifier.c
+++ b/src/shared/specifier.c
@@ -32,21 +32,22 @@
  *
  */
 
-char *specifier_printf(const char *text, const Specifier table[], void *userdata) {
-        char *r, *t;
+int specifier_printf(const char *text, const Specifier table[], void *userdata, char **_ret) {
+        char *ret, *t;
         const char *f;
         bool percent = false;
         size_t l;
+        int r;
 
         assert(text);
         assert(table);
 
         l = strlen(text);
-        r = new(char, l+1);
-        if (!r)
-                return NULL;
+        ret = new(char, l+1);
+        if (!ret)
+                return -ENOMEM;
 
-        t = r;
+        t = ret;
 
         for (f = text; *f; f++, l--) {
 
@@ -61,32 +62,31 @@ char *specifier_printf(const char *text, const Specifier table[], void *userdata
                                                 break;
 
                                 if (i->lookup) {
-                                        char *n, *w;
+                                        _cleanup_free_ char *w = NULL;
+                                        char *n;
                                         size_t k, j;
 
-                                        w = i->lookup(i->specifier, i->data, userdata);
-                                        if (!w) {
-                                                free(r);
-                                                return NULL;
+                                        r = i->lookup(i->specifier, i->data, userdata, &w);
+                                        if (r < 0) {
+                                                free(ret);
+                                                return r;
                                         }
 
-                                        j = t - r;
+                                        j = t - ret;
                                         k = strlen(w);
 
                                         n = new(char, j + k + l + 1);
                                         if (!n) {
-                                                free(r);
-                                                free(w);
-                                                return NULL;
+                                                free(ret);
+                                                return -ENOMEM;
                                         }
 
-                                        memcpy(n, r, j);
+                                        memcpy(n, ret, j);
                                         memcpy(n + j, w, k);
 
-                                        free(r);
-                                        free(w);
+                                        free(ret);
 
-                                        r = n;
+                                        ret = n;
                                         t = n + j + k;
                                 } else {
                                         *(t++) = '%';
@@ -102,58 +102,81 @@ char *specifier_printf(const char *text, const Specifier table[], void *userdata
         }
 
         *t = 0;
-        return r;
+        *_ret = ret;
+        return 0;
 }
 
 /* Generic handler for simple string replacements */
 
-char* specifier_string(char specifier, void *data, void *userdata) {
-        return strdup(strempty(data));
+int specifier_string(char specifier, void *data, void *userdata, char **ret) {
+        char *n;
+
+        n = strdup(strempty(data));
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-char *specifier_machine_id(char specifier, void *data, void *userdata) {
+int specifier_machine_id(char specifier, void *data, void *userdata, char **ret) {
         sd_id128_t id;
-        char *buf;
+        char *n;
         int r;
 
         r = sd_id128_get_machine(&id);
         if (r < 0)
-                return NULL;
+                return r;
 
-        buf = new(char, 33);
-        if (!buf)
-                return NULL;
+        n = new(char, 33);
+        if (!n)
+                return -ENOMEM;
 
-        return sd_id128_to_string(id, buf);
+        *ret = sd_id128_to_string(id, n);
+        return 0;
 }
 
-char *specifier_boot_id(char specifier, void *data, void *userdata) {
+int specifier_boot_id(char specifier, void *data, void *userdata, char **ret) {
         sd_id128_t id;
-        char *buf;
+        char *n;
         int r;
 
         r = sd_id128_get_boot(&id);
         if (r < 0)
-                return NULL;
+                return r;
 
-        buf = new(char, 33);
-        if (!buf)
-                return NULL;
+        n = new(char, 33);
+        if (!n)
+                return -ENOMEM;
 
-        return sd_id128_to_string(id, buf);
+        *ret = sd_id128_to_string(id, n);
+        return 0;
 }
 
-char *specifier_host_name(char specifier, void *data, void *userdata) {
-        return gethostname_malloc();
+int specifier_host_name(char specifier, void *data, void *userdata, char **ret) {
+        char *n;
+
+        n = gethostname_malloc();
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
 }
 
-char *specifier_kernel_release(char specifier, void *data, void *userdata) {
+int specifier_kernel_release(char specifier, void *data, void *userdata, char **ret) {
         struct utsname uts;
+        char *n;
         int r;
 
         r = uname(&uts);
         if (r < 0)
-                return NULL;
+                return -errno;
+
+        n = strdup(uts.release);
+        if (!n)
+                return -ENOMEM;
 
-        return strdup(uts.release);
+        *ret = n;
+        return 0;
 }
diff --git a/src/shared/specifier.h b/src/shared/specifier.h
index d13e6406b6..fca206f665 100644
--- a/src/shared/specifier.h
+++ b/src/shared/specifier.h
@@ -21,7 +21,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-typedef char* (*SpecifierCallback)(char specifier, void *data, void *userdata);
+typedef int (*SpecifierCallback)(char specifier, void *data, void *userdata, char **ret);
 
 typedef struct Specifier {
         const char specifier;
@@ -29,11 +29,11 @@ typedef struct Specifier {
         void *data;
 } Specifier;
 
-char *specifier_printf(const char *text, const Specifier table[], void *userdata);
+int specifier_printf(const char *text, const Specifier table[], void *userdata, char **ret);
 
-char *specifier_string(char specifier, void *data, void *userdata);
+int specifier_string(char specifier, void *data, void *userdata, char **ret);
 
-char *specifier_machine_id(char specifier, void *data, void *userdata);
-char *specifier_boot_id(char specifier, void *data, void *userdata);
-char *specifier_host_name(char specifier, void *data, void *userdata);
-char *specifier_kernel_release(char specifier, void *data, void *userdata);
+int specifier_machine_id(char specifier, void *data, void *userdata, char **ret);
+int specifier_boot_id(char specifier, void *data, void *userdata, char **ret);
+int specifier_host_name(char specifier, void *data, void *userdata, char **ret);
+int specifier_kernel_release(char specifier, void *data, void *userdata, char **ret);
diff --git a/src/test/test-strv.c b/src/test/test-strv.c
index 25bee22dfe..6513d2e07b 100644
--- a/src/test/test-strv.c
+++ b/src/test/test-strv.c
@@ -28,18 +28,30 @@
 
 static void test_specifier_printf(void) {
         _cleanup_free_ char *w = NULL;
+        int r;
 
         const Specifier table[] = {
                 { 'a', specifier_string, (char*) "AAAA" },
                 { 'b', specifier_string, (char*) "BBBB" },
+                { 'm', specifier_machine_id, NULL },
+                { 'B', specifier_boot_id, NULL },
+                { 'H', specifier_host_name, NULL },
+                { 'v', specifier_kernel_release, NULL },
                 { 0, NULL, NULL }
         };
 
-        w = specifier_printf("xxx a=%a b=%b yyy", table, NULL);
+        r = specifier_printf("xxx a=%a b=%b yyy", table, NULL, &w);
+        assert_se(r >= 0);
+        assert_se(w);
+
         puts(w);
+        assert_se(streq(w, "xxx a=AAAA b=BBBB yyy"));
 
+        free(w);
+        r = specifier_printf("machine=%m, boot=%B, host=%H, version=%v", table, NULL, &w);
+        assert_se(r >= 0);
         assert_se(w);
-        assert_se(streq(w, "xxx a=AAAA b=BBBB yyy"));
+        puts(w);
 }
 
 static const char* const input_table_multiple[] = {
diff --git a/src/test/test-unit-file.c b/src/test/test-unit-file.c
index dc6bc55244..0413ae2117 100644
--- a/src/test/test-unit-file.c
+++ b/src/test/test-unit-file.c
@@ -302,17 +302,18 @@ static void test_install_printf(void) {
 
         _cleanup_free_ char *mid, *bid, *host;
 
-        assert_se((mid = specifier_machine_id('m', NULL, NULL)));
-        assert_se((bid = specifier_boot_id('b', NULL, NULL)));
+        assert_se(specifier_machine_id('m', NULL, NULL, &mid) >= 0 && mid);
+        assert_se(specifier_boot_id('b', NULL, NULL, &bid) >= 0 && bid);
         assert_se((host = gethostname_malloc()));
 
 #define expect(src, pattern, result)                                    \
         do {                                                            \
-                _cleanup_free_ char *t = install_full_printf(&src, pattern); \
+                _cleanup_free_ char *t = NULL;                          \
                 _cleanup_free_ char                                     \
                         *d1 = strdup(i.name),                           \
                         *d2 = strdup(i.path),                           \
                         *d3 = strdup(i.user);                           \
+                assert_se(install_full_printf(&src, pattern, &t) >= 0 || !result); \
                 memzero(i.name, strlen(i.name));                        \
                 memzero(i.path, strlen(i.path));                        \
                 memzero(i.user, strlen(i.user));                        \
diff --git a/src/test/test-unit-name.c b/src/test/test-unit-name.c
index c17692b845..67ccdd4228 100644
--- a/src/test/test-unit-name.c
+++ b/src/test/test-unit-name.c
@@ -117,8 +117,8 @@ static int test_unit_printf(void) {
         _cleanup_free_ char *mid, *bid, *host, *root_uid;
         struct passwd *root;
 
-        assert_se((mid = specifier_machine_id('m', NULL, NULL)));
-        assert_se((bid = specifier_boot_id('b', NULL, NULL)));
+        assert_se(specifier_machine_id('m', NULL, NULL, &mid) >= 0 && mid);
+        assert_se(specifier_boot_id('b', NULL, NULL, &bid) >= 0 && bid);
         assert_se((host = gethostname_malloc()));
 
         assert_se((root = getpwnam("root")));
@@ -134,8 +134,8 @@ static int test_unit_printf(void) {
 #define expect(unit, pattern, expected)                                 \
         {                                                               \
                 char *e;                                                \
-                _cleanup_free_ char *t =                                \
-                        unit_full_printf(unit, pattern);                \
+                _cleanup_free_ char *t;                                 \
+                assert_se(unit_full_printf(unit, pattern, &t) >= 0);    \
                 printf("result: %s\nexpect: %s\n", t, expected);        \
                 if ((e = endswith(expected, "*")))                      \
                         assert(strncmp(t, e, e-expected));              \