Always use errno > 0 to help gcc

gcc thinks that errno might be negative, and functions could return
something positive on error (-errno). Should not matter in practice,
but makes an -O4 build much quieter.

src/shared/calendarspec.c

@@ -391,7 +391,7 @@ static int prepend_component(const char **p, CalendarComponent **c) {
 
         errno = 0;
         value = strtoul(*p, &e, 10);
-        if (errno != 0)
+        if (errno > 0)
                 return -errno;
         if (e == *p)
                 return -EINVAL;
@@ -400,7 +400,7 @@ static int prepend_component(const char **p, CalendarComponent **c) {
 
         if (*e == '/') {
                 repeat = strtoul(e+1, &ee, 10);
-                if (errno != 0)
+                if (errno > 0)
                         return -errno;
                 if (ee == e+1)
                         return -EINVAL;

src/shared/fileio.c

@@ -364,7 +364,7 @@ int write_env_file(const char *fname, char **l) {
         fflush(f);
 
         if (ferror(f)) {
-                if (errno != 0)
+                if (errno > 0)
                         r = -errno;
                 else
                         r = -EIO;

src/shared/socket-util.c

@@ -68,7 +68,7 @@ int socket_address_parse(SocketAddress *a, const char *s) {
                 errno = 0;
                 if (inet_pton(AF_INET6, n, &a->sockaddr.in6.sin6_addr) <= 0) {
                         free(n);
-                        return errno != 0 ? -errno : -EINVAL;
+                        return errno > 0 ? -errno : -EINVAL;
                 }
 
                 free(n);

src/shared/time-util.c

@@ -547,7 +547,7 @@ int parse_usec(const char *t, usec_t *usec) {
                 errno = 0;
                 l = strtoll(p, &e, 10);
 
-                if (errno != 0)
+                if (errno > 0)
                         return -errno;
 
                 if (l < 0)
@@ -627,7 +627,7 @@ int parse_nsec(const char *t, nsec_t *nsec) {
                 errno = 0;
                 l = strtoll(p, &e, 10);
 
-                if (errno != 0)
+                if (errno > 0)
                         return -errno;
 
                 if (l < 0)

src/shared/util.c

@@ -2265,7 +2265,7 @@ int parse_bytes(const char *t, off_t *bytes) {
                 errno = 0;
                 l = strtoll(p, &e, 10);
 
-                if (errno != 0)
+                if (errno > 0)
                         return -errno;
 
                 if (l < 0)
@@ -4191,7 +4191,7 @@ int get_user_creds(
         }
 
         if (!p)
-                return errno != 0 ? -errno : -ESRCH;
+                return errno > 0 ? -errno : -ESRCH;
 
         if (uid)
                 *uid = p->pw_uid;
@@ -4272,7 +4272,7 @@ int get_group_creds(const char **groupname, gid_t *gid) {
         }
 
         if (!g)
-                return errno != 0 ? -errno : -ESRCH;
+                return errno > 0 ? -errno : -ESRCH;
 
         if (gid)
                 *gid = g->gr_gid;

src/shared/util.h

@@ -595,7 +595,7 @@ int create_tmp_dir(char template[], char** dir_name);
 #define FOREACH_DIRENT(de, d, on_error)                                 \
         for (errno = 0, de = readdir(d);; errno = 0, de = readdir(d))   \
                 if (!de) {                                              \
-                        if (errno != 0) {                               \
+                        if (errno > 0) {                                \
                                 on_error;                               \
                         }                                               \
                         break;                                          \