Merge PR-2147 from sverker/sverker/enif-null-pid/OTP-15011

Add enif_set_pid_undefined & enif_is_pid_undefined

6 files changed, 182 insertions, 10 deletions

diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index d58ebd3171..cc7452bab5 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -783,14 +783,16 @@ typedef struct {
         <p>A process identifier (pid). In contrast to pid terms (instances of
           <c>ERL_NIF_TERM</c>), <c>ErlNifPid</c>s are self-contained and not
           bound to any <seealso marker="#ErlNifEnv">environment</seealso>.
-          <c>ErlNifPid</c> is an opaque type.</p>
+          <c>ErlNifPid</c> is an opaque type. It can be copied, moved
+	  in memory, forgotten, and so on.</p>
       </item>
       <tag><marker id="ErlNifPort"/><c>ErlNifPort</c></tag>
       <item>
         <p>A port identifier. In contrast to port ID terms (instances of
           <c>ERL_NIF_TERM</c>), <c>ErlNifPort</c>s are self-contained and not
           bound to any <seealso marker="#ErlNifEnv">environment</seealso>.
-          <c>ErlNifPort</c> is an opaque type.</p>
+	  <c>ErlNifPort</c> is an opaque type. It can be copied, moved
+	  in memory, forgotten, and so on.</p>
       </item>
       <tag><marker id="ErlNifResourceType"/><c>ErlNifResourceType</c></tag>
       <item>
@@ -1088,6 +1090,20 @@ typedef struct {
     </func>
 
     <func>
+      <name since="OTP @OTP-15011@"><ret>int</ret>
+      <nametext>enif_compare_pids(const ErlNifPid *pid1, const ErlNifPid *pid2)
+      </nametext></name>
+      <fsummary>Compare two pids.</fsummary>
+      <desc>
+        <p>Compares two <seealso marker="#ErlNifPid"><c>ErlNifPid</c>
+	  </seealso>s according to term order.</p>
+        <p>Returns <c>0</c> if <c>pid1</c> and <c>pid2</c> are equal,
+          &lt; <c>0</c> if <c>pid1</c> &lt; <c>pid2</c>, and
+          &gt; <c>0</c> if <c>pid1</c> &gt; <c>pid2</c>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name since="OTP R13B04"><ret>void</ret>
         <nametext>enif_cond_broadcast(ErlNifCond *cnd)</nametext></name>
       <fsummary></fsummary>
@@ -1392,6 +1408,9 @@ enif_free_iovec(iovec);]]></code>
           initializes the pid variable <c>*pid</c> from it and returns
           <c>true</c>. Otherwise returns <c>false</c>. No check is done to see
           if the process is alive.</p>
+	<note><p><c>enif_get_local_pid</c> will return false if argument
+	<c>term</c> is the atom <seealso marker="#enif_make_pid">
+	<c>undefined</c></seealso>.</p></note>
       </desc>
     </func>
 
@@ -1871,6 +1890,17 @@ enif_inspect_iovec(env, max_elements, term, &amp;tail, &amp;iovec);
     </func>
 
     <func>
+      <name since="OTP @OTP-15011@"><ret>int</ret>
+        <nametext>enif_is_pid_undefined(const ErlNifPid* pid)</nametext></name>
+      <fsummary>Determine if pid is undefined.</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c>pid</c> has been set as undefined by
+	<seealso marker="#enif_set_pid_undefined"><c>enif_set_pid_undefined</c>
+	</seealso>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name since="OTP R13B04"><ret>int</ret>
         <nametext>enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)</nametext>
       </name>
@@ -2259,7 +2289,8 @@ enif_inspect_iovec(env, max_elements, term, &amp;tail, &amp;iovec);
       </name>
       <fsummary>Make a pid term.</fsummary>
       <desc>
-        <p>Makes a pid term from <c>*pid</c>.</p>
+        <p>Makes a pid term or the atom <seealso marker="#enif_set_pid_undefined">
+	<c>undefined</c></seealso> from <c>*pid</c>.</p>
       </desc>
     </func>
 
@@ -2625,7 +2656,9 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
 	<p>Argument <c>caller_env</c> is the environment of the calling process
 	or callback. Must only be NULL if calling from a custom thread.</p>
         <p>Returns <c>0</c> on success, &lt; 0 if no <c>down</c> callback is
-          provided, and &gt; 0 if the process is no longer alive.</p>
+          provided, and &gt; 0 if the process is no longer alive or if
+	  <c>target_pid</c> is <seealso marker="#enif_set_pid_undefined">
+	  undefined</seealso>.</p>
         <p>This function is only thread-safe when the emulator with SMP support
           is used. It can only be used in a non-SMP emulator from a NIF-calling
           thread.</p>
@@ -3080,7 +3113,9 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
 	  <seealso marker="#enif_select_write"><c>enif_select_write</c></seealso>
 	  introduced in erts-11.0 (OTP-22.0).</p>
 	</note>
-	<p>Argument <c>pid</c> may be <c>NULL</c> to indicate the calling process.</p>
+	<p>Argument <c>pid</c> may be <c>NULL</c> to indicate the calling
+	  process. It must not be set as <seealso marker="#enif_set_pid_undefined">
+	  undefined</seealso>.</p>
 	<p>Argument <c>obj</c> is a resource object obtained from
           <seealso marker="#enif_alloc_resource"><c>enif_alloc_resource</c></seealso>.
 	  The purpose of the resource objects is as a container of the event object
@@ -3271,6 +3306,17 @@ if (retval &amp; ERL_NIF_SELECT_STOP_CALLED) {
     </func>
 
     <func>
+      <name since="OTP @OTP-15011@"><ret>void</ret>
+        <nametext>enif_set_pid_undefined(ErlNifPid* pid)</nametext></name>
+      <fsummary>Set pid as undefined.</fsummary>
+      <desc>
+        <p>Sets an <seealso marker="#ErlNifPid"><c>ErlNifPid</c></seealso>
+	variable as undefined. See <seealso marker="#enif_is_pid_undefined">
+	<c>enif_is_pid_undefined</c></seealso>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name since="OTP R13B04"><ret>unsigned</ret>
         <nametext>enif_sizeof_resource(void* obj)</nametext></name>
       <fsummary>Get the byte size of a resource object.</fsummary>
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index b2bd28fcbb..349d9bf13a 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1083,6 +1083,17 @@ int enif_get_local_pid(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPid* pid)
     return 0;
 }
 
+void enif_set_pid_undefined(ErlNifPid* pid)
+{
+    pid->pid = am_undefined;
+}
+
+int enif_is_pid_undefined(const ErlNifPid* pid)
+{
+    ASSERT(pid->pid == am_undefined || is_internal_pid(pid->pid));
+    return pid->pid == am_undefined;
+}
+
 int enif_get_local_port(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPort* port)
 {
     if (is_internal_port(term)) {
@@ -3341,6 +3352,9 @@ int enif_monitor_process(ErlNifEnv* env, void* obj, const ErlNifPid* target_pid,
     }
     ASSERT(rsrc->type->down);
 
+    if (target_pid->pid == am_undefined)
+        return 1;
+
     ref = erts_make_ref_in_buffer(tmp);
 
     mdp = erts_monitor_create(ERTS_MON_TYPE_RESOURCE, ref,
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 4ea6a2f7b0..8ab454c8dd 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -212,7 +212,8 @@ ERL_NIF_API_FUNC_DECL(int,enif_make_map_from_arrays,(ErlNifEnv *env, ERL_NIF_TER
 
 ERL_NIF_API_FUNC_DECL(int,enif_select_x,(ErlNifEnv* env, ErlNifEvent e, enum ErlNifSelectFlags flags, void* obj, const ErlNifPid* pid, ERL_NIF_TERM msg, ErlNifEnv* msg_env));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_monitor_term,(ErlNifEnv* env, const ErlNifMonitor*));
-
+ERL_NIF_API_FUNC_DECL(void,enif_set_pid_undefined,(ErlNifPid* pid));
+ERL_NIF_API_FUNC_DECL(int,enif_is_pid_undefined,(const ErlNifPid* pid));
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
@@ -398,6 +399,8 @@ ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_make_monitor_term,(ErlNifEnv* env, const
 #  define enif_make_map_from_arrays ERL_NIF_API_FUNC_MACRO(enif_make_map_from_arrays)
 #  define enif_select_x ERL_NIF_API_FUNC_MACRO(enif_select_x)
 #  define enif_make_monitor_term ERL_NIF_API_FUNC_MACRO(enif_make_monitor_term)
+#  define enif_set_pid_undefined ERL_NIF_API_FUNC_MACRO(enif_set_pid_undefined)
+#  define enif_is_pid_undefined ERL_NIF_API_FUNC_MACRO(enif_is_pid_undefined)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)
@@ -629,6 +632,7 @@ static ERL_NIF_INLINE ERL_NIF_TERM enif_make_list9(ErlNifEnv* env,
 #ifndef enif_make_pid
 
 #  define enif_make_pid(ENV, PID) ((void)(ENV),(const ERL_NIF_TERM)((PID)->pid))
+#  define enif_compare_pids(A, B) (enif_compare((A)->pid,(B)->pid))
 #  define enif_select_read(ENV, E, OBJ, PID, MSG, MSG_ENV) \
     enif_select_x(ENV, E, ERL_NIF_SELECT_READ | ERL_NIF_SELECT_CUSTOM_MSG, \
                   OBJ, PID, MSG, MSG_ENV)
diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index a699ece23e..80e8030d74 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -1181,6 +1181,7 @@ enif_select_x(ErlNifEnv* env,
 
     if (on) {
         const Eterm recipient = pid ? pid->pid : env->proc->common.id;
+        ASSERT(is_internal_pid(recipient));
         if (!state->driver.nif)
             state->driver.nif = alloc_nif_select_data();
         if (state->type == ERTS_EV_TYPE_NONE) {
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index 168df76301..4a0ad9c1d5 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -64,7 +64,8 @@
          nif_phash2/1,
          nif_whereis/1, nif_whereis_parallel/1,
          nif_whereis_threaded/1, nif_whereis_proxy/1,
-         nif_ioq/1
+         nif_ioq/1,
+         pid/1
 	]).
 
 -export([many_args_100/100]).
@@ -103,7 +104,8 @@ all() ->
      nif_internal_hash_salted,
      nif_phash2,
      nif_whereis, nif_whereis_parallel, nif_whereis_threaded,
-     nif_ioq].
+     nif_ioq,
+     pid].
 
 groups() ->
     [{G, [], api_repeaters()} || G <- api_groups()]
@@ -3367,6 +3369,30 @@ make_unaligned_binary(Bin0) ->
     <<0:3,Bin:Size/binary,31:5>> = id(<<0:3,Bin0/binary,31:5>>),
     Bin.
 
+pid(Config) ->
+    ensure_lib_loaded(Config),
+    Self = self(),
+    {true, ErlNifPid} = get_local_pid_nif(Self),
+    false = is_pid_undefined_nif(ErlNifPid),
+    Self = make_pid_nif(ErlNifPid),
+
+    UndefPid = set_pid_undefined_nif(),
+    true = is_pid_undefined_nif(UndefPid),
+    undefined = make_pid_nif(UndefPid),
+    0 = send_term(UndefPid, message),
+
+    Other = spawn(fun() -> ok end),
+    {true,OtherNifPid} = get_local_pid_nif(Other),
+    Cmp = compare_pids_nif(ErlNifPid, OtherNifPid),
+    true = if Cmp < 0 -> Self < Other;
+              Cmp > 0 -> Self > Other
+           end,
+    0 = compare_pids_nif(ErlNifPid, ErlNifPid),
+
+    {false, _} = get_local_pid_nif(undefined),
+    ok.
+
+
 id(I) -> I.
 
 %% The NIFs:
@@ -3475,5 +3501,11 @@ convert_time_unit(_,_,_) -> ?nif_stub.
 now_time() -> ?nif_stub.
 cpu_time() -> ?nif_stub.
 
+get_local_pid_nif(_) -> ?nif_stub.
+make_pid_nif(_) -> ?nif_stub.
+set_pid_undefined_nif() -> ?nif_stub.
+is_pid_undefined_nif(_) -> ?nif_stub.
+compare_pids_nif(_, _) -> ?nif_stub.
+
 nif_stub_error(Line) ->
     exit({nif_not_loaded,module,?MODULE,line,Line}).
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index af2d062857..0d5d900d31 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -1882,12 +1882,23 @@ static ERL_NIF_TERM copy_blob(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[
     return enif_make_copy(env, mti.p->blob);
 }
 
+static int get_pidbin(ErlNifEnv* env, ERL_NIF_TERM pidbin, ErlNifPid* pid)
+{
+    ErlNifBinary bin;
+
+    if (!enif_inspect_binary(env, pidbin, &bin) || bin.size != sizeof(ErlNifPid))
+        return 0;
+
+    memcpy(pid, bin.data, bin.size);
+    return 1;
+}
+
 static ERL_NIF_TERM send_term(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 {
     ErlNifEnv* menv;
     ErlNifPid pid;
     int ret;
-    if (!enif_get_local_pid(env, argv[0], &pid)) {
+    if (!enif_get_local_pid(env, argv[0], &pid) && !get_pidbin(env, argv[0], &pid)) {
 	return enif_make_badarg(env);
     }
     menv = enif_alloc_env();
@@ -3513,6 +3524,65 @@ static ERL_NIF_TERM ioq(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
     return enif_make_badarg(env);
 }
 
+static ERL_NIF_TERM make_bool(ErlNifEnv* env, int bool)
+{
+    return bool ? atom_true : atom_false;
+}
+
+static ERL_NIF_TERM get_local_pid_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifPid pid;
+    ERL_NIF_TERM pid_bin;
+    int ret = enif_get_local_pid(env, argv[0], &pid);
+
+    memcpy(enif_make_new_binary(env, sizeof(ErlNifPid), &pid_bin),
+           &pid, sizeof(ErlNifPid));
+
+    return enif_make_tuple2(env, make_bool(env, ret), pid_bin);
+}
+
+static ERL_NIF_TERM make_pid_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifPid pid;
+
+    if (!get_pidbin(env, argv[0], &pid))
+        return enif_make_badarg(env);
+
+    return enif_make_pid(env, &pid);
+}
+
+static ERL_NIF_TERM set_pid_undefined_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifPid pid;
+    ERL_NIF_TERM pid_bin;
+
+    enif_set_pid_undefined(&pid);
+    memcpy(enif_make_new_binary(env, sizeof(ErlNifPid), &pid_bin),
+           &pid, sizeof(ErlNifPid));
+
+    return pid_bin;
+}
+
+static ERL_NIF_TERM is_pid_undefined_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifPid pid;
+
+    if (!get_pidbin(env, argv[0], &pid))
+        return enif_make_badarg(env);
+
+    return make_bool(env, enif_is_pid_undefined(&pid));
+}
+
+static ERL_NIF_TERM compare_pids_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifPid a, b;
+
+    if (!get_pidbin(env, argv[0], &a) || !get_pidbin(env, argv[1], &b))
+        return enif_make_badarg(env);
+
+    return enif_make_int(env, enif_compare_pids(&a, &b));
+}
+
 static ErlNifFunc nif_funcs[] =
 {
     {"lib_version", 0, lib_version},
@@ -3615,7 +3685,12 @@ static ErlNifFunc nif_funcs[] =
     {"ioq_nif", 1, ioq},
     {"ioq_nif", 2, ioq},
     {"ioq_nif", 3, ioq},
-    {"ioq_nif", 4, ioq}
+    {"ioq_nif", 4, ioq},
+    {"get_local_pid_nif", 1, get_local_pid_nif},
+    {"make_pid_nif", 1, make_pid_nif},
+    {"set_pid_undefined_nif", 0, set_pid_undefined_nif},
+    {"is_pid_undefined_nif", 1, is_pid_undefined_nif},
+    {"compare_pids_nif", 2, compare_pids_nif}
 };
 
 ERL_NIF_INIT(nif_SUITE,nif_funcs,load,NULL,upgrade,unload)