basic: introduce *_to_string_with_check() functions

They are used in later commits.

src/basic/errno-list.h

@@ -20,6 +20,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <stdbool.h>
 /*
  * MAX_ERRNO is defined as 4095 in linux/err.h
  * We use the same value here.
@@ -28,3 +29,6 @@
 
 const char *errno_to_name(int id);
 int errno_from_name(const char *name);
+static inline bool errno_is_valid(int n) {
+        return n > 0 && n <= ERRNO_MAX;
+}

src/basic/parse-util.c

@@ -283,7 +283,8 @@ int parse_errno(const char *t) {
         if (r < 0)
                 return r;
 
-        if (e < 0 || e > ERRNO_MAX)
+        /* 0 is also allowed here */
+        if (!errno_is_valid(e) && e != 0)
                 return -ERANGE;
 
         return e;

src/basic/process-util.h

@@ -137,6 +137,13 @@ static inline bool pid_is_valid(pid_t p) {
         return p > 0;
 }
 
+static inline int sched_policy_to_string_alloc_with_check(int n, char **s) {
+        if (!sched_policy_is_valid(n))
+                return -EINVAL;
+
+        return sched_policy_to_string_alloc(n, s);
+}
+
 int ioprio_parse_priority(const char *s, int *ret);
 
 pid_t getpid_cached(void);

src/basic/securebits-util.h

@@ -24,6 +24,14 @@
 
 int secure_bits_to_string_alloc(int i, char **s);
 int secure_bits_from_string(const char *s);
+
 static inline bool secure_bits_is_valid(int i) {
         return ((SECURE_ALL_BITS | SECURE_ALL_LOCKS) & i) == i;
 }
+
+static inline int secure_bits_to_string_alloc_with_check(int n, char **s) {
+        if (!secure_bits_is_valid(n))
+                return -EINVAL;
+
+        return secure_bits_to_string_alloc(n, s);
+}

src/basic/signal-util.h

@@ -55,3 +55,10 @@ static inline void block_signals_reset(sigset_t *ss) {
 static inline bool SIGNAL_VALID(int signo) {
         return signo > 0 && signo < _NSIG;
 }
+
+static inline const char* signal_to_string_with_check(int n) {
+        if (!SIGNAL_VALID(n))
+                return NULL;
+
+        return signal_to_string(n);
+}