diff --git a/devices/center_of_mass.c b/devices/center_of_mass.c
index 1db063c..4a8561f 100644
--- a/devices/center_of_mass.c
+++ b/devices/center_of_mass.c
@@ -80,17 +80,17 @@ int center_of_mass_init(struct aylp_device *self)
 			// keys starting with _ are comments
 		} else if (!strcmp(key, "region_height")) {
 			data->region_height = json_object_get_uint64(val);
-			log_trace("region_height = %llu", data->region_height);
+			log_trace("region_height = %zu", data->region_height);
 		} else if (!strcmp(key, "region_width")) {
 			data->region_width = json_object_get_uint64(val);
-			log_trace("region_width = %llu", data->region_width);
+			log_trace("region_width = %zu", data->region_width);
 		} else if (!strcmp(key, "thread_count")) {
 			data->thread_count = json_object_get_uint64(val);
 			if (data->thread_count == 0) {
 				log_error("Correcting 0 threads to 1 thread");
 				data->thread_count = 1;
 			}
-			log_trace("thread_count = %llu", data->thread_count);
+			log_trace("thread_count = %zu", data->thread_count);
 		} else {
 			log_warn("Unknown parameter \"%s\"", key);
 		}
@@ -116,7 +116,7 @@ int center_of_mass_init(struct aylp_device *self)
 				return -1;
 			}
 		}
-		log_info("Started %llu threads", data->thread_count);
+		log_info("Started %zu threads", data->thread_count);
 		self->process = &center_of_mass_process_threaded;
 		self->close = &center_of_mass_close_threaded;
 	} else {
@@ -144,7 +144,7 @@ int center_of_mass_process(struct aylp_device *self, struct aylp_state *state)
 	size_t subap_count = y_subap_count * x_subap_count;
 	if (UNLIKELY(!subap_count)) {
 		log_error("Refusing to process zero subapertures; "
-			"region size is %llu by %llu but image is %llu by %llu",
+			"region size is %zu by %zu but image is %zu by %zu",
 			data->region_height, data->region_width, max_y, max_x
 		);
 		return -1;
@@ -216,7 +216,7 @@ int center_of_mass_process_threaded(
 	size_t n_tasks = y_subap_count * x_subap_count;
 	if (!n_tasks) {
 		log_error("Refusing to process zero subapertures; "
-			"region size is %llu by %llu but image is %llu by %llu",
+			"region size is %zu by %zu but image is %zu by %zu",
 			data->region_height, data->region_width, max_y, max_x
 		);
 		return -1;
diff --git a/devices/delay.c b/devices/delay.c
index dcdb28c..7561a91 100644
--- a/devices/delay.c
+++ b/devices/delay.c
@@ -22,10 +22,10 @@ int delay_init(struct aylp_device *self)
 			// keys starting with _ are comments
 		} else if (!strcmp(key, "s")) {
 			ts->tv_sec = (time_t)json_object_get_uint64(val);
-			log_trace("s = %u", ts->tv_sec);
+			log_trace("s = %lu", ts->tv_sec);
 		} else if (!strcmp(key, "ns")) {
 			ts->tv_nsec = (long)json_object_get_int64(val);
-			log_trace("ns = %u", ts->tv_nsec);
+			log_trace("ns = %lu", ts->tv_nsec);
 		} else {
 			log_warn("Unknown parameter \"%s\"", key);
 		}
diff --git a/devices/file_sink.c b/devices/file_sink.c
index 6b38f1c..2b4aa7b 100644
--- a/devices/file_sink.c
+++ b/devices/file_sink.c
@@ -62,7 +62,7 @@ int file_sink_process(struct aylp_device *self, struct aylp_state *state)
 	n += fwrite(data->bytes.data, 1, data->bytes.size, data->fp);
 	size_t n_expect = sizeof(struct aylp_header) + data->bytes.size;
 	if (n < n_expect) {
-		log_error("Short write: %d of %d", n, n_expect);
+		log_error("Short write: %zu of %zu", n, n_expect);
 		return -1;
 	}
 	if (needs_free) {
diff --git a/devices/logger.c b/devices/logger.c
index 1504997..9bbb39d 100644
--- a/devices/logger.c
+++ b/devices/logger.c
@@ -23,24 +23,24 @@ int logger_process(struct aylp_device *self, struct aylp_state *state)
 	UNUSED(self);
 	switch (state->header.type) {
 	case AYLP_T_VECTOR:
-		log_info("Seeing vector of size %llu:", state->vector->size);
+		log_info("Seeing vector of size %zu:", state->vector->size);
 		logn_info("");
 		pretty_vector(state->vector);
 		break;
 	case AYLP_T_MATRIX:
-		log_info("Seeing matrix of size %llux%llu:",
+		log_info("Seeing matrix of size %zux%zu:",
 			state->matrix->size1, state->matrix->size2
 		);
 		pretty_matrix(state->matrix);
 		break;
 	case AYLP_T_MATRIX_UCHAR:
-		log_info("Seeing matrix of size %llux%llu:",
+		log_info("Seeing matrix of size %zux%zu:",
 			state->matrix_uchar->size1, state->matrix_uchar->size2
 		);
 		pretty_matrix_uchar(state->matrix_uchar);
 		break;
 	default:
-		log_warn("Seeing type %hX but don't know how to print it",
+		log_warn("Seeing type %hhX but don't know how to print it",
 			state->header.type
 		);
 		if (!state->header.type)
diff --git a/devices/pid.c b/devices/pid.c
index 7698e7a..03f6996 100644
--- a/devices/pid.c
+++ b/devices/pid.c
@@ -35,7 +35,7 @@ int pid_init(struct aylp_device *self)
 			else if (!strcmp(s, "matrix"))
 				data->type = AYLP_T_MATRIX;
 			else log_error("Unrecognized type: %s", s);
-			log_trace("type = %s (0x%X)", s, data->type);
+			log_trace("type = %s (0x%hhX)", s, data->type);
 		} else if (!strcmp(key, "p")) {
 			data->p = json_object_get_double(val);
 			log_trace("p = %G", data->p);
diff --git a/devices/test_source.c b/devices/test_source.c
index 04e4e15..9a2911e 100644
--- a/devices/test_source.c
+++ b/devices/test_source.c
@@ -38,29 +38,29 @@ int test_source_init(struct aylp_device *self)
 			else if (!strcmp(s, "matrix_uchar"))
 				data->type = AYLP_T_MATRIX_UCHAR;
 			else log_error("Unrecognized type: %s", s);
-			log_trace("type = %s (0x%X)", s, data->type);
+			log_trace("type = %s (0x%hhX)", s, data->type);
 		} else if (!strcmp(key, "kind")) {
 			const char *s = json_object_get_string(val);
 			// TODO: add KIND_NOISE?
 			if (!strcmp(s, "constant")) data->kind = KIND_CONSTANT;
 			else if (!strcmp(s, "sine")) data->kind = KIND_SINE;
 			else log_error("Unrecognized kind: %s", s);
-			log_trace("kind = %s (0x%X)", s, data->kind);
+			log_trace("kind = %s (0x%hhX)", s, data->kind);
 		} else if (!strcmp(key, "size1")) {
 			data->size1 = json_object_get_uint64(val);
-			log_trace("size1 = %llu", data->size1);
+			log_trace("size1 = %zu", data->size1);
 		} else if (!strcmp(key, "size2")) {
 			data->size2 = json_object_get_uint64(val);
-			log_trace("size2 = %llu", data->size2);
+			log_trace("size2 = %zu", data->size2);
 		} else if (!strcmp(key, "frequency")) {
 			data->frequency = json_object_get_double(val);
-			log_trace("frequency = %E", data->frequency);
+			log_trace("frequency = %G", data->frequency);
 		} else if (!strcmp(key, "amplitude")) {
 			data->amplitude = json_object_get_double(val);
-			log_trace("amplitude = %E", data->amplitude);
+			log_trace("amplitude = %G", data->amplitude);
 		} else if (!strcmp(key, "offset")) {
 			data->offset = json_object_get_double(val);
-			log_trace("offset = %E", data->offset);
+			log_trace("offset = %G", data->offset);
 		} else {
 			log_warn("Unknown parameter \"%s\"", key);
 		}
diff --git a/devices/udp_sink.c b/devices/udp_sink.c
index b91517e..382401f 100644
--- a/devices/udp_sink.c
+++ b/devices/udp_sink.c
@@ -92,7 +92,7 @@ int udp_sink_process(struct aylp_device *self, struct aylp_state *state)
 	data->iovecs[1].iov_len = data->bytes.size;
 	// write all the data in one go
 	size_t n = data->iovecs[0].iov_len + data->iovecs[1].iov_len;
-	log_trace("Writing %llu bytes to UDP", n);
+	log_trace("Writing %zu bytes to UDP", n);
 	ssize_t err = writev(data->sock, data->iovecs, 2);
 	if (err < 0) {
 		// if n > SSIZE_MAX, this will fire, so we don't need to check
@@ -102,7 +102,7 @@ int udp_sink_process(struct aylp_device *self, struct aylp_state *state)
 		if (err == -1) {
 			log_error("Couldn't send data: %s", strerror(errno));
 		} else {
-			log_error("Short write: %d of %d", err, n);
+			log_error("Short write: %zu of %zu", err, n);
 		}
 	}
 	if (needs_free) {
diff --git a/devices/vonkarman_stream.c b/devices/vonkarman_stream.c
index 7405cbc..a91fec2 100644
--- a/devices/vonkarman_stream.c
+++ b/devices/vonkarman_stream.c
@@ -72,7 +72,7 @@ static int generate_phase_screen(struct aylp_device *self)
 	// by the spectrum as we go.
 	size_t M = data->phase_screen->size1;
 	size_t N = data->phase_screen->size2;
-	log_trace("Allocated %u by %u matrix for phase screen", M, N);
+	log_trace("Allocated %zu by %zu matrix for phase screen", M, N);
 	for (size_t x=0; x<M; x++) {
 		for (size_t y=0; y<N; y++) {
 			// von Kármán spectrum amplitude
@@ -188,25 +188,25 @@ int vonkarman_stream_init(struct aylp_device *self)
 			log_trace("pitch = %G", data->pitch);
 		} else if (!strcmp(key, "screen_size")) {
 			data->screen_size = json_object_get_uint64(val);
-			log_trace("screen_size = %u", data->screen_size);
+			log_trace("screen_size = %zu", data->screen_size);
 		} else if (!strcmp(key, "win_height")) {
 			data->win_height = json_object_get_uint64(val);
-			log_trace("win_height = %u", data->win_height);
+			log_trace("win_height = %zu", data->win_height);
 		} else if (!strcmp(key, "win_width")) {
 			data->win_width = json_object_get_uint64(val);
-			log_trace("win_width = %u", data->win_width);
+			log_trace("win_width = %zu", data->win_width);
 		} else if (!strcmp(key, "start_y")) {
 			data->cur_y = json_object_get_uint64(val);
-			log_trace("start_y = %u", data->cur_y);
+			log_trace("start_y = %zu", data->cur_y);
 		} else if (!strcmp(key, "start_x")) {
 			data->cur_x = json_object_get_uint64(val);
-			log_trace("start_x = %u", data->cur_x);
+			log_trace("start_x = %zu", data->cur_x);
 		} else if (!strcmp(key, "step_y")) {
 			data->cur_step_y = json_object_get_int(val);
-			log_trace("step_y = %u", data->cur_step_y);
+			log_trace("step_y = %d", data->cur_step_y);
 		} else if (!strcmp(key, "step_x")) {
 			data->cur_step_x = json_object_get_int(val);
-			log_trace("step_x = %u", data->cur_step_x);
+			log_trace("step_x = %d", data->cur_step_x);
 		} else {
 			log_warn("Unknown parameter \"%s\"", key);
 		}
@@ -306,7 +306,7 @@ int vonkarman_stream_process(struct aylp_device *self, struct aylp_state *state)
 	}
 	data->cur_y += data->cur_step_y;
 	data->cur_x += data->cur_step_x;
-	log_trace("Window at y,x indices %lu,%lu", data->cur_y, data->cur_x);
+	log_trace("Window at y,x indices %zu,%zu", data->cur_y, data->cur_x);
 	data->sub_view = gsl_matrix_submatrix(
 		data->phase_screen,
 		data->cur_y, data->cur_x,
diff --git a/libaylp/block.c b/libaylp/block.c
index 1526c2f..98d7ed7 100644
--- a/libaylp/block.c
+++ b/libaylp/block.c
@@ -22,14 +22,14 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 	case AYLP_T_BLOCK: {
 		bytes->size = sizeof(double) * state->block->size;
 		bytes->data = (unsigned char *)state->block->data;
-		log_trace("got block of %llu doubles", state->block->size);
+		log_trace("got block of %zu doubles", state->block->size);
 		return 0;
 	}
 	case AYLP_T_VECTOR: {
 		gsl_vector *v = state->vector;
 		bytes->size = sizeof(double) * v->size;
 		if (LIKELY(v->stride == 1)) {
-			log_trace("got contiguous vector of %llu doubles",
+			log_trace("got contiguous vector of %zu doubles",
 				state->vector->size
 			);
 			bytes->data = (unsigned char *)v->data;
@@ -41,7 +41,7 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 					v->data[i * v->stride]
 				;
 			}
-			log_trace("got non-contiguous vector of %llu doubles",
+			log_trace("got non-contiguous vector of %zu doubles",
 				state->vector->size
 			);
 			return 1;
@@ -53,7 +53,7 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 		if (LIKELY(m->tda == m->size2)) {
 			// rows are contiguous
 			bytes->data = (unsigned char *)m->data;
-			log_trace("got contiguous matrix of %llu by %llu "
+			log_trace("got contiguous matrix of %zu by %zu "
 				"doubles",
 				state->matrix->size1, state->matrix->size2
 			);
@@ -61,7 +61,7 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 		} else {
 			// rows are not contiguous
 			bytes->data = xmalloc(bytes->size);
-			log_trace("got non-contiguous matrix of %llu by %llu "
+			log_trace("got non-contiguous matrix of %zu by %zu "
 				"doubles",
 				state->matrix->size1, state->matrix->size2
 			);
@@ -77,7 +77,7 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 	case AYLP_T_BLOCK_UCHAR: {
 		bytes->size = state->block_uchar->size;
 		bytes->data = state->block_uchar->data;
-		log_trace("got block of %llu uchars", bytes->size);
+		log_trace("got block of %zu uchars", bytes->size);
 		return 0;
 	}
 	case AYLP_T_MATRIX_UCHAR: {
@@ -86,14 +86,14 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 		if (LIKELY(m->tda == m->size2)) {
 			// rows are contiguous
 			bytes->data = m->data;
-			log_trace("got contiguous matrix of %llu uchars",
+			log_trace("got contiguous matrix of %zu uchars",
 				bytes->size
 			);
 			return 0;
 		} else {
 			// rows are not contiguous
 			bytes->data = xmalloc(bytes->size);
-			log_trace("got non-contiguous matrix of %llu uchars",
+			log_trace("got non-contiguous matrix of %zu uchars",
 				bytes->size
 			);
 			for (size_t i = 0; i < m->size1; i++) {
@@ -106,7 +106,7 @@ int get_contiguous_bytes(gsl_block_uchar *bytes, struct aylp_state *state)
 		}
 	}
 	default: {
-		log_fatal("Bug: unsupported type 0x%hX", state->header.type);
+		log_fatal("Bug: unsupported type 0x%hhX", state->header.type);
 		exit(EXIT_FAILURE);
 		return -1;
 	}