Warn about unused return values that are quite important.

* CI: ArchLinux build should now instrument `-Werror`
 * CI: Increased OpenWrt build verbosity

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

.github/workflows/build-archlinux.yml

@@ -15,6 +15,8 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    env:
+      CMAKE_C_FLAGS: -Werror
     steps:
       - uses: actions/checkout@v3
         with:

.github/workflows/build-openwrt.yml

@@ -57,6 +57,7 @@ jobs:
           FEED_DIR: ${{ github.workspace }}/packages/openwrt
           FEEDNAME: ndpid_openwrt_packages_ci
           PACKAGES: nDPId-testing
+          V: s
 
       - name: Store packages
         uses: actions/upload-artifact@v3

nDPId-test.c

@@ -1557,7 +1557,11 @@ static int nio_selftest()
 
     char const wbuf[] = "AAAA";
     size_t const wlen = strnlen(wbuf, sizeof(wbuf));
-    write(pipefds[1], wbuf, wlen);
+    if (write(pipefds[1], wbuf, wlen) < 0)
+    {
+        logger(1, "Write '%s' (%zu bytes) to pipe failed with: %s", wbuf, wlen, strerror(errno));
+        goto error;
+    }
 
     if (nio_run(&io, 1000) != NIO_SUCCESS)
     {

nDPId.c

@@ -89,6 +89,8 @@
         name.var = value;                                                                                              \
         pthread_mutex_init(&name.var_mutex, NULL);                                                                     \
     } while (0)
+
+WARN_UNUSED
 static inline uint64_t mt_pt_get_and_add(volatile uint64_t * value, uint64_t add, pthread_mutex_t * mutex)
 {
     uint64_t result;
@@ -98,7 +100,10 @@ static inline uint64_t mt_pt_get_and_add(volatile uint64_t * value, uint64_t add
     pthread_mutex_unlock(mutex);
     return result;
 }
+
 #define MT_GET_AND_ADD(name, value) mt_pt_get_and_add(&name.var, value, &name.var_mutex)
+
+WARN_UNUSED
 static inline uint64_t mt_pt_get_and_sub(volatile uint64_t * value, uint64_t sub, pthread_mutex_t * mutex)
 {
     uint64_t result;
@@ -591,7 +596,7 @@ static char * const subopt_token[] = {[MAX_FLOWS_PER_THREAD] = "max-flows-per-th
                                       NULL};
 
 static void sighandler(int signum);
-static int processing_threads_error_or_eof(void);
+static WARN_UNUSED int processing_threads_error_or_eof(void);
 static void free_workflow(struct nDPId_workflow ** const workflow);
 static void serialize_and_send(struct nDPId_reader_thread * const reader_thread);
 static void jsonize_flow_event(struct nDPId_reader_thread * const reader_thread,
@@ -4622,7 +4627,7 @@ static void * processing_thread(void * const ndpi_thread_arg)
     return NULL;
 }
 
-static int processing_threads_error_or_eof(void)
+static WARN_UNUSED int processing_threads_error_or_eof(void)
 {
     for (unsigned long long int i = 0; i < nDPId_options.reader_thread_count; ++i)
     {

nio.h

@@ -3,6 +3,8 @@
 
 #include <poll.h>
 
+#define WARN_UNUSED __attribute__((__warn_unused_result__))
+
 enum
 {
     NIO_SUCCESS = 0,
@@ -34,41 +36,55 @@ struct nio
 
 void nio_init(struct nio * io);
 
+WARN_UNUSED
 int nio_use_poll(struct nio * io, nfds_t max_fds);
 
+WARN_UNUSED
 int nio_use_epoll(struct nio * io, int max_events);
 
+WARN_UNUSED
 int nio_add_fd(struct nio * io, int fd, int event_flags, void * ptr);
 
+WARN_UNUSED
 int nio_mod_fd(struct nio * io, int fd, int event_flags, void * ptr);
 
+WARN_UNUSED
 int nio_del_fd(struct nio * io, int fd);
 
+WARN_UNUSED
 int nio_run(struct nio * io, int timeout);
 
+WARN_UNUSED
 static inline int nio_get_nready(struct nio const * const io)
 {
     return io->nready;
 }
 
+WARN_UNUSED
 int nio_check(struct nio * io, int index, int events);
 
+WARN_UNUSED
 int nio_is_valid(struct nio const * const io, int index);
 
+WARN_UNUSED
 int nio_get_fd(struct nio * io, int index);
 
+WARN_UNUSED
 void * nio_get_ptr(struct nio * io, int index);
 
+WARN_UNUSED
 static inline int nio_has_input(struct nio * io, int index)
 {
     return nio_check(io, index, NIO_EVENT_INPUT);
 }
 
+WARN_UNUSED
 static inline int nio_can_output(struct nio * io, int index)
 {
     return nio_check(io, index, NIO_EVENT_OUTPUT);
 }
 
+WARN_UNUSED
 static inline int nio_has_error(struct nio * io, int index)
 {
     return nio_check(io, index, NIO_EVENT_ERROR);

utils.h

@@ -3,6 +3,8 @@
 
 #include <stdarg.h>
 
+#define WARN_UNUSED __attribute__((__warn_unused_result__))
+
 #define CMDARG(_default_value)                                                                                         \
     {                                                                                                                  \
         .value = NULL, .default_value = (_default_value)                                                               \
@@ -16,20 +18,26 @@ struct cmdarg
 
 void set_cmdarg(struct cmdarg * const ca, char const * const val);
 
+WARN_UNUSED
 char const * get_cmdarg(struct cmdarg const * const ca);
 
+WARN_UNUSED
 int is_cmdarg_set(struct cmdarg const * const ca);
 
+WARN_UNUSED
 int is_path_absolute(char const * const prefix, char const * const path);
 
 void daemonize_enable(void);
 
+WARN_UNUSED
 int is_daemonize_enabled(void);
 
+WARN_UNUSED
 int daemonize_with_pidfile(char const * const pidfile);
 
 int daemonize_shutdown(char const * const pidfile);
 
+WARN_UNUSED
 int change_user_group(char const * const user,
                       char const * const group,
                       char const * const pidfile,
@@ -42,12 +50,15 @@ void log_app_info(void);
 
 void shutdown_logging(void);
 
+WARN_UNUSED
 int enable_file_logger(char const * const log_file);
 
+WARN_UNUSED
 int get_log_file_fd(void);
 
 void enable_console_logger(void);
 
+WARN_UNUSED
 int is_console_logger_enabled(void);
 
 void vlogger(int is_error, char const * const format, va_list ap);
@@ -56,8 +67,10 @@ __attribute__((format(printf, 2, 3))) void logger(int is_error, char const * con
 
 __attribute__((format(printf, 2, 3))) void logger_early(int is_error, char const * const format, ...);
 
+WARN_UNUSED
 int set_fd_cloexec(int fd);
 
+WARN_UNUSED
 char const * get_nDPId_version(void);
 
 #endif