erts: Change return value for enif_select

to negative int as error and positive as success.

8 files changed, 38 insertions, 37 deletions

diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 9800a530f2..e8e7bd4a80 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -2583,7 +2583,7 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
     </func>
 
     <func>
-      <name><ret>enum ErlNifSelectReturn</ret>
+      <name><ret>int</ret>
         <nametext>enif_select(ErlNifEnv* env, ErlNifEvent event, enum ErlNifSelectFlags mode,
 	void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref)</nametext>
       </name>
@@ -2626,36 +2626,36 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
 	  the event object. This safe way of closing event objects must be used
 	  even if all notifications have been received and no further calls to
 	  <c>enif_select</c> have been made.</p>
-	<p>Returns an integer where different bits indicate the outcome of the call:</p>
+	<p>Returns a non-negative value on success where the following bits can be set:</p>
         <taglist>
-          <tag><c>ERL_NIF_SELECT_ERROR</c></tag>
-          <item>The master error bit. It will always be set if the call failed for
-	    any reason.</item>
           <tag><c>ERL_NIF_SELECT_STOP_CALLED</c></tag>
           <item>The stop callback was called directly by <c>enif_select</c>.</item>
           <tag><c>ERL_NIF_SELECT_STOP_SCHEDULED</c></tag>
           <item>The stop callback was scheduled to run on some other thread
 	    or later by this thread.</item>
+	</taglist>
+	<p>Returns a negative value if the call failed where the follwing bits can be set:</p>
+        <taglist>
           <tag><c>ERL_NIF_SELECT_INVALID_EVENT</c></tag>
           <item>Argument <c>event</c> is not a valid OS event object.</item>
           <tag><c>ERL_NIF_SELECT_FAILED</c></tag>
           <item>The system call failed to add the event object to the poll set.</item>
         </taglist>
-	<p>The return value from a successful call with <c>mode</c> as <c>ERL_NIF_SELECT_STOP</c>,
-	will contain either bit <c>ERL_NIF_SELECT_STOP_CALLED</c> or
-	<c>ERL_NIF_SELECT_STOP_SCHEDULED</c>.</p>
         <note>
-          <p>Always use bitwise AND to test the return value. New significant bits
-	  may be added in future releases to give more detailed information for both
-	  failed and successful calls. Do NOT use equallity tests like <c>==</c>, as
-	  that may cause your application to stop working.</p>
+          <p>Use bitwise AND to test for specific bits in the return vaue.
+	  New significant bits may be added in future releases to give more detailed
+	  information for both failed and successful calls. Do NOT use equallity tests
+	  like <c>==</c>, as that may cause your application to stop working.</p>
 	  <p>Example:</p>
 	  <code type="none">
-retval = enif_select(env, fd, ERL_NIF_SELECT_READ, resource, ref);
-if (retval &amp; ERL_NIF_SELECT_ERROR) {
+retval = enif_select(env, fd, ERL_NIF_SELECT_STOP, resource, ref);
+if (retval < 0) {
     /* handle error */
 }
 /* Success! */
+if (retval &amp; ERL_NIF_SELECT_STOP_CALLED) {
+    /* ... */
+}
 </code>
         </note>
       </desc>
diff --git a/erts/emulator/beam/erl_drv_nif.h b/erts/emulator/beam/erl_drv_nif.h
index 8de4a7855d..2d21dac87a 100644
--- a/erts/emulator/beam/erl_drv_nif.h
+++ b/erts/emulator/beam/erl_drv_nif.h
@@ -56,14 +56,6 @@ enum ErlNifSelectFlags {
     ERL_NIF_SELECT_STOP      = (1 << 2)
 };
 
-enum ErlNifSelectReturn {
-    ERL_NIF_SELECT_ERROR          = (1 << 0),
-    ERL_NIF_SELECT_STOP_CALLED    = (1 << 1),
-    ERL_NIF_SELECT_STOP_SCHEDULED = (1 << 2),
-    ERL_NIF_SELECT_INVALID_EVENT  = (1 << 3),
-    ERL_NIF_SELECT_FAILED         = (1 << 4)
-};
-
 /*
  * A driver monitor
  */
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index 5248f287ee..9ff28a30cc 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -142,6 +142,12 @@ typedef struct
 typedef int ErlNifEvent; /* An event to be selected on. */
 //#endif
 
+/* Return bits from enif_select: */
+#define ERL_NIF_SELECT_STOP_CALLED    (1 << 0)
+#define ERL_NIF_SELECT_STOP_SCHEDULED (1 << 1)
+#define ERL_NIF_SELECT_INVALID_EVENT  (1 << 2)
+#define ERL_NIF_SELECT_FAILED         (1 << 3)
+
 typedef enum
 {
     ERL_NIF_RT_CREATE = 1,
diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 089f10fd8e..2964b09b8c 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -1198,7 +1198,7 @@ done_unknown:
     return ret;
 }
 
-enum ErlNifSelectReturn
+int
 ERTS_CIO_EXPORT(enif_select)(ErlNifEnv* env,
                              ErlNifEvent e,
                              enum ErlNifSelectFlags mode,
@@ -1213,7 +1213,7 @@ ERTS_CIO_EXPORT(enif_select)(ErlNifEnv* env,
     ErtsPollEvents new_events, old_events;
     ErtsDrvEventState *state;
     int wake_poller;
-    enum ErlNifSelectReturn ret;
+    int ret;
     enum { NO_STOP=0, CALL_STOP, CALL_STOP_AND_RELEASE } call_stop = NO_STOP;
 #if ERTS_CIO_HAVE_DRV_EVENT
     ErtsDrvEventDataState *free_event = NULL;
@@ -1229,11 +1229,11 @@ ERTS_CIO_EXPORT(enif_select)(ErlNifEnv* env,
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
     if ((unsigned)fd >= (unsigned)erts_smp_atomic_read_nob(&drv_ev_state_len)) {
 	if (fd < 0) {
-	    return ERL_NIF_SELECT_ERROR | ERL_NIF_SELECT_INVALID_EVENT;
+	    return INT_MIN | ERL_NIF_SELECT_INVALID_EVENT;
 	}
 	if (fd >= max_fds) {
 	    nif_select_large_fd_error(fd, mode, resource, ref);
-            return ERL_NIF_SELECT_ERROR | ERL_NIF_SELECT_INVALID_EVENT;
+            return INT_MIN | ERL_NIF_SELECT_INVALID_EVENT;
 	}
 	grow_drv_ev_state(fd);
     }
@@ -1327,7 +1327,7 @@ ERTS_CIO_EXPORT(enif_select)(ErlNifEnv* env,
             state->driver.nif->out.ddeselect_cnt = 0;
             state->driver.stop.resource = NULL;
 	}
-	ret = ERL_NIF_SELECT_ERROR | ERL_NIF_SELECT_FAILED;
+	ret = INT_MIN | ERL_NIF_SELECT_FAILED;
 	goto done;
     }
 
@@ -2518,6 +2518,10 @@ static void drv_ev_state_free(void *des)
 void
 ERTS_CIO_EXPORT(erts_init_check_io)(void)
 {
+    ERTS_CT_ASSERT((INT_MIN & (ERL_NIF_SELECT_STOP_CALLED |
+                               ERL_NIF_SELECT_STOP_SCHEDULED |
+                               ERL_NIF_SELECT_INVALID_EVENT |
+                               ERL_NIF_SELECT_FAILED)) == 0);
     erts_smp_atomic_init_nob(&erts_check_io_time, 0);
     erts_smp_atomic_init_nob(&pollset.in_poll_wait, 0);
 
diff --git a/erts/emulator/sys/common/erl_check_io.h b/erts/emulator/sys/common/erl_check_io.h
index 4f9efeefcd..f02d6c1f62 100644
--- a/erts/emulator/sys/common/erl_check_io.h
+++ b/erts/emulator/sys/common/erl_check_io.h
@@ -34,8 +34,8 @@
 
 int driver_select_kp(ErlDrvPort, ErlDrvEvent, int, int);
 int driver_select_nkp(ErlDrvPort, ErlDrvEvent, int, int);
-enum ErlNifSelectReturn enif_select_kp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
-enum ErlNifSelectReturn enif_select_nkp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
+int enif_select_kp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
+int enif_select_nkp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
 int driver_event_kp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
 int driver_event_nkp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
 Uint erts_check_io_size_kp(void);
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 4843ee4ba2..f4bdc129e1 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -161,7 +161,7 @@ int erts_use_kernel_poll = 0;
 
 struct {
     int (*select)(ErlDrvPort, ErlDrvEvent, int, int);
-    enum ErlNifSelectReturn (*enif_select)(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
+    int (*enif_select)(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, const ErlNifPid*, Eterm);
     int (*event)(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
     void (*check_io_as_interrupt)(void);
     void (*check_io_interrupt)(int);
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index de26e73c3d..d88ac01e46 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -457,11 +457,10 @@ t_on_load(Config) when is_list(Config) ->
 -define(ERL_NIF_SELECT_WRITE, (1 bsl 1)).
 -define(ERL_NIF_SELECT_STOP, (1 bsl 2)).
 
--define(ERL_NIF_SELECT_ERROR, (1 bsl 0)).
--define(ERL_NIF_SELECT_STOP_CALLED, (1 bsl 1)).
--define(ERL_NIF_SELECT_STOP_SCHEDULED, (1 bsl 2)).
--define(ERL_NIF_SELECT_INVALID_EVENT, (1 bsl 3)).
--define(ERL_NIF_SELECT_FAILED, (1 bsl 4)).
+-define(ERL_NIF_SELECT_STOP_CALLED, (1 bsl 0)).
+-define(ERL_NIF_SELECT_STOP_SCHEDULED, (1 bsl 1)).
+-define(ERL_NIF_SELECT_INVALID_EVENT, (1 bsl 2)).
+-define(ERL_NIF_SELECT_FAILED, (1 bsl 3)).
 
 
 select(Config) when is_list(Config) ->
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index 6cf02c6efe..05b4b05e16 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -2123,7 +2123,7 @@ static ERL_NIF_TERM select_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv
     void* obj;
     ErlNifPid nifpid, *pid = NULL;
     ERL_NIF_TERM ref;
-    enum ErlNifSelectReturn retval;
+    int retval;
 
     if (!get_fd(env, argv[0], &fdr)
         || !enif_get_uint(env, argv[1], &mode)
@@ -2143,7 +2143,7 @@ static ERL_NIF_TERM select_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv
     enif_self(env, &fdr->pid);
     retval = enif_select(env, fdr->fd, mode, obj, pid, ref);
 
-    return enif_make_int(env, (int)retval);
+    return enif_make_int(env, retval);
 }
 
 static ERL_NIF_TERM pipe_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])