Merge branch 'bjorn/multiple-load/OTP-13111'

* bjorn/multiple-load/OTP-13111:
  code: Add functions that can load multiple modules
  Refactor post_beam_load handling
  Simplify and robustify code_server:all_loaded/1
  Update preloaded modules
  Add erl_prim_loader:get_modules/3
  Add has_prepared_code_on_load/1 BIF
  Allow erlang:finish_loading/1 to load more than one module
  beam_load.c: Add a function to check for an on_load function

11 files changed, 347 insertions, 104 deletions

diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index 2777c3d112..dca8b503bf 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -211,6 +211,7 @@ atom dsend
 atom dsend_continue_trap
 atom dunlink
 atom duplicate_bag
+atom duplicated
 atom dupnames
 atom einval
 atom elib_malloc
diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index 1b4c022370..0b47fc3586 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -86,7 +86,7 @@ BIF_RETTYPE code_make_stub_module_3(BIF_ALIST_3)
 	ASSERT(modp->curr.num_breakpoints == 0);
     }
 
-    erts_start_staging_code_ix();
+    erts_start_staging_code_ix(1);
 
     res = erts_make_stub_module(BIF_P, BIF_ARG_1, BIF_ARG_2, BIF_ARG_3);
 
@@ -139,6 +139,25 @@ prepare_loading_2(BIF_ALIST_2)
     BIF_RET(res);
 }
 
+BIF_RETTYPE
+has_prepared_code_on_load_1(BIF_ALIST_1)
+{
+    Eterm res;
+    ProcBin* pb;
+
+    if (!ERTS_TERM_IS_MAGIC_BINARY(BIF_ARG_1)) {
+    error:
+	BIF_ERROR(BIF_P, BADARG);
+    }
+
+    pb = (ProcBin*) binary_val(BIF_ARG_1);
+    res = erts_has_code_on_load(pb->val);
+    if (res == NIL) {
+	goto error;
+    }
+    BIF_RET(res);
+}
+
 struct m {
     Binary* code;
     Eterm module;
@@ -163,14 +182,13 @@ exception_list(Process* p, Eterm tag, struct m* mp, Sint exceptions)
     Eterm* hp = HAlloc(p, 3 + 2*exceptions);
     Eterm res = NIL;
 
-    mp += exceptions - 1;
     while (exceptions > 0) {
 	if (mp->exception) {
 	    res = CONS(hp, mp->module, res);
 	    hp += 2;
 	    exceptions--;
 	}
-	mp--;
+	mp++;
     }
     return TUPLE2(hp, tag, res);
 }
@@ -202,8 +220,12 @@ finish_loading_1(BIF_ALIST_1)
 
     n = erts_list_length(BIF_ARG_1);
     if (n < 0) {
-	ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	goto done;
+    badarg:
+	if (p) {
+	    erts_free(ERTS_ALC_T_LOADER_TMP, p);
+	}
+	erts_release_code_write_permission();
+	BIF_ERROR(BIF_P, BADARG);
     }
     p = erts_alloc(ERTS_ALC_T_LOADER_TMP, n*sizeof(struct m));
 
@@ -218,29 +240,32 @@ finish_loading_1(BIF_ALIST_1)
 	ProcBin* pb;
 
 	if (!ERTS_TERM_IS_MAGIC_BINARY(term)) {
-	    ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	    goto done;
+	    goto badarg;
 	}
 	pb = (ProcBin*) binary_val(term);
 	p[i].code = pb->val;
 	p[i].module = erts_module_for_prepared_code(p[i].code);
 	if (p[i].module == NIL) {
-	    ERTS_BIF_PREP_ERROR(res, BIF_P, BADARG);
-	    goto done;
+	    goto badarg;
 	}
 	BIF_ARG_1 = CDR(cons);
     }
 
     /*
      * Since we cannot handle atomic loading of a group of modules
-     * if one or more of them uses on_load, we will only allow one
-     * element in the list. This limitation is intended to be
-     * lifted in the future.
+     * if one or more of them uses on_load, we will only allow
+     * more than one element in the list if none of the modules
+     * have an on_load function.
      */
 
     if (n > 1) {
-	ERTS_BIF_PREP_ERROR(res, BIF_P, SYSTEM_LIMIT);
-	goto done;
+	for (i = 0; i < n; i++) {
+	    if (erts_has_code_on_load(p[i].code) == am_true) {
+		erts_free(ERTS_ALC_T_LOADER_TMP, p);
+		erts_release_code_write_permission();
+		BIF_ERROR(BIF_P, SYSTEM_LIMIT);
+	    }
+	}
     }
 
     /*
@@ -252,11 +277,27 @@ finish_loading_1(BIF_ALIST_1)
      */
 
     res = am_ok;
-    erts_start_staging_code_ix();
+    erts_start_staging_code_ix(n);
 
     for (i = 0; i < n; i++) {
 	p[i].modp = erts_put_module(p[i].module);
+	p[i].modp->seen = 0;
     }
+
+    exceptions = 0;
+    for (i = 0; i < n; i++) {
+	p[i].exception = 0;
+	if (p[i].modp->seen) {
+	    p[i].exception = 1;
+	    exceptions++;
+	}
+	p[i].modp->seen = 1;
+    }
+    if (exceptions) {
+	res = exception_list(BIF_P, am_duplicated, p, exceptions);
+	goto done;
+    }
+
     for (i = 0; i < n; i++) {
 	if (p[i].modp->curr.num_breakpoints > 0 ||
 	    p[i].modp->curr.num_traced_exports > 0 ||
@@ -492,7 +533,7 @@ BIF_RETTYPE delete_module_1(BIF_ALIST_1)
     }
 
     {
-	erts_start_staging_code_ix();
+	erts_start_staging_code_ix(0);
 	code_ix = erts_staging_code_ix();
 	modp = erts_get_module(BIF_ARG_1, code_ix);
 	if (!modp) {
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 1511a4f935..f115df935f 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -888,6 +888,23 @@ erts_module_for_prepared_code(Binary* magic)
     }
 }
 
+/*
+ * Return a non-zero value if the module has an on_load function,
+ * or 0 if it does not.
+ */
+
+Eterm
+erts_has_code_on_load(Binary* magic)
+{
+    LoaderState* stp;
+
+    if (ERTS_MAGIC_BIN_DESTRUCTOR(magic) != loader_state_dtor) {
+	return NIL;
+    }
+    stp = ERTS_MAGIC_BIN_DATA(magic);
+    return stp->on_load ? am_true : am_false;
+}
+
 static void
 free_loader_state(Binary* magic)
 {
diff --git a/erts/emulator/beam/beam_ranges.c b/erts/emulator/beam/beam_ranges.c
index 5a2b66727a..54c337ee72 100644
--- a/erts/emulator/beam/beam_ranges.c
+++ b/erts/emulator/beam/beam_ranges.c
@@ -53,6 +53,7 @@ struct ranges {
 };
 static struct ranges r[ERTS_NUM_CODE_IX];
 static erts_smp_atomic_t mem_used;
+static Range* write_ptr;
 
 #ifdef HARD_DEBUG
 static void check_consistency(struct ranges* p)
@@ -72,6 +73,17 @@ static void check_consistency(struct ranges* p)
 #  define CHECK(r)
 #endif /* HARD_DEBUG */
 
+static int
+rangecompare(Range* a, Range* b)
+{
+    if (a->start < b->start) {
+	return -1;
+    } else if (a->start == b->start) {
+	return 0;
+    } else {
+	return 1;
+    }
+}
 
 void
 erts_init_ranges(void)
@@ -88,45 +100,70 @@ erts_init_ranges(void)
 }
 
 void
-erts_start_staging_ranges(void)
+erts_start_staging_ranges(int num_new)
 {
+    ErtsCodeIndex src = erts_active_code_ix();
     ErtsCodeIndex dst = erts_staging_code_ix();
+    Sint need;
 
     if (r[dst].modules) {
 	erts_smp_atomic_add_nob(&mem_used, -r[dst].allocated);
 	erts_free(ERTS_ALC_T_MODULE_REFS, r[dst].modules);
-	r[dst].modules = NULL;
     }
+
+    need = r[dst].allocated = r[src].n + num_new;
+    erts_smp_atomic_add_nob(&mem_used, need);
+    write_ptr = erts_alloc(ERTS_ALC_T_MODULE_REFS,
+			   need * sizeof(Range));
+    r[dst].modules = write_ptr;
 }
 
 void
 erts_end_staging_ranges(int commit)
 {
-    ErtsCodeIndex dst = erts_staging_code_ix();
-
-    if (commit && r[dst].modules == NULL) {
+    if (commit) {
 	Sint i;
-	Sint n;
-
-	/* No modules added, just clone src and remove purged code. */
 	ErtsCodeIndex src = erts_active_code_ix();
+	ErtsCodeIndex dst = erts_staging_code_ix();
+	Range* mp;
+	Sint num_inserted;
 
-	erts_smp_atomic_add_nob(&mem_used, r[src].n);
-	r[dst].modules = erts_alloc(ERTS_ALC_T_MODULE_REFS,
-				    r[src].n * sizeof(Range));
-	r[dst].allocated = r[src].n;
-	n = 0;
+	mp = r[dst].modules;
+	num_inserted = write_ptr - mp;
 	for (i = 0; i < r[src].n; i++) {
 	    Range* rp = r[src].modules+i;
 	    if (rp->start < RANGE_END(rp)) {
 		/* Only insert a module that has not been purged. */
-		r[dst].modules[n] = *rp;
-		n++;
+		write_ptr->start = rp->start;
+		erts_smp_atomic_init_nob(&write_ptr->end,
+					 (erts_aint_t)(RANGE_END(rp)));
+		write_ptr++;
+	    }
+	}
+
+	/*
+	 * There are num_inserted new range entries (unsorted) at the
+	 * beginning of the modules array, followed by the old entries
+	 * (sorted). We must now sort the entire array.
+	 */
+
+	r[dst].n = write_ptr - mp;
+	if (num_inserted > 1) {
+	    qsort(mp, r[dst].n, sizeof(Range),
+		  (int (*)(const void *, const void *)) rangecompare);
+	} else if (num_inserted == 1) {
+	    /* Sift the new range into place. This is faster than qsort(). */
+	    Range t = mp[0];
+	    for (i = 0; i < r[dst].n-1 && t.start > mp[i+1].start; i++) {
+		mp[i] = mp[i+1];
 	    }
+	    mp[i] = t;
 	}
-	r[dst].n = n;
+	r[dst].modules = mp;
+	CHECK(&r[dst]);
 	erts_smp_atomic_set_nob(&r[dst].mid,
-				(erts_aint_t) (r[dst].modules + n / 2));
+				(erts_aint_t) (r[dst].modules +
+					       r[dst].n / 2));
     }
 }
 
@@ -135,82 +172,29 @@ erts_update_ranges(BeamInstr* code, Uint size)
 {
     ErtsCodeIndex dst = erts_staging_code_ix();
     ErtsCodeIndex src = erts_active_code_ix();
-    Sint i;
-    Sint n;
-    Sint need;
 
     if (src == dst) {
 	ASSERT(!erts_initialized);
 
 	/*
-	 * During start-up of system, the indices are the same.
-	 * Handle this by faking a source area.
+	 * During start-up of system, the indices are the same
+	 * and erts_start_staging_ranges() has not been called.
 	 */
-	src = (src+1) % ERTS_NUM_CODE_IX;
-	if (r[src].modules) {
-	    erts_smp_atomic_add_nob(&mem_used, -r[src].allocated);
-	    erts_free(ERTS_ALC_T_MODULE_REFS, r[src].modules);
+	if (r[dst].modules == NULL) {
+	    Sint need = 128;
+	    erts_smp_atomic_add_nob(&mem_used, need);
+	    r[dst].modules = erts_alloc(ERTS_ALC_T_MODULE_REFS,
+					need * sizeof(Range));
+	    r[dst].allocated = need;
+	    write_ptr = r[dst].modules;
 	}
-	r[src] = r[dst];
-	r[dst].modules = 0;
     }
 
-    CHECK(&r[src]);
-
-    ASSERT(r[dst].modules == NULL);
-    need = r[dst].allocated = r[src].n + 1;
-    erts_smp_atomic_add_nob(&mem_used, need);
-    r[dst].modules = (Range *) erts_alloc(ERTS_ALC_T_MODULE_REFS,
-					  need * sizeof(Range));
-    n = 0;
-    for (i = 0; i < r[src].n; i++) {
-	Range* rp = r[src].modules+i;
-	if (code < rp->start) {
-	    r[dst].modules[n].start = code;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(((byte *)code) + size));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < code);
-	    n++;
-	    break;
-	}
-	if (rp->start < RANGE_END(rp)) {
-	    /* Only insert a module that has not been purged. */
-	    r[dst].modules[n].start = rp->start;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(RANGE_END(rp)));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < rp->start);
-	    n++;
-	}
-    }
-
-    while (i < r[src].n) {
-	Range* rp = r[src].modules+i;
-	if (rp->start < RANGE_END(rp)) {
-	    /* Only insert a module that has not been purged. */
-	    r[dst].modules[n].start = rp->start;
-	    erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				     (erts_aint_t)(RANGE_END(rp)));
-	    ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < rp->start);
-	    n++;
-	}
-	i++;
-    }
-
-    if (n == 0 || code > r[dst].modules[n-1].start) {
-	r[dst].modules[n].start = code;
-	erts_smp_atomic_init_nob(&r[dst].modules[n].end,
-				 (erts_aint_t)(((byte *)code) + size));
-	ASSERT(!n || RANGE_END(&r[dst].modules[n-1]) < code);
-	n++;
-    }
-
-    ASSERT(n <= r[src].n+1);
-    r[dst].n = n;
-    erts_smp_atomic_set_nob(&r[dst].mid,
-			    (erts_aint_t) (r[dst].modules + n / 2));
-
-    CHECK(&r[dst]);
-    CHECK(&r[src]);
+    ASSERT(r[dst].modules);
+    write_ptr->start = code;
+    erts_smp_atomic_init_nob(&(write_ptr->end),
+			     (erts_aint_t)(((byte *)code) + size));
+    write_ptr++;
 }
 
 void
diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab
index 77d3d95673..a6670c10e8 100644
--- a/erts/emulator/beam/bif.tab
+++ b/erts/emulator/beam/bif.tab
@@ -651,6 +651,7 @@ bif binary:split/2
 bif binary:split/3
 bif erts_debug:size_shared/1
 bif erts_debug:copy_shared/1
+bif erlang:has_prepared_code_on_load/1
 
 #
 # Obsolete
diff --git a/erts/emulator/beam/code_ix.c b/erts/emulator/beam/code_ix.c
index 209d008d18..1b0968c55c 100644
--- a/erts/emulator/beam/code_ix.c
+++ b/erts/emulator/beam/code_ix.c
@@ -65,12 +65,12 @@ void erts_code_ix_init(void)
     CIX_TRACE("init");
 }
 
-void erts_start_staging_code_ix(void)
+void erts_start_staging_code_ix(int num_new)
 {
     beam_catches_start_staging();
     export_start_staging();
     module_start_staging();
-    erts_start_staging_ranges();
+    erts_start_staging_ranges(num_new);
     CIX_TRACE("start");
 }
 
diff --git a/erts/emulator/beam/code_ix.h b/erts/emulator/beam/code_ix.h
index 5f00b409ef..7a66211a5b 100644
--- a/erts/emulator/beam/code_ix.h
+++ b/erts/emulator/beam/code_ix.h
@@ -100,7 +100,7 @@ void erts_release_code_write_permission(void);
  * Must be followed by calls to either "end" and "commit" or "abort" before
  * code write permission can be released.
  */
-void erts_start_staging_code_ix(void);
+void erts_start_staging_code_ix(int num_new);
 
 /* End the staging.
  * Preceded by "start" and must be followed by "commit".
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 2a8bdb6ee3..956efa5e36 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -1008,6 +1008,7 @@ typedef struct {
 
 Binary* erts_alloc_loader_state(void);
 Eterm erts_module_for_prepared_code(Binary* magic);
+Eterm erts_has_code_on_load(Binary* magic);
 Eterm erts_prepare_loading(Binary* loader_state,  Process *c_p,
 			   Eterm group_leader, Eterm* modp,
 			   byte* code, Uint size);
@@ -1026,7 +1027,7 @@ Eterm erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info);
 
 /* beam_ranges.c */
 void erts_init_ranges(void);
-void erts_start_staging_ranges(void);
+void erts_start_staging_ranges(int num_new);
 void erts_end_staging_ranges(int commit);
 void erts_update_ranges(BeamInstr* code, Uint size);
 void erts_remove_from_ranges(BeamInstr* code);
diff --git a/erts/emulator/beam/module.h b/erts/emulator/beam/module.h
index e66d628ca9..b7468b0926 100644
--- a/erts/emulator/beam/module.h
+++ b/erts/emulator/beam/module.h
@@ -37,6 +37,7 @@ struct erl_module_instance {
 typedef struct erl_module {
     IndexSlot slot;		/* Must be located at top of struct! */
     int module;			/* Atom index for module (not tagged). */
+    int seen;			/* Used by finish_loading() */
 
     struct erl_module_instance curr;
     struct erl_module_instance old; /* protected by "old_code" rwlock */
diff --git a/erts/emulator/test/Makefile b/erts/emulator/test/Makefile
index 987a655c3d..318db4b45e 100644
--- a/erts/emulator/test/Makefile
+++ b/erts/emulator/test/Makefile
@@ -74,6 +74,7 @@ MODULES= \
 	match_spec_SUITE \
 	module_info_SUITE \
 	monitor_SUITE \
+	multi_load_SUITE \
 	nested_SUITE \
 	nif_SUITE \
 	node_container_SUITE \
diff --git a/erts/emulator/test/multi_load_SUITE.erl b/erts/emulator/test/multi_load_SUITE.erl
new file mode 100644
index 0000000000..784b239116
--- /dev/null
+++ b/erts/emulator/test/multi_load_SUITE.erl
@@ -0,0 +1,196 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1999-2012. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(multi_load_SUITE).
+-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1,
+	 init_per_group/2,end_per_group/2,
+	 many/1,on_load/1,errors/1]).
+
+-include_lib("common_test/include/ct.hrl").
+
+suite() -> [{ct_hooks,[ts_install_cth]}].
+
+all() ->
+    [many,on_load,errors].
+
+groups() ->
+    [].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_GroupName, Config) ->
+    Config.
+
+end_per_group(_GroupName, Config) ->
+    Config.
+
+many(_Config) ->
+    Ms = make_modules(100, fun many_module/1),
+
+    io:put_chars("Light load\n"
+		 "=========="),
+    many_measure(Ms),
+
+    _ = [spawn_link(fun many_worker/0) || _ <- lists:seq(1, 8)],
+    erlang:yield(),
+    io:put_chars("Heavy load\n"
+		 "=========="),
+    many_measure(Ms),
+
+    ok.
+
+many_module(M) ->
+    ["-module("++M++").",
+     "-compile(export_all).",
+     "f1() -> ok.",
+     "f2() -> ok.",
+     "f3() -> ok.",
+     "f4() -> ok."].
+
+many_measure(Ms) ->
+    many_purge(Ms),
+    MsPrep1 = prepare_modules(Ms),
+    Us1 = ms(fun() -> many_load_seq(MsPrep1) end),
+    many_try_call(Ms),
+    many_purge(Ms),
+    MsPrep2 = prepare_modules(Ms),
+    Us2 = ms(fun() -> many_load_par(MsPrep2) end),
+    many_try_call(Ms),
+    io:format("# modules:  ~9w\n"
+	      "Sequential: ~9w µs\n"
+	      "Parallel:   ~9w µs\n"
+	      "Ratio:      ~9w\n",
+	      [length(Ms),Us1,Us2,round(Us1/Us2)]),
+    ok.
+
+many_load_seq(Ms) ->
+    [erlang:finish_loading([M]) || M <- Ms],
+    ok.
+
+many_load_par(Ms) ->
+    erlang:finish_loading(Ms).
+
+many_purge(Ms) ->
+    _ = [catch erlang:purge_module(M) || {M,_} <- Ms],
+    ok.
+
+many_try_call(Ms) ->
+    _ = [begin
+	     ok = M:f1(),
+	     ok = M:f2(),
+	     ok = M:f3(),
+	     ok = M:f4()
+	 end || {M,_} <- Ms],
+    ok.
+
+many_worker() ->
+    many_worker(lists:seq(1, 100)).
+
+many_worker(L) ->
+    N0 = length(L),
+    N1 = N0 * N0 * N0,
+    N2 = N1 div (N0 * N0),
+    N3 = N2 + 10,
+    _ = N3 - 10,
+    many_worker(L).
+
+
+on_load(_Config) ->
+    On = make_modules(2, fun on_load_module/1),
+    OnPrep = prepare_modules(On),
+    {'EXIT',{system_limit,_}} = (catch erlang:finish_loading(OnPrep)),
+
+    Normal = make_modules(1, fun on_load_normal/1),
+    Mixed = Normal ++ tl(On),
+    MixedPrep = prepare_modules(Mixed),
+    {'EXIT',{system_limit,_}} = (catch erlang:finish_loading(MixedPrep)),
+
+    [false,true] = [erlang:has_prepared_code_on_load(Code) ||
+		       Code <- MixedPrep],
+    {'EXIT',{badarg,_}} = (catch erlang:has_prepared_code_on_load(<<1,2,3>>)),
+    Magic = ets:match_spec_compile([{'_',[true],['$_']}]),
+    {'EXIT',{badarg,_}} = (catch erlang:has_prepared_code_on_load(Magic)),
+
+    SingleOnPrep = tl(OnPrep),
+    {on_load,[OnLoadMod]} = erlang:finish_loading(SingleOnPrep),
+    ok = erlang:call_on_load_function(OnLoadMod),
+
+    ok.
+
+on_load_module(M) ->
+    ["-module("++M++").",
+     "-on_load(f/0).",
+     "f() -> ok."].
+
+on_load_normal(M) ->
+    ["-module("++M++")."].
+
+
+errors(_Config) ->
+    finish_loading_badarg(x),
+    finish_loading_badarg([x|y]),
+    finish_loading_badarg([x]),
+    finish_loading_badarg([<<>>]),
+
+    Mods = make_modules(2, fun errors_module/1),
+    Ms = lists:sort([M || {M,_} <- Mods]),
+    Prep = prepare_modules(Mods),
+    {duplicated,Dups} = erlang:finish_loading(Prep ++ Prep),
+    Ms = lists:sort(Dups),
+    ok.
+
+finish_loading_badarg(Arg) ->
+    {'EXIT',{badarg,[{erlang,finish_loading,[Arg],_}|_]}} =
+	(catch erlang:finish_loading(Arg)).
+
+errors_module(M) ->
+    ["-module("++M++").",
+     "-export([f/0]).",
+     "f() -> ok."].
+
+%%%
+%%% Common utilities
+%%%
+
+ms(Fun) ->
+    {Ms,ok} = timer:tc(Fun),
+    Ms.
+
+make_modules(0, _) ->
+    [];
+make_modules(N, Fun) ->
+    U = erlang:unique_integer([positive]),
+    M0 = "m__" ++ integer_to_list(N) ++ "_" ++ integer_to_list(U),
+    Contents = Fun(M0),
+    Forms = [make_form(S) || S <- Contents],
+    {ok,M,Code} = compile:forms(Forms),
+    [{M,Code}|make_modules(N-1, Fun)].
+
+make_form(S) ->
+    {ok,Toks,_} = erl_scan:string(S),
+    {ok,Form} = erl_parse:parse_form(Toks),
+    Form.
+
+prepare_modules(Ms) ->
+    [erlang:prepare_loading(M, Code) || {M,Code} <- Ms].