diff --git a/src/emu/clkoff.h b/src/emu/clkoff.h
index c080105..74dd3f4 100644
--- a/src/emu/clkoff.h
+++ b/src/emu/clkoff.h
@@ -4,6 +4,7 @@
 #ifndef CLKOFF_H
 #define CLKOFF_H
 
+#include "common.h"
 #include "uthash.h"
 
 #include <stdio.h>
@@ -24,9 +25,9 @@ struct clkoff {
 	struct clkoff_entry **index;
 };
 
-void clkoff_init(struct clkoff *table);
-int clkoff_load(struct clkoff *table, FILE *file);
-int clkoff_count(struct clkoff *table);
-struct clkoff_entry *clkoff_get(struct clkoff *table, int i);
+        void clkoff_init(struct clkoff *table);
+USE_RET int clkoff_load(struct clkoff *table, FILE *file);
+USE_RET int clkoff_count(struct clkoff *table);
+USE_RET struct clkoff_entry *clkoff_get(struct clkoff *table, int i);
 
 #endif /* CLKOFF_H */
diff --git a/src/emu/cpu.h b/src/emu/cpu.h
index 517c2ba..7bf5aec 100644
--- a/src/emu/cpu.h
+++ b/src/emu/cpu.h
@@ -78,7 +78,7 @@ USE_RET int cpu_add_thread(struct cpu *cpu, struct thread *thread);
 USE_RET int cpu_remove_thread(struct cpu *cpu, struct thread *thread);
 USE_RET int cpu_migrate_thread(struct cpu *cpu, struct thread *thread, struct cpu *newcpu);
 
-struct chan *cpu_get_th_chan(struct cpu *cpu, enum track_th mode);
-struct pcf_value *cpu_add_to_pcf_type(struct cpu *cpu, struct pcf_type *type);
+USE_RET struct chan *cpu_get_th_chan(struct cpu *cpu, enum track_th mode);
+USE_RET struct pcf_value *cpu_add_to_pcf_type(struct cpu *cpu, struct pcf_type *type);
 
 #endif /* CPU_H */
diff --git a/src/emu/emu.h b/src/emu/emu.h
index 7ca0193..2bf16d9 100644
--- a/src/emu/emu.h
+++ b/src/emu/emu.h
@@ -14,11 +14,6 @@
 #include "recorder.h"
 #include "emu_stat.h"
 
-enum error_values {
-	ST_BAD = 666,
-	ST_TOO_MANY_TH = 777,
-};
-
 struct emu {
 	struct bay bay;
 
@@ -40,15 +35,9 @@ struct emu {
 	struct loom *loom;
 };
 
-int emu_init(struct emu *emu, int argc, char *argv[]);
-int emu_connect(struct emu *emu);
-int emu_step(struct emu *emu);
-int emu_finish(struct emu *emu);
-
-static inline struct emu *
-emu_get(void *ptr)
-{
-	return (struct emu *) ptr;
-}
+USE_RET int emu_init(struct emu *emu, int argc, char *argv[]);
+USE_RET int emu_connect(struct emu *emu);
+USE_RET int emu_step(struct emu *emu);
+USE_RET int emu_finish(struct emu *emu);
 
 #endif /* EMU_H */
diff --git a/src/emu/extend.h b/src/emu/extend.h
index eb6333f..762c5fd 100644
--- a/src/emu/extend.h
+++ b/src/emu/extend.h
@@ -4,14 +4,16 @@
 #ifndef EXTEND_H
 #define EXTEND_H
 
+#include "common.h"
+
 #define MAX_EXTEND 256
 
 struct extend {
 	void *ctx[MAX_EXTEND];
 };
 
-void extend_set(struct extend *ext, int id, void *ctx);
-void *extend_get(struct extend *ext, int id);
+        void extend_set(struct extend *ext, int id, void *ctx);
+USE_RET void *extend_get(struct extend *ext, int id);
 
 #define EXT(st, m) extend_get(&(st)->ext, (m))
 
diff --git a/src/emu/loom.h b/src/emu/loom.h
index 8baf461..cd53f35 100644
--- a/src/emu/loom.h
+++ b/src/emu/loom.h
@@ -13,6 +13,7 @@ struct loom;
 #include "cpu.h"
 #include "proc.h"
 #include "thread.h"
+#include "common.h"
 
 struct loom {
 	size_t gindex;
@@ -47,22 +48,22 @@ struct loom {
 	struct loom *next;
 	struct loom *prev;
 
-	//struct model_ctx ctx;
+	struct extend ext;
 };
 
-int loom_matches(const char *relpath);
-int loom_init_begin(struct loom *loom, const char *name);
-int loom_init_end(struct loom *loom);
-int loom_add_cpu(struct loom *loom, struct cpu *cpu);
-int64_t loom_get_gindex(struct loom *loom);
-void loom_set_gindex(struct loom *loom, int64_t gindex);
-struct cpu *loom_find_cpu(struct loom *loom, int phyid);
-struct cpu *loom_get_cpu(struct loom *loom, int index);
-void loom_set_vcpu(struct loom *loom, struct cpu *vcpu);
-struct cpu *loom_get_vcpu(struct loom *loom);
-struct proc *loom_find_proc(struct loom *loom, pid_t pid);
-struct thread *loom_find_thread(struct loom *loom, int tid);
-int loom_add_proc(struct loom *loom, struct proc *proc);
-void loom_sort(struct loom *loom);
+USE_RET int loom_matches(const char *relpath);
+USE_RET int loom_init_begin(struct loom *loom, const char *name);
+USE_RET int loom_init_end(struct loom *loom);
+USE_RET int loom_add_cpu(struct loom *loom, struct cpu *cpu);
+USE_RET int64_t loom_get_gindex(struct loom *loom);
+        void loom_set_gindex(struct loom *loom, int64_t gindex);
+USE_RET struct cpu *loom_find_cpu(struct loom *loom, int phyid);
+USE_RET struct cpu *loom_get_cpu(struct loom *loom, int index);
+        void loom_set_vcpu(struct loom *loom, struct cpu *vcpu);
+USE_RET struct cpu *loom_get_vcpu(struct loom *loom);
+USE_RET struct proc *loom_find_proc(struct loom *loom, pid_t pid);
+USE_RET struct thread *loom_find_thread(struct loom *loom, int tid);
+USE_RET int loom_add_proc(struct loom *loom, struct proc *proc);
+        void loom_sort(struct loom *loom);
 
 #endif /* LOOM_H */
diff --git a/src/emu/metadata.h b/src/emu/metadata.h
index d3e711f..244d9bf 100644
--- a/src/emu/metadata.h
+++ b/src/emu/metadata.h
@@ -6,7 +6,8 @@
 
 #include "loom.h"
 #include "proc.h"
+#include "common.h"
 
-int metadata_load(const char *path, struct loom *loom, struct proc *proc);
+USE_RET int metadata_load(const char *path, struct loom *loom, struct proc *proc);
 
 #endif /* METADATA_H */
diff --git a/src/emu/model.h b/src/emu/model.h
index 5d59fc2..5533001 100644
--- a/src/emu/model.h
+++ b/src/emu/model.h
@@ -5,6 +5,7 @@
 #define MODEL_H
 
 #include "emu_hook.h"
+#include "common.h"
 
 struct model_spec {
 	const char *name;
@@ -25,13 +26,12 @@ struct model {
 	int enabled[MAX_MODELS];
 };
 
-void model_init(struct model *model);
-int model_register(struct model *model, struct model_spec *spec);
-
-int model_probe(struct model *model, struct emu *emu);
-int model_create(struct model *model, struct emu *emu);
-int model_connect(struct model *model, struct emu *emu);
-int model_event(struct model *model, struct emu *emu, int index);
-int model_finish(struct model *model, struct emu *emu);
+        void model_init(struct model *model);
+USE_RET int model_register(struct model *model, struct model_spec *spec);
+USE_RET int model_probe(struct model *model, struct emu *emu);
+USE_RET int model_create(struct model *model, struct emu *emu);
+USE_RET int model_connect(struct model *model, struct emu *emu);
+USE_RET int model_event(struct model *model, struct emu *emu, int index);
+USE_RET int model_finish(struct model *model, struct emu *emu);
 
 #endif /* MODEL_H */
diff --git a/src/emu/model_cpu.h b/src/emu/model_cpu.h
index 8b2ce51..7a4813b 100644
--- a/src/emu/model_cpu.h
+++ b/src/emu/model_cpu.h
@@ -11,6 +11,7 @@ struct model_cpu_spec;
 #include "track.h"
 #include "model.h"
 #include "model_chan.h"
+#include "common.h"
 
 struct model_cpu_spec {
 	size_t size;
@@ -24,7 +25,7 @@ struct model_cpu {
 	struct track *track;
 };
 
-int model_cpu_create(struct emu *emu, const struct model_cpu_spec *spec);
-int model_cpu_connect(struct emu *emu, const struct model_cpu_spec *spec);
+USE_RET int model_cpu_create(struct emu *emu, const struct model_cpu_spec *spec);
+USE_RET int model_cpu_connect(struct emu *emu, const struct model_cpu_spec *spec);
 
 #endif /* MODEL_CPU_H */
diff --git a/src/emu/model_pvt.h b/src/emu/model_pvt.h
index a944488..b3a01d0 100644
--- a/src/emu/model_pvt.h
+++ b/src/emu/model_pvt.h
@@ -6,6 +6,7 @@
 
 #include "emu.h"
 #include "pv/pcf.h"
+#include "common.h"
 
 struct model_pvt_spec {
 	const int *type;
@@ -18,7 +19,7 @@ struct model_pvt_spec {
 #include "model_cpu.h"
 #include "model_thread.h"
 
-int model_pvt_connect_cpu(struct emu *emu, const struct model_cpu_spec *spec);
-int model_pvt_connect_thread(struct emu *emu, const struct model_thread_spec *spec);
+USE_RET int model_pvt_connect_cpu(struct emu *emu, const struct model_cpu_spec *spec);
+USE_RET int model_pvt_connect_thread(struct emu *emu, const struct model_thread_spec *spec);
 
 #endif /* MODEL_PRV_H */
diff --git a/src/emu/model_thread.h b/src/emu/model_thread.h
index cc7614d..cfe7f23 100644
--- a/src/emu/model_thread.h
+++ b/src/emu/model_thread.h
@@ -11,6 +11,7 @@ struct model_thread_spec;
 #include "track.h"
 #include "model.h"
 #include "model_chan.h"
+#include "common.h"
 
 struct model_thread_spec {
 	size_t size;
@@ -25,7 +26,7 @@ struct model_thread {
 	struct track *track;
 };
 
-int model_thread_create(struct emu *emu, const struct model_thread_spec *spec);
-int model_thread_connect(struct emu *emu, const struct model_thread_spec *spec);
+USE_RET int model_thread_create(struct emu *emu, const struct model_thread_spec *spec);
+USE_RET int model_thread_connect(struct emu *emu, const struct model_thread_spec *spec);
 
 #endif /* MODEL_THREAD_H */
diff --git a/src/emu/models.h b/src/emu/models.h
index d999243..9cd4ca5 100644
--- a/src/emu/models.h
+++ b/src/emu/models.h
@@ -6,7 +6,6 @@
 
 #include "model.h"
 
-int
-models_register(struct model *model);
+USE_RET int models_register(struct model *model);
 
 #endif /* MODELS_H */
diff --git a/src/emu/path.h b/src/emu/path.h
index 486542e..1d845a7 100644
--- a/src/emu/path.h
+++ b/src/emu/path.h
@@ -4,12 +4,14 @@
 #ifndef PATH_H
 #define PATH_H
 
-int path_has_prefix(const char *path, const char *prefix);
-int path_count(const char *path, char c);
-int path_next(const char *path, char sep, const char (**next));
-int path_keep(char *path, int n);
-int path_strip(const char *path, int n, const char (**next));
-void path_remove_trailing(char *path);
-const char *path_filename(const char *path);
+#include "common.h"
+
+USE_RET int path_has_prefix(const char *path, const char *prefix);
+USE_RET int path_count(const char *path, char c);
+USE_RET int path_next(const char *path, char sep, const char (**next));
+USE_RET int path_keep(char *path, int n);
+USE_RET int path_strip(const char *path, int n, const char (**next));
+        void path_remove_trailing(char *path);
+USE_RET const char *path_filename(const char *path);
 
 #endif /* PATH_H */
diff --git a/src/emu/player.h b/src/emu/player.h
index db29e2d..837343d 100644
--- a/src/emu/player.h
+++ b/src/emu/player.h
@@ -22,11 +22,11 @@ struct player {
 	struct emu_ev ev;
 };
 
-int player_init(struct player *player, struct trace *trace, int unsorted);
-int player_step(struct player *player);
-struct emu_ev *player_ev(struct player *player);
-struct stream *player_stream(struct player *player);
-double player_progress(struct player *player);
-int64_t player_nprocessed(struct player *player);
+USE_RET int player_init(struct player *player, struct trace *trace, int unsorted);
+USE_RET int player_step(struct player *player);
+USE_RET struct emu_ev *player_ev(struct player *player);
+USE_RET struct stream *player_stream(struct player *player);
+USE_RET double player_progress(struct player *player);
+USE_RET int64_t player_nprocessed(struct player *player);
 
 #endif /* EMU_PLAYER_H */
diff --git a/src/emu/proc.h b/src/emu/proc.h
index 5504c11..af43b0e 100644
--- a/src/emu/proc.h
+++ b/src/emu/proc.h
@@ -44,16 +44,16 @@ struct proc {
 	struct extend ext;
 };
 
-int proc_relpath_get_pid(const char *relpath, int *pid);
-int proc_init_begin(struct proc *proc, const char *id);
-int proc_init_end(struct proc *proc);
-int proc_get_pid(struct proc *proc);
-void proc_set_gindex(struct proc *proc, int64_t gindex);
-void proc_set_loom(struct proc *proc, struct loom *loom);
-void proc_sort(struct proc *proc);
-int proc_load_metadata(struct proc *proc, JSON_Object *meta);
-struct thread *proc_find_thread(struct proc *proc, int tid);
-int proc_add_thread(struct proc *proc, struct thread *thread);
-void proc_sort(struct proc *proc);
+USE_RET int proc_relpath_get_pid(const char *relpath, int *pid);
+USE_RET int proc_init_begin(struct proc *proc, const char *id);
+USE_RET int proc_init_end(struct proc *proc);
+USE_RET int proc_get_pid(struct proc *proc);
+        void proc_set_gindex(struct proc *proc, int64_t gindex);
+        void proc_set_loom(struct proc *proc, struct loom *loom);
+        void proc_sort(struct proc *proc);
+USE_RET int proc_load_metadata(struct proc *proc, JSON_Object *meta);
+USE_RET struct thread *proc_find_thread(struct proc *proc, int tid);
+USE_RET int proc_add_thread(struct proc *proc, struct thread *thread);
+        void proc_sort(struct proc *proc);
 
 #endif /* PROC_H */
diff --git a/src/emu/recorder.h b/src/emu/recorder.h
index 9a12052..f3178b6 100644
--- a/src/emu/recorder.h
+++ b/src/emu/recorder.h
@@ -15,10 +15,10 @@ struct recorder {
 	struct pvt *pvt; /* Hash table by name */
 };
 
-int recorder_init(struct recorder *rec, const char *dir);
-struct pvt *recorder_find_pvt(struct recorder *rec, const char *name);
-struct pvt *recorder_add_pvt(struct recorder *rec, const char *name, long nrows);
-int recorder_advance(struct recorder *rec, int64_t time);
-int recorder_finish(struct recorder *rec);
+USE_RET int recorder_init(struct recorder *rec, const char *dir);
+USE_RET struct pvt *recorder_find_pvt(struct recorder *rec, const char *name);
+USE_RET struct pvt *recorder_add_pvt(struct recorder *rec, const char *name, long nrows);
+USE_RET int recorder_advance(struct recorder *rec, int64_t time);
+USE_RET int recorder_finish(struct recorder *rec);
 
 #endif /* RECORDER_H */
diff --git a/src/emu/stream.h b/src/emu/stream.h
index ea66a08..65d365e 100644
--- a/src/emu/stream.h
+++ b/src/emu/stream.h
@@ -1,8 +1,8 @@
 /* Copyright (c) 2021-2023 Barcelona Supercomputing Center (BSC)
  * SPDX-License-Identifier: GPL-3.0-or-later */
 
-#ifndef EMU_STREAM_H
-#define EMU_STREAM_H
+#ifndef STREAM_H
+#define STREAM_H
 
 #include "ovni.h"
 #include "heap.h"
@@ -36,19 +36,15 @@ struct stream {
 	double progress;
 };
 
-int stream_load(struct stream *stream,
-		const char *tracedir, const char *relpath);
+USE_RET int stream_load(struct stream *stream, const char *tracedir, const char *relpath);
+USE_RET int stream_clkoff_set(struct stream *stream, int64_t clock_offset);
+        void stream_progress(struct stream *stream, int64_t *done, int64_t *total);
+USE_RET int stream_step(struct stream *stream);
+USE_RET struct ovni_ev *stream_ev(struct stream *stream);
+USE_RET int64_t stream_evclock(struct stream *stream, struct ovni_ev *ev);
+USE_RET int64_t stream_lastclock(struct stream *stream);
+        void stream_allow_unsorted(struct stream *stream);
+        void stream_data_set(struct stream *stream, void *data);
+        void *stream_data_get(struct stream *stream);
 
-int stream_clkoff_set(struct stream *stream, int64_t clock_offset);
-
-void stream_progress(struct stream *stream, int64_t *done, int64_t *total);
-int stream_step(struct stream *stream);
-struct ovni_ev *stream_ev(struct stream *stream);
-int64_t stream_evclock(struct stream *stream, struct ovni_ev *ev);
-int64_t stream_lastclock(struct stream *stream);
-void stream_allow_unsorted(struct stream *stream);
-
-void stream_data_set(struct stream *stream, void *data);
-void *stream_data_get(struct stream *stream);
-
-#endif /* EMU_STREAM_H */
+#endif /* STREAM_H */
diff --git a/src/emu/system.h b/src/emu/system.h
index 4365533..0da1571 100644
--- a/src/emu/system.h
+++ b/src/emu/system.h
@@ -41,8 +41,8 @@ struct system {
 	struct lpt *lpt;
 };
 
-int system_init(struct system *sys, struct emu_args *args, struct trace *trace);
-int system_connect(struct system *sys, struct bay *bay, struct recorder *rec);
-struct lpt *system_get_lpt(struct stream *stream);
+USE_RET int system_init(struct system *sys, struct emu_args *args, struct trace *trace);
+USE_RET int system_connect(struct system *sys, struct bay *bay, struct recorder *rec);
+USE_RET struct lpt *system_get_lpt(struct stream *stream);
 
 #endif /* EMU_SYSTEM_H */
diff --git a/src/emu/task.h b/src/emu/task.h
index 6c81922..426b537 100644
--- a/src/emu/task.h
+++ b/src/emu/task.h
@@ -53,19 +53,16 @@ struct task_stack {
 	struct thread *thread;
 };
 
-struct task *task_find(struct task *tasks, uint32_t task_id);
-
-int task_create(struct task_info *info, uint32_t type_id, uint32_t task_id);
-int task_execute(struct task_stack *stack, struct task *task);
-int task_pause(struct task_stack *stack, struct task *task);
-int task_resume(struct task_stack *stack, struct task *task);
-int task_end(struct task_stack *stack, struct task *task);
-
-struct task_type *task_type_find(struct task_type *types, uint32_t type_id);
-int task_type_create(struct task_info *info, uint32_t type_id, const char *label);
-uint32_t task_get_type_gid(const char *label);
-
-int task_create_pcf_types(struct pcf_type *pcftype, struct task_type *types);
-struct task *task_get_running(struct task_stack *stack);
+USE_RET struct task *task_find(struct task *tasks, uint32_t task_id);
+USE_RET int task_create(struct task_info *info, uint32_t type_id, uint32_t task_id);
+USE_RET int task_execute(struct task_stack *stack, struct task *task);
+USE_RET int task_pause(struct task_stack *stack, struct task *task);
+USE_RET int task_resume(struct task_stack *stack, struct task *task);
+USE_RET int task_end(struct task_stack *stack, struct task *task);
+USE_RET struct task_type *task_type_find(struct task_type *types, uint32_t type_id);
+USE_RET int task_type_create(struct task_info *info, uint32_t type_id, const char *label);
+USE_RET uint32_t task_get_type_gid(const char *label);
+USE_RET int task_create_pcf_types(struct pcf_type *pcftype, struct task_type *types);
+USE_RET struct task *task_get_running(struct task_stack *stack);
 
 #endif /* TASK_H */
diff --git a/src/emu/thread.h b/src/emu/thread.h
index ee1fad2..b69d110 100644
--- a/src/emu/thread.h
+++ b/src/emu/thread.h
@@ -72,23 +72,21 @@ struct thread {
 	UT_hash_handle hh; /* threads in the process */
 };
 
-int thread_relpath_get_tid(const char *relpath, int *tid);
-int thread_init_begin(struct thread *thread, const char *relpath);
-int thread_init_end(struct thread *thread);
-int thread_set_state(struct thread *th, enum thread_state state);
-int thread_set_cpu(struct thread *th, struct cpu *cpu);
-int thread_unset_cpu(struct thread *th);
-int thread_migrate_cpu(struct thread *th, struct cpu *cpu);
-int thread_get_tid(struct thread *thread);
-void thread_set_gindex(struct thread *th, int64_t gindex);
-void thread_set_proc(struct thread *th, struct proc *proc);
-int thread_connect(struct thread *th, struct bay *bay, struct recorder *rec);
-
-int thread_select_active(struct mux *mux, struct value value, struct mux_input **input);
-int thread_select_running(struct mux *mux, struct value value, struct mux_input **input);
-int thread_select_any(struct mux *mux, struct value value, struct mux_input **input);
-
-int thread_create_pcf_types(struct pcf *pcf);
-struct pcf_type *thread_get_affinity_pcf_type(struct pcf *pcf);
+USE_RET int thread_relpath_get_tid(const char *relpath, int *tid);
+USE_RET int thread_init_begin(struct thread *thread, const char *relpath);
+USE_RET int thread_init_end(struct thread *thread);
+USE_RET int thread_set_state(struct thread *th, enum thread_state state);
+USE_RET int thread_set_cpu(struct thread *th, struct cpu *cpu);
+USE_RET int thread_unset_cpu(struct thread *th);
+USE_RET int thread_migrate_cpu(struct thread *th, struct cpu *cpu);
+USE_RET int thread_get_tid(struct thread *thread);
+        void thread_set_gindex(struct thread *th, int64_t gindex);
+        void thread_set_proc(struct thread *th, struct proc *proc);
+USE_RET int thread_connect(struct thread *th, struct bay *bay, struct recorder *rec);
+USE_RET int thread_select_active(struct mux *mux, struct value value, struct mux_input **input);
+USE_RET int thread_select_running(struct mux *mux, struct value value, struct mux_input **input);
+USE_RET int thread_select_any(struct mux *mux, struct value value, struct mux_input **input);
+USE_RET int thread_create_pcf_types(struct pcf *pcf);
+USE_RET struct pcf_type *thread_get_affinity_pcf_type(struct pcf *pcf);
 
 #endif /* THREAD_H */
diff --git a/src/emu/trace.h b/src/emu/trace.h
index a314739..8a5352a 100644
--- a/src/emu/trace.h
+++ b/src/emu/trace.h
@@ -15,6 +15,6 @@ struct trace {
 	struct stream *streams;
 };
 
-int trace_load(struct trace *trace, const char *tracedir);
+USE_RET int trace_load(struct trace *trace, const char *tracedir);
 
 #endif /* EMU_TRACE_H */
diff --git a/src/emu/track.h b/src/emu/track.h
index 1ecdce9..0dc514a 100644
--- a/src/emu/track.h
+++ b/src/emu/track.h
@@ -28,12 +28,10 @@ struct track {
 	struct mux mux;
 };
 
-int track_init(struct track *track, struct bay *bay, enum track_type type, int mode, const char *fmt, ...);
-int track_set_select(struct track *track, struct chan *sel, mux_select_func_t fsel, int64_t ninputs);
-int track_set_input(struct track *track, int64_t index, struct chan *inp);
-
-struct chan *track_get_output(struct track *track);
-
-int track_connect_thread(struct track *tracks, struct chan *chans, struct chan *sel, int n);
+USE_RET int track_init(struct track *track, struct bay *bay, enum track_type type, int mode, const char *fmt, ...);
+USE_RET int track_set_select(struct track *track, struct chan *sel, mux_select_func_t fsel, int64_t ninputs);
+USE_RET int track_set_input(struct track *track, int64_t index, struct chan *inp);
+USE_RET struct chan *track_get_output(struct track *track);
+USE_RET int track_connect_thread(struct track *tracks, struct chan *chans, struct chan *sel, int n);
 
 #endif /* TRACK_H */