fix: replace usleep with nanosleep and fix const correctness

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>

src/looper.c

@@ -1,24 +1,24 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <jack/jack.h>
-#include <jack/midiport.h>
-#include <stdatomic.h>
-#include <math.h>
 #include "looper.h"
 #include "channel.h"
 #include "midi.h"
+#include <jack/jack.h>
+#include <jack/midiport.h>
+#include <math.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
 /* Global state (shared across files) */
 struct channel_t channels[MAX_CHANNELS];
-atomic_int  channel_count = 0;
-int         next_channel_id = 1;
-atomic_int  cmd_add = 0;
-atomic_int  cmd_remove = 0;
+atomic_int channel_count = 0;
+int next_channel_id = 1;
+atomic_int cmd_add = 0;
+atomic_int cmd_remove = 0;
 jack_port_t *midi_control_port = NULL;
 jack_port_t *midi_clock_port = NULL;
-atomic_int  control_key_active = 0;
-atomic_int  bind_channel = 0;
+atomic_int control_key_active = 0;
+atomic_int bind_channel = 0;
 
 /* Deferred removal index (1 second grace) */
 static int pending_unregister_idx = -1;
@@ -26,211 +26,215 @@ static int pending_unregister_idx = -1;
 /* ----------------------------------------------------------------
  * process callback
  * ---------------------------------------------------------------- */
-int process_callback(jack_nframes_t nframes, void *arg)
-{
-    (void)arg;
+int process_callback(jack_nframes_t nframes, void *arg) {
+  (void)arg;
 
-    if (midi_control_port) {
-        void *midi_ctrl_buf = jack_port_get_buffer(midi_control_port, nframes);
-        if (midi_ctrl_buf) {
-            midi_handle_events(midi_ctrl_buf, nframes);
-        }
+  if (midi_control_port) {
+    void *midi_ctrl_buf = jack_port_get_buffer(midi_control_port, nframes);
+    if (midi_ctrl_buf) {
+      midi_handle_events(midi_ctrl_buf, nframes);
+    }
+  }
+
+  /* process each active channel */
+  for (int c = 0; c < MAX_CHANNELS; c++) {
+    if (!atomic_load(&channels[c].active))
+      continue;
+
+    /* Guard against NULL ports (e.g. if port registration failed) */
+    if (!channels[c].audio_in || !channels[c].audio_out) {
+      fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n", c);
+      continue;
     }
 
-    /* process each active channel */
-    for (int c = 0; c < MAX_CHANNELS; c++) {
-        if (!atomic_load(&channels[c].active)) continue;
+    const jack_default_audio_sample_t *in =
+        (const jack_default_audio_sample_t *)jack_port_get_buffer(
+            channels[c].audio_in, nframes);
+    jack_default_audio_sample_t *out =
+        (jack_default_audio_sample_t *)jack_port_get_buffer(
+            channels[c].audio_out, nframes);
+    if (!out)
+      continue;
 
-        /* Guard against NULL ports (e.g. if port registration failed) */
-        if (!channels[c].audio_in || !channels[c].audio_out) {
-            fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n", c);
-            continue;
-        }
+    int state = atomic_load(&channels[c].state);
 
-        jack_default_audio_sample_t *in  = (jack_default_audio_sample_t *)
-            jack_port_get_buffer(channels[c].audio_in, nframes);
-        jack_default_audio_sample_t *out = (jack_default_audio_sample_t *)
-            jack_port_get_buffer(channels[c].audio_out, nframes);
-        if (!out) continue;
-
-        int state = atomic_load(&channels[c].state);
-
-        if (state != channels[c].prev_state) {
-            switch (state) {
-            case STATE_RECORD:
-                channels[c].record_pos = 0;
-                channels[c].loop_count = 0;
-                break;
-            case STATE_LOOPING:
-                if (channels[c].record_pos > 0)
-                    channels[c].loop_count = channels[c].record_pos;
-                channels[c].playback_pos = 0;
-                break;
-            default:
-                break;
-            }
-        }
-
-        jack_nframes_t i;
-        switch (state) {
-        case STATE_RECORD:
-            if (in) {
-                for (i = 0; i < nframes; i++) {
-                    if (channels[c].record_pos < LOOP_BUF_SIZE)
-                        channels[c].loop_buffer[channels[c].record_pos++] = ((const float *)in)[i];
-                    ((float *)out)[i] = ((const float *)in)[i];
-                }
-            } else {
-                memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
-            }
-            break;
-
-        case STATE_LOOPING:
-            if (channels[c].loop_count > 0) {
-                float *outf = (float *)out;
-                for (i = 0; i < nframes; i++) {
-                    outf[i] = channels[c].loop_buffer[channels[c].playback_pos];
-                    channels[c].playback_pos = (channels[c].playback_pos + 1) % channels[c].loop_count;
-                }
-            } else {
-                memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
-            }
-            break;
-
-        case STATE_PAUSED:
-            memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
-            break;
-
-        default: /* IDLE */
-            if (in) {
-                memcpy(out, in, sizeof(jack_default_audio_sample_t) * nframes);
-            } else {
-                memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
-            }
-            break;
-        }
-
-        channels[c].prev_state = state;
+    if (state != channels[c].prev_state) {
+      switch (state) {
+      case STATE_RECORD:
+        channels[c].record_pos = 0;
+        channels[c].loop_count = 0;
+        break;
+      case STATE_LOOPING:
+        if (channels[c].record_pos > 0)
+          channels[c].loop_count = channels[c].record_pos;
+        channels[c].playback_pos = 0;
+        break;
+      default:
+        break;
+      }
     }
 
-    /* MIDI clock events – affect channel 0 only */
-    if (midi_clock_port) {
-        void *midi_clock_buf = jack_port_get_buffer(midi_clock_port, nframes);
-        if (midi_clock_buf) {
-            jack_nframes_t n_clock_events = jack_midi_get_event_count(midi_clock_buf);
-            jack_midi_event_t cev;
-            for (jack_nframes_t j = 0; j < n_clock_events; j++) {
-                if (jack_midi_event_get(&cev, midi_clock_buf, j) != 0) continue;
-                if (cev.size >= 1) {
-                    unsigned char msg = cev.buffer[0];
-                    switch (msg) {
-                    case 0xFA: {
-                        int s = atomic_load(&channels[0].state);
-                        if (s == STATE_IDLE) atomic_store(&channels[0].state, STATE_RECORD);
-                        break;
-                    }
-                    case 0xFC:
-                        atomic_store(&channels[0].state, STATE_IDLE);
-                        break;
-                    case 0xFB: {
-                        int s = atomic_load(&channels[0].state);
-                        if (s == STATE_PAUSED) atomic_store(&channels[0].state, STATE_LOOPING);
-                        break;
-                    }
-                    default:
-                        break;
-                    }
-                }
-            }
+    jack_nframes_t i;
+    switch (state) {
+    case STATE_RECORD:
+      if (in) {
+        for (i = 0; i < nframes; i++) {
+          if (channels[c].record_pos < LOOP_BUF_SIZE)
+            channels[c].loop_buffer[channels[c].record_pos++] =
+                ((const float *)in)[i];
+          // cppcheck-suppress unreadVariable
+          ((float *)out)[i] = ((const float *)in)[i];
         }
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
+
+    case STATE_LOOPING:
+      if (channels[c].loop_count > 0) {
+        float *outf = (float *)out;
+        for (i = 0; i < nframes; i++) {
+          outf[i] = channels[c].loop_buffer[channels[c].playback_pos];
+          channels[c].playback_pos =
+              (channels[c].playback_pos + 1) % channels[c].loop_count;
+        }
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
+
+    case STATE_PAUSED:
+      memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      break;
+
+    default: /* IDLE */
+      if (in) {
+        memcpy(out, in, sizeof(jack_default_audio_sample_t) * nframes);
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
     }
 
-    return 0;
+    channels[c].prev_state = state;
+  }
+
+  /* MIDI clock events – affect channel 0 only */
+  if (midi_clock_port) {
+    void *midi_clock_buf = jack_port_get_buffer(midi_clock_port, nframes);
+    if (midi_clock_buf) {
+      jack_nframes_t n_clock_events = jack_midi_get_event_count(midi_clock_buf);
+      jack_midi_event_t cev;
+      for (jack_nframes_t j = 0; j < n_clock_events; j++) {
+        if (jack_midi_event_get(&cev, midi_clock_buf, j) != 0)
+          continue;
+        if (cev.size >= 1) {
+          unsigned char msg = cev.buffer[0];
+          switch (msg) {
+          case 0xFA: {
+            int s = atomic_load(&channels[0].state);
+            if (s == STATE_IDLE)
+              atomic_store(&channels[0].state, STATE_RECORD);
+            break;
+          }
+          case 0xFC:
+            atomic_store(&channels[0].state, STATE_IDLE);
+            break;
+          case 0xFB: {
+            int s = atomic_load(&channels[0].state);
+            if (s == STATE_PAUSED)
+              atomic_store(&channels[0].state, STATE_LOOPING);
+            break;
+          }
+          default:
+            break;
+          }
+        }
+      }
+    }
+  }
+
+  return 0;
 }
 
 /* ----------------------------------------------------------------
  * shutdown callback
  * ---------------------------------------------------------------- */
-void jack_shutdown_cb(void *arg)
-{
-    (void)arg;
-    fprintf(stderr, "JACK shutdown\n");
-    exit(0);
+void jack_shutdown_cb(void *arg) {
+  (void)arg;
+  fprintf(stderr, "JACK shutdown\n");
+  exit(0);
 }
 
 /* ----------------------------------------------------------------
  * looper initialisation
  * ---------------------------------------------------------------- */
-int looper_init(jack_client_t *client)
-{
-    /* channel 0 */
-    channels[0].active = 1;
-    atomic_store(&channels[0].state, STATE_IDLE);
-    channels[0].prev_state = -1;
-    channels[0].loop_count = 0;
-    channels[0].record_pos = 0;
-    channels[0].playback_pos = 0;
+int looper_init(jack_client_t *client) {
+  /* channel 0 */
+  channels[0].active = 1;
+  atomic_store(&channels[0].state, STATE_IDLE);
+  channels[0].prev_state = -1;
+  channels[0].loop_count = 0;
+  channels[0].record_pos = 0;
+  channels[0].playback_pos = 0;
 
-    channels[0].audio_in = jack_port_register(client, "input",
-                                               JACK_DEFAULT_AUDIO_TYPE,
-                                               JackPortIsInput, 0);
-    channels[0].audio_out = jack_port_register(client, "output",
-                                                JACK_DEFAULT_AUDIO_TYPE,
-                                                JackPortIsOutput, 0);
-    if (!channels[0].audio_in || !channels[0].audio_out) {
-        fprintf(stderr, "Could not create audio ports for channel 0\n");
-        return -1;
-    }
-    channel_count = 1;
+  channels[0].audio_in = jack_port_register(
+      client, "input", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
+  channels[0].audio_out = jack_port_register(
+      client, "output", JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0);
+  if (!channels[0].audio_in || !channels[0].audio_out) {
+    fprintf(stderr, "Could not create audio ports for channel 0\n");
+    return -1;
+  }
+  channel_count = 1;
 
-    midi_control_port = jack_port_register(client, "control",
-                                            JACK_DEFAULT_MIDI_TYPE,
-                                            JackPortIsInput, 0);
-    midi_clock_port   = jack_port_register(client, "clock",
-                                            JACK_DEFAULT_MIDI_TYPE,
-                                            JackPortIsInput, 0);
-    if (!midi_control_port || !midi_clock_port) {
-        fprintf(stderr, "Could not create MIDI ports\n");
-        return -1;
-    }
+  midi_control_port = jack_port_register(
+      client, "control", JACK_DEFAULT_MIDI_TYPE, JackPortIsInput, 0);
+  midi_clock_port = jack_port_register(client, "clock", JACK_DEFAULT_MIDI_TYPE,
+                                       JackPortIsInput, 0);
+  if (!midi_control_port || !midi_clock_port) {
+    fprintf(stderr, "Could not create MIDI ports\n");
+    return -1;
+  }
 
-    return 0;
+  return 0;
 }
 
 /* ----------------------------------------------------------------
  * main‑loop command processing
  * ---------------------------------------------------------------- */
-void looper_process_commands(jack_client_t *client)
-{
-    /* Unregister any ports that were marked for deferred removal.
-       By now the real‑time thread has had at least one full cycle
-       to see the `active = 0` store. */
-    if (pending_unregister_idx != -1) {
-        int idx = pending_unregister_idx;
-        if (channels[idx].audio_in)
-            jack_port_unregister(client, channels[idx].audio_in);
-        if (channels[idx].audio_out)
-            jack_port_unregister(client, channels[idx].audio_out);
-        pending_unregister_idx = -1;
-    }
+void looper_process_commands(jack_client_t *client) {
+  /* Unregister any ports that were marked for deferred removal.
+     By now the real‑time thread has had at least one full cycle
+     to see the `active = 0` store. */
+  if (pending_unregister_idx != -1) {
+    int idx = pending_unregister_idx;
+    if (channels[idx].audio_in)
+      jack_port_unregister(client, channels[idx].audio_in);
+    if (channels[idx].audio_out)
+      jack_port_unregister(client, channels[idx].audio_out);
+    pending_unregister_idx = -1;
+  }
 
-    if (atomic_exchange(&cmd_add, 0)) {
-        int idx;
-        for (idx = 0; idx < MAX_CHANNELS; idx++)
-            if (!channels[idx].active) break;
-        if (idx < MAX_CHANNELS) {
-            channel_add(client, idx);
-        }
+  if (atomic_exchange(&cmd_add, 0)) {
+    int idx;
+    for (idx = 0; idx < MAX_CHANNELS; idx++)
+      if (!channels[idx].active)
+        break;
+    if (idx < MAX_CHANNELS) {
+      channel_add(client, idx);
     }
+  }
 
-    if (atomic_exchange(&cmd_remove, 0)) {
-        int remove_idx = -1;
-        for (int idx = 1; idx < MAX_CHANNELS; idx++)
-            if (channels[idx].active) remove_idx = idx;
-        if (remove_idx != -1) {
-            /* Mark inactive now; ports will be unregistered next round */
-            channel_remove(client, remove_idx);
-            pending_unregister_idx = remove_idx;
-        }
+  if (atomic_exchange(&cmd_remove, 0)) {
+    int remove_idx = -1;
+    for (int idx = 1; idx < MAX_CHANNELS; idx++)
+      if (channels[idx].active)
+        remove_idx = idx;
+    if (remove_idx != -1) {
+      /* Mark inactive now; ports will be unregistered next round */
+      channel_remove(client, remove_idx);
+      pending_unregister_idx = remove_idx;
     }
+  }
 }

src/main.c

@@ -1,50 +1,50 @@
+#include "looper.h"
+#include <jack/jack.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <jack/jack.h>
-#include "looper.h"
+#include <time.h>
 
-int main(int argc, char *argv[])
-{
-    (void)argc;
-    (void)argv;
-    const char *client_name = "looper";
-    jack_options_t options = JackNullOption;
-    jack_status_t status;
+int main(int argc, char *argv[]) {
+  (void)argc;
+  (void)argv;
+  const char *client_name = "looper";
+  jack_options_t options = JackNullOption;
+  jack_status_t status;
 
-    jack_client_t *client = jack_client_open(client_name, options, &status);
-    if (client == NULL) {
-        fprintf(stderr, "jack_client_open() failed, status = 0x%2.0x\n", status);
-        if (status & JackServerFailed)
-            fprintf(stderr, "Unable to connect to JACK server\n");
-        return 1;
-    }
+  jack_client_t *client = jack_client_open(client_name, options, &status);
+  if (client == NULL) {
+    fprintf(stderr, "jack_client_open() failed, status = 0x%2.0x\n", status);
+    if (status & JackServerFailed)
+      fprintf(stderr, "Unable to connect to JACK server\n");
+    return 1;
+  }
 
-    if (status & JackNameNotUnique)
-        client_name = jack_get_client_name(client);
+  if (status & JackNameNotUnique)
+    client_name = jack_get_client_name(client);
 
-    jack_set_process_callback(client, process_callback, NULL);
-    jack_on_shutdown(client, jack_shutdown_cb, NULL);
-
-    if (looper_init(client) != 0) {
-        fprintf(stderr, "looper initialisation failed\n");
-        jack_client_close(client);
-        return 1;
-    }
-
-    if (jack_activate(client)) {
-        fprintf(stderr, "Cannot activate client\n");
-        jack_client_close(client);
-        return 1;
-    }
-
-    fprintf(stderr, "looper running (client name '%s')\n", client_name);
-
-    while (1) {
-        looper_process_commands(client);
-        usleep(50000);   /* check commands every 50 ms */
-    }
+  jack_set_process_callback(client, process_callback, NULL);
+  jack_on_shutdown(client, jack_shutdown_cb, NULL);
 
+  if (looper_init(client) != 0) {
+    fprintf(stderr, "looper initialisation failed\n");
     jack_client_close(client);
-    return 0;
+    return 1;
+  }
+
+  if (jack_activate(client)) {
+    fprintf(stderr, "Cannot activate client\n");
+    jack_client_close(client);
+    return 1;
+  }
+
+  fprintf(stderr, "looper running (client name '%s')\n", client_name);
+
+  while (1) {
+    looper_process_commands(client);
+    { struct timespec ts = { .tv_sec = 0, .tv_nsec = 50000000 }; nanosleep(&ts, NULL); } /* check commands every 50 ms */
+  }
+
+  jack_client_close(client);
+  return 0;
 }

tests/integration.c

@@ -10,6 +10,7 @@
 #include <jack/jack.h>
 #include <jack/midiport.h>
 #include <math.h>
+#include <time.h>
 
 /* static variables for passthrough test */
 static jack_port_t *passthrough_output_port = NULL;
@@ -32,6 +33,13 @@ static jack_client_t *midi_inject_client = NULL;
 static unsigned char midi_inject_note = 0;
 static unsigned char midi_inject_velocity = 0;
 
+static void safe_usleep(unsigned int usec) {
+    struct timespec ts;
+    ts.tv_sec = usec / 1000000;
+    ts.tv_nsec = (usec % 1000000) * 1000L;
+    nanosleep(&ts, NULL);
+}
+
 static int midi_inject_process(jack_nframes_t nframes, void *arg) {
     (void)arg;
     if (!midi_inject_port) return 0;
@@ -57,8 +65,8 @@ static int passthrough_process(jack_nframes_t nframes, void *arg) {
     (void)arg;
     jack_default_audio_sample_t *out =
         (jack_default_audio_sample_t *)jack_port_get_buffer(passthrough_output_port, nframes);
-    jack_default_audio_sample_t *in =
-        (jack_default_audio_sample_t *)jack_port_get_buffer(passthrough_input_port, nframes);
+    const jack_default_audio_sample_t *in =
+        (const jack_default_audio_sample_t *)jack_port_get_buffer(passthrough_input_port, nframes);
     if (!out || !in) return 0;
     float *outf = out;
     const float *inf = in;
@@ -195,7 +203,7 @@ static int test_audio_pass_through(void) {
         waitpid(pid, NULL, 0);
         return 1;
     }
-    usleep(2200000); /* 2.2 seconds */
+    safe_usleep(2200000);
     int saw_input = passthrough_done;
     double rms = passthrough_total_samples > 0 ?
                  sqrt(passthrough_sum_sq / passthrough_total_samples) : 0.0;
@@ -313,7 +321,7 @@ static int test_looper_looping(void) {
         kill(pid, SIGTERM); waitpid(pid, NULL, 0);
         return 1;
     }
-    usleep(500000);               /* allow state to change (500ms) */
+    safe_usleep(500000);               /* allow state to change (500ms) */
 
     int sr = jack_get_sample_rate(client);
     continuous_sine = 0;          /* disable continuous tone */
@@ -337,10 +345,10 @@ static int test_looper_looping(void) {
         return 1;
     }
 
-    usleep(150000);               /* let beep start */
+    safe_usleep(150000);               /* let beep start */
 
     /* ensure beep is fully captured */
-    usleep(800000);   /* 0.8s after start of beep */
+    safe_usleep(800000);   /* 0.8s after start of beep */
 
     if (send_jack_note_on("looper:control", 1, 127) != 0) {
         jack_client_close(client);
@@ -349,7 +357,7 @@ static int test_looper_looping(void) {
     }
 
     /* wait enough time for several loops (4 seconds to be safe) */
-    usleep(4000000);
+    safe_usleep(4000000);
 
     jack_deactivate(client);
     jack_client_close(client);
@@ -390,7 +398,7 @@ static int test_multiple_channels(void) {
     }
     /* wait long enough for the looper's main loop to process the add command
        (it sleeps for 1 second between checks, so 1.5 s is safe) */
-    usleep(1500000);
+    safe_usleep(1500000);
 
     int found = 0;
     const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
@@ -500,7 +508,7 @@ static int test_control_key_modifier(void) {
         fprintf(stderr, "  FAIL: send note 62 for loop\n");
         return 1;
     }
-    usleep(2000000);   /* wait for a few loops */
+    safe_usleep(2000000);
     jack_deactivate(client);
     jack_client_close(client);
     kill(pid, SIGTERM);
@@ -613,7 +621,7 @@ static int test_bind_channel(void) {
         fprintf(stderr, "  FAIL: toggle for loop\n");
         return 1;
     }
-    usleep(2000000);
+    safe_usleep(2000000);
     jack_deactivate(client);
     jack_client_close(client);
     kill(pid, SIGTERM);
@@ -741,7 +749,7 @@ static int test_bind_unbind(void) {
         fprintf(stderr, "  FAIL: toggle for loop\n");
         return 1;
     }
-    usleep(2000000);
+    safe_usleep(2000000);
     jack_deactivate(client);
     jack_client_close(client);
     kill(pid, SIGTERM);
@@ -776,7 +784,7 @@ static int test_remove_channel(void) {
         fprintf(stderr, "  FAIL: send note 60 failed\n");
         return 1;
     }
-    usleep(1500000);
+    safe_usleep(1500000);
     /* verify channel1_input exists */
     const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
     int found = 0;
@@ -803,7 +811,7 @@ static int test_remove_channel(void) {
         fprintf(stderr, "  FAIL: send note 61 failed\n");
         return 1;
     }
-    usleep(1500000);
+    safe_usleep(1500000);
     /* verify channel1_input has disappeared */
     ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
     int still_found = 0;