macro: introduce POINTER_MAX as define for (void*) -1

Just add a safer, prettier way to write (void*) -1, that doesn't rely on
two's complement, but uses the correct underlying C constructs.

src/basic/macro.h

@@ -554,10 +554,13 @@ static inline int __coverity_check_and_return__(int condition) {
 #define STRV_MAKE(...) ((char**) ((const char*[]) { __VA_ARGS__, NULL }))
 #define STRV_MAKE_EMPTY ((char*[1]) { NULL })
 
-/* Iterates through a specified list of pointers. Accepts NULL pointers, but uses (void*) -1 as internal marker for EOL. */
-#define FOREACH_POINTER(p, x, ...)                                                      \
-        for (typeof(p) *_l = (typeof(p)[]) { ({ p = x; }), ##__VA_ARGS__, (void*) -1 }; \
-             p != (typeof(p)) (void*) -1;                                               \
+/* Pointers range from NULL to POINTER_MAX */
+#define POINTER_MAX ((void*) UINTPTR_MAX)
+
+/* Iterates through a specified list of pointers. Accepts NULL pointers, but uses POINTER_MAX as internal marker for EOL. */
+#define FOREACH_POINTER(p, x, ...)                                                       \
+        for (typeof(p) *_l = (typeof(p)[]) { ({ p = x; }), ##__VA_ARGS__, POINTER_MAX }; \
+             p != (typeof(p)) POINTER_MAX;                                               \
              p = *(++_l))
 
 /* Define C11 thread_local attribute even on older gcc compiler

src/basic/path-util.c

@@ -550,7 +550,7 @@ char* path_join_internal(const char *first, ...) {
 
         sz = strlen_ptr(first);
         va_start(ap, first);
-        while ((p = va_arg(ap, char*)) != (const char*) -1)
+        while ((p = va_arg(ap, char*)) != POINTER_MAX)
                 if (!isempty(p))
                         sz += 1 + strlen(p);
         va_end(ap);
@@ -570,7 +570,7 @@ char* path_join_internal(const char *first, ...) {
         }
 
         va_start(ap, first);
-        while ((p = va_arg(ap, char*)) != (const char*) -1) {
+        while ((p = va_arg(ap, char*)) != POINTER_MAX) {
                 if (isempty(p))
                         continue;
 

src/basic/path-util.h

@@ -62,7 +62,7 @@ int path_compare(const char *a, const char *b) _pure_;
 bool path_equal(const char *a, const char *b) _pure_;
 bool path_equal_or_files_same(const char *a, const char *b, int flags);
 char* path_join_internal(const char *first, ...);
-#define path_join(x, ...) path_join_internal(x, __VA_ARGS__, (const char*) -1)
+#define path_join(x, ...) path_join_internal(x, __VA_ARGS__, POINTER_MAX)
 
 char* path_simplify(char *path, bool kill_dots);
 

src/basic/strv.h

@@ -62,7 +62,7 @@ char **strv_new_internal(const char *x, ...) _sentinel_;
 char **strv_new_ap(const char *x, va_list ap);
 #define strv_new(...) strv_new_internal(__VA_ARGS__, NULL)
 
-#define STRV_IGNORE ((const char *) -1)
+#define STRV_IGNORE ((const char *) POINTER_MAX)
 
 static inline const char* STRV_IFNOTNULL(const char *x) {
         return x ? x : STRV_IGNORE;

src/home/pam_systemd_home.c

@@ -142,7 +142,7 @@ static int acquire_user_record(
         if (r == PAM_SUCCESS && json) {
                 /* We determined earlier that this is not a homed user? Then exit early. (We use -1 as
                  * negative cache indicator) */
-                if (json == (void*) -1)
+                if (json == POINTER_MAX)
                         return PAM_USER_UNKNOWN;
         } else {
                 _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
@@ -235,7 +235,7 @@ static int acquire_user_record(
 
 user_unknown:
         /* Cache this, so that we don't check again */
-        r = pam_set_data(handle, homed_field, (void*) -1, NULL);
+        r = pam_set_data(handle, homed_field, POINTER_MAX, NULL);
         if (r != PAM_SUCCESS)
                 pam_syslog(handle, LOG_ERR, "Failed to set PAM user record data '%s' to invalid, ignoring: %s",
                            homed_field, pam_strerror(handle, r));

src/shared/json.c

@@ -3892,7 +3892,7 @@ int json_dispatch(JsonVariant *v, const JsonDispatch table[], JsonDispatchCallba
                 assert_se(value = json_variant_by_index(v, i+1));
 
                 for (p = table; p->name; p++)
-                        if (p->name == (const char*) -1 ||
+                        if (p->name == POINTER_MAX ||
                             streq_ptr(json_variant_string(key), p->name))
                                 break;