Add enif_raise_exception

Add enif_raise_exception function to allow NIFs to raise error
exceptions holding any Erlang terms. This does not replace or
deprecate the enif_make_badarg function, though, because raising
badarg errors is so idiomatic in NIFs. Reimplement enif_make_badarg on
top of enif_raise_exception. Add new tests for enif_raise_exception
for both normal and dirty NIFs. Add documentation for
enif_raise_exception.

5 files changed, 123 insertions, 50 deletions

diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 155aee2f42..104d90c937 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -787,7 +787,8 @@ typedef enum {
       <seealso marker="#enif_make_badarg">enif_make_badarg</seealso> is called to set a
       pending <c>badarg</c> exception, a subsequent call to <c>enif_has_pending_exception(env, &amp;reason)</c>
       will set <c>reason</c> to the atom <c>badarg</c>, then return true.</p>
-      <p>See also: <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.</p>
+      <p>See also: <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>
+      and <seealso marker="#enif_raise_exception">enif_raise_exception</seealso>.</p>
       </desc>
     </func>
     <func><name><ret>int</ret><nametext>enif_inspect_binary(ErlNifEnv* env, ERL_NIF_TERM bin_term, ErlNifBinary* bin)</nametext></name>
@@ -902,12 +903,13 @@ typedef enum {
       it calls invokes <c>enif_make_badarg</c>, the runtime ensures that a
       <c>badarg</c> exception is raised when the NIF returns, even if the NIF
       attempts to return a non-exception term instead.
-      The return value from <c>enif_make_badarg</c> may only be used as
-      return value from the NIF that invoked it (direct or indirectly)
+      The return value from <c>enif_make_badarg</c> may be used only as the
+      return value from the NIF that invoked it (directly or indirectly)
       or be passed to
       <seealso marker="#enif_is_exception">enif_is_exception</seealso>, but
       not to any other NIF API function.</p>
-      <p>See also: <seealso marker="#enif_has_pending_exception">enif_has_pending_exception</seealso>.
+      <p>See also: <seealso marker="#enif_has_pending_exception">enif_has_pending_exception</seealso>
+      and <seealso marker="#enif_raise_exception">enif_raise_exception</seealso>
       </p>
       <note><p>In earlier versions (older than erts-7.0, OTP 18) the return value
       from <c>enif_make_badarg</c> had to be returned from the NIF. This
@@ -1174,6 +1176,19 @@ typedef enum {
       <c>reload</c> or <c>upgrade</c>.</p>
       <p>Was previously named <c>enif_get_data</c>.</p></desc>
     </func>
+    <func><name><ret>ERL_NIF_TERM</ret><nametext>enif_raise_exception(ErlNifEnv* env, ERL_NIF_TERM reason)</nametext></name>
+      <fsummary>Raise a NIF error exception</fsummary>
+      <desc><p>Create an error exception with the term <c>reason</c> to be returned from a NIF,
+      and associate it with the environment <c>env</c>. Once a NIF or any function it calls
+      invokes <c>enif_raise_exception</c>, the runtime ensures that the exception it creates
+      is raised when the NIF returns, even if the NIF attempts to return a non-exception
+      term instead. The return value from <c>enif_raise_exception</c> may be used only as
+      the return value from the NIF that invoked it (directly or indirectly) or be passed
+      to <seealso marker="#enif_is_exception">enif_is_exception</seealso>, but
+      not to any other NIF API function.</p>
+      <p>See also: <seealso marker="#enif_has_pending_exception">enif_has_pending_exception</seealso>
+      and <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.</p></desc>
+    </func>
     <func><name><ret>int</ret><nametext>enif_realloc_binary(ErlNifBinary* bin, size_t size)</nametext></name>
       <fsummary>Change the size of a binary.</fsummary>
       <desc><p>Change the size of a binary <c>bin</c>. The source binary
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 36da6519f7..8c222a6db7 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -737,14 +737,20 @@ Eterm enif_make_sub_binary(ErlNifEnv* env, ERL_NIF_TERM bin_term,
 
 Eterm enif_make_badarg(ErlNifEnv* env)
 {
+    return enif_raise_exception(env, am_badarg);
+}
+
+Eterm enif_raise_exception(ErlNifEnv* env, ERL_NIF_TERM reason)
+{
     env->exception_thrown = 1;
-    BIF_ERROR(env->proc, BADARG);
+    env->proc->fvalue = reason;
+    BIF_ERROR(env->proc, EXC_ERROR);
 }
 
 int enif_has_pending_exception(ErlNifEnv* env, ERL_NIF_TERM* reason)
 {
     if (env->exception_thrown && reason != NULL) {
-	*reason = am_badarg;
+	*reason = env->proc->fvalue;
     }
     return env->exception_thrown;
 }
@@ -1541,12 +1547,13 @@ int enif_consume_timeslice(ErlNifEnv* env, int percent)
  * NIF exports need a few more items than the Export struct provides,
  * including the erl_module_nif* and a NIF function pointer, so the
  * NifExport below adds those. The Export member must be first in the
- * struct. The saved_mfa, saved_argc, nif_level, alloced_argv_sz and argv
- * members are used to track the MFA and arguments of the top NIF in case a
- * chain of one or more enif_schedule_nif() calls results in an exception,
- * since in that case the original MFA and registers have to be restored
- * before returning to Erlang to ensure stacktrace information associated
- * with the exception is correct.
+ * struct. The saved_mfa, exception_thrown, saved_argc, rootset_extra, and
+ * rootset members are used to track the MFA, any pending exception, and
+ * arguments of the top NIF in case a chain of one or more
+ * enif_schedule_nif() calls results in an exception, since in that case
+ * the original MFA and registers have to be restored before returning to
+ * Erlang to ensure stacktrace information associated with the exception is
+ * correct.
  */
 typedef ERL_NIF_TERM (*NativeFunPtr)(ErlNifEnv*, int, const ERL_NIF_TERM[]);
 
@@ -1555,25 +1562,28 @@ typedef struct {
     struct erl_module_nif* m;
     NativeFunPtr fp;
     Eterm saved_mfa[3];
+    int exception_thrown;
     int saved_argc;
-    int alloced_argv_sz;
-    Eterm argv[1];
+    int rootset_extra;
+    Eterm rootset[1];
 } NifExport;
 
 /*
  * If a process has saved arguments, they need to be part of the GC
  * rootset. The function below is called from setup_rootset() in
- * erl_gc.c. This function is declared in erl_process.h.
+ * erl_gc.c. This function is declared in erl_process.h. Any exception term
+ * saved in the NifExport is also made part of the GC rootset here; it
+ * always resides in rootset[0].
  */
 int
 erts_setup_nif_gc(Process* proc, Eterm** objv, int* nobj)
 {
     NifExport* ep = (NifExport*) ERTS_PROC_GET_NIF_TRAP_EXPORT(proc);
-    int gc = (ep && ep->saved_argc > 0);
+    int gc = ep && (ep->saved_argc > 0 || ep->rootset[0] != NIL);
 
     if (gc) {
-	*objv = ep->argv;
-	*nobj = ep->saved_argc;
+	*objv = ep->rootset;
+	*nobj = 1 + ep->saved_argc;
     }
     return gc;
 }
@@ -1585,14 +1595,14 @@ static NifExport*
 allocate_nif_sched_data(Process* proc, int argc)
 {
     NifExport* ep;
-    size_t argv_extra, total;
+    size_t total;
     int i;
 
-    argv_extra = argc > 1 ? sizeof(Eterm)*(argc-1) : 0;
-    total = sizeof(NifExport) + argv_extra;
+    total = sizeof(NifExport) + argc*sizeof(Eterm);
     ep = erts_alloc(ERTS_ALC_T_NIF_TRAP_EXPORT, total);
     sys_memset((void*) ep, 0, total);
-    ep->alloced_argv_sz = argc;
+    ep->rootset_extra = argc;
+    ep->rootset[0] = NIL;
     for (i=0; i<ERTS_NUM_CODE_IX; i++) {
 	ep->exp.addressv[i] = &ep->exp.code[3];
     }
@@ -1633,15 +1643,22 @@ init_nif_sched_data(ErlNifEnv* env, NativeFunPtr direct_fp, NativeFunPtr indirec
     ep = (NifExport*) ERTS_PROC_GET_NIF_TRAP_EXPORT(proc);
     if (!ep)
 	ep = allocate_nif_sched_data(proc, argc);
-    else if (need_save && ep->alloced_argv_sz < argc) {
+    else if (need_save && ep->rootset_extra < argc) {
 	NifExport* new_ep = allocate_nif_sched_data(proc, argc);
 	destroy_nif_export(ep);
 	ep = new_ep;
     }
+    if (env->exception_thrown) {
+	ep->exception_thrown = 1;
+	ep->rootset[0] = env->proc->fvalue;
+    } else {
+	ep->exception_thrown = 0;
+	ep->rootset[0] = NIL;
+    }
     ERTS_VBUMP_ALL_REDS(proc);
     for (i = 0; i < argc; i++) {
 	if (need_save)
-	    ep->argv[i] = reg[i];
+	    ep->rootset[i+1] = reg[i];
 	reg[i] = (Eterm) argv[i];
     }
     if (need_save) {
@@ -1677,7 +1694,7 @@ restore_nif_mfa(Process* proc, NifExport* ep, int exception)
     proc->current[2] = ep->saved_mfa[2];
     if (exception)
 	for (i = 0; i < ep->saved_argc; i++)
-	    reg[i] = ep->argv[i];
+	    reg[i] = ep->rootset[i+1];
     ep->saved_argc = 0;
     ep->saved_mfa[0] = THE_NON_VALUE;
 }
@@ -1702,6 +1719,7 @@ dirty_nif_finalizer(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
     ASSERT(!ERTS_SCHEDULER_IS_DIRTY(env->proc->scheduler_data));
     ep = (NifExport*) ERTS_PROC_GET_NIF_TRAP_EXPORT(proc);
     ASSERT(ep);
+    ASSERT(!ep->exception_thrown);
     if (ep->fp)
 	restore_nif_mfa(proc, ep, 0);
     return argv[0];
@@ -1719,9 +1737,10 @@ dirty_nif_exception(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
     ASSERT(!ERTS_SCHEDULER_IS_DIRTY(env->proc->scheduler_data));
     ep = (NifExport*) ERTS_PROC_GET_NIF_TRAP_EXPORT(proc);
     ASSERT(ep);
+    ASSERT(ep->exception_thrown);
     if (ep->fp)
 	restore_nif_mfa(proc, ep, 1);
-    return enif_make_badarg(env);
+    return enif_raise_exception(env, ep->rootset[0]);
 }
 
 /*
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index fe25c803ec..e38a016958 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -157,6 +157,7 @@ ERL_NIF_API_FUNC_DECL(int, enif_map_iterator_prev, (ErlNifEnv *env, ErlNifMapIte
 ERL_NIF_API_FUNC_DECL(int, enif_map_iterator_get_pair, (ErlNifEnv *env, ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM *value));
 ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM,enif_schedule_nif,(ErlNifEnv*,const char*,int,ERL_NIF_TERM (*)(ErlNifEnv*,int,const ERL_NIF_TERM[]),int,const ERL_NIF_TERM[]));
 ERL_NIF_API_FUNC_DECL(int, enif_has_pending_exception, (ErlNifEnv *env, ERL_NIF_TERM* reason));
+ERL_NIF_API_FUNC_DECL(ERL_NIF_TERM, enif_raise_exception, (ErlNifEnv *env, ERL_NIF_TERM reason));
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
@@ -307,6 +308,7 @@ ERL_NIF_API_FUNC_DECL(int,enif_is_on_dirty_scheduler,(ErlNifEnv*));
 #  define enif_map_iterator_get_pair ERL_NIF_API_FUNC_MACRO(enif_map_iterator_get_pair)
 #  define enif_schedule_nif ERL_NIF_API_FUNC_MACRO(enif_schedule_nif)
 #  define enif_has_pending_exception ERL_NIF_API_FUNC_MACRO(enif_has_pending_exception)
+#  define enif_raise_exception ERL_NIF_API_FUNC_MACRO(enif_raise_exception)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index 434d1c38d0..778f6fd087 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -39,8 +39,9 @@
 	 get_length/1, make_atom/1, make_string/1, reverse_list_test/1,
 	 otp_9828/1,
 	 otp_9668/1, consume_timeslice/1, dirty_nif/1, dirty_nif_send/1,
-	 dirty_nif_exception/1, nif_schedule/1,
-	 nif_exception/1, nif_nan_and_inf/1, nif_atom_too_long/1
+	 dirty_nif_exception/1, call_dirty_nif_exception/1, nif_schedule/1,
+	 nif_exception/1, call_nif_exception/1,
+	 nif_nan_and_inf/1, nif_atom_too_long/1
 	]).
 
 -export([many_args_100/100]).
@@ -1621,7 +1622,10 @@ dirty_nif_exception(Config) when is_list(Config) ->
 		    [{?MODULE,call_dirty_nif_exception,[0],_}|_] =
 			erlang:get_stacktrace(),
 		    ok
-	    end
+	    end,
+	    %% this checks that a dirty NIF can raise various terms as
+	    %% exceptions
+	    ok = nif_raise_exceptions(call_dirty_nif_exception)
     catch
 	error:badarg ->
 	    {skipped,"No dirty scheduler support"}
@@ -1633,12 +1637,15 @@ nif_exception(Config) when is_list(Config) ->
 	%% this checks that the expected exception occurs when the NIF
 	%% calls enif_make_badarg at some point but then tries to return a
 	%% value that isn't an exception
-	call_nif_exception(),
+	call_nif_exception(0),
 	?t:fail(expected_badarg)
     catch
 	error:badarg ->
 	    ok
-    end.
+    end,
+    %% this checks that a NIF can raise various terms as exceptions
+    ok = nif_raise_exceptions(call_nif_exception),
+    ok.
 
 nif_nan_and_inf(Config) when is_list(Config) ->
     ensure_lib_loaded(Config),
@@ -1760,7 +1767,20 @@ check(Exp,Got,Line) ->
   	    io:format("CHECK at ~p: Expected ~p but got ~p\n",[Line,Exp,Got]),
  	    Got
     end.
-	    
+
+nif_raise_exceptions(NifFunc) ->
+    ExcTerms = [{error, test}, "a string", <<"a binary">>,
+		42, [1,2,3,4,5], [{p,1},{p,2},{p,3}]],
+    lists:foldl(fun(Term, ok) ->
+			try
+			    erlang:apply(?MODULE,NifFunc,[Term]),
+			    ?t:fail({expected,Term})
+			catch
+			    error:Term ->
+				[{?MODULE,NifFunc,[Term],_}|_] = erlang:get_stacktrace(),
+				ok
+			end
+		end, ok, ExcTerms).
 
 %% The NIFs:
 lib_version() -> undefined.
@@ -1816,7 +1836,7 @@ call_dirty_nif(_,_,_) -> ?nif_stub.
 send_from_dirty_nif(_) -> ?nif_stub.
 call_dirty_nif_exception(_) -> ?nif_stub.
 call_dirty_nif_zero_args() -> ?nif_stub.
-call_nif_exception() -> ?nif_stub.
+call_nif_exception(_) -> ?nif_stub.
 call_nif_nan_or_inf(_) -> ?nif_stub.
 call_nif_atom_too_long(_) -> ?nif_stub.
 
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index 95e361690f..0191e098db 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -1618,13 +1618,18 @@ static ERL_NIF_TERM call_dirty_nif_exception(ErlNifEnv* env, int argc, const ERL
 {
     switch (argc) {
     case 1: {
-	ERL_NIF_TERM args[255];
-	int i;
-	args[0] = argv[0];
-	for (i = 1; i < 255; i++)
-	    args[i] = enif_make_int(env, i);
-	return enif_schedule_nif(env, "call_dirty_nif_exception", ERL_NIF_DIRTY_JOB_CPU_BOUND,
-				 call_dirty_nif_exception, 255, args);
+	int arg;
+	if (enif_get_int(env, argv[0], &arg) && arg < 2) {
+	    ERL_NIF_TERM args[255];
+	    int i;
+	    args[0] = argv[0];
+	    for (i = 1; i < 255; i++)
+		args[i] = enif_make_int(env, i);
+	    return enif_schedule_nif(env, "call_dirty_nif_exception", ERL_NIF_DIRTY_JOB_CPU_BOUND,
+				     call_dirty_nif_exception, 255, args);
+	} else {
+	    return enif_raise_exception(env, argv[0]);
+	}
     }
     case 2: {
         int return_badarg_directly;
@@ -1657,20 +1662,32 @@ static ERL_NIF_TERM call_dirty_nif_zero_args(ErlNifEnv* env, int argc, const ERL
 #endif
 
 /*
- * Call enif_make_badarg, but don't return its return value. Instead,
- * return ok.  Result should still be a badarg exception for the erlang
- * caller.
+ * If argv[0] is the integer 0, call enif_make_badarg, but don't return its
+ * return value. Instead, return ok.  Result should still be a badarg
+ * exception for the erlang caller.
+ *
+ * For any other value of argv[0], use it as an exception term and return
+ * the exception.
  */
 static ERL_NIF_TERM call_nif_exception(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 {
     ERL_NIF_TERM exc_term;
     ERL_NIF_TERM badarg_atom = enif_make_atom(env, "badarg");
-
-    /* ignore return value */ enif_make_badarg(env);
-    assert(enif_has_pending_exception(env, NULL));
-    assert(enif_has_pending_exception(env, &exc_term));
-    assert(enif_is_identical(badarg_atom, exc_term));
-    return enif_make_atom(env, "ok");
+    int arg;
+
+    if (enif_get_int(env, argv[0], &arg) && arg == 0) {
+	/* ignore return value */ enif_make_badarg(env);
+	assert(enif_has_pending_exception(env, NULL));
+	assert(enif_has_pending_exception(env, &exc_term));
+	assert(enif_is_identical(badarg_atom, exc_term));
+	return enif_make_atom(env, "ok");
+    } else {
+	ERL_NIF_TERM exc_retval = enif_raise_exception(env, argv[0]);
+	assert(enif_has_pending_exception(env, NULL));
+	assert(enif_has_pending_exception(env, &exc_term));
+	assert(enif_is_identical(argv[0], exc_term));
+	return exc_retval;
+    }
 }
 
 #if !defined(NAN) || !defined(INFINITY)
@@ -1925,7 +1942,7 @@ static ErlNifFunc nif_funcs[] =
     {"call_dirty_nif_exception", 1, call_dirty_nif_exception, ERL_NIF_DIRTY_JOB_IO_BOUND},
     {"call_dirty_nif_zero_args", 0, call_dirty_nif_zero_args, ERL_NIF_DIRTY_JOB_CPU_BOUND},
 #endif
-    {"call_nif_exception", 0, call_nif_exception},
+    {"call_nif_exception", 1, call_nif_exception},
     {"call_nif_nan_or_inf", 1, call_nif_nan_or_inf},
     {"call_nif_atom_too_long", 1, call_nif_atom_too_long},
     {"is_map_nif", 1, is_map_nif},