Reinstate tuple calls support in the beam emulator

This reverts commit f2b332186a for beam_emu.c only, to enable
an upgrade path for existing beam code compiled under OTP 20 with
parameterized modules.

1 files changed, 33 insertions, 4 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index e909a0b4da..aa6e7d3de2 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -2210,6 +2210,7 @@ apply(Process* p, Eterm* reg, BeamInstr *I, Uint stack_offset)
     Eterm module = reg[0];
     Eterm function = reg[1];
     Eterm args = reg[2];
+    Eterm this;
 
     /*
      * Check the arguments which should be of the form apply(Module,
@@ -2232,8 +2233,20 @@ apply(Process* p, Eterm* reg, BeamInstr *I, Uint stack_offset)
 
     while (1) {
 	Eterm m, f, a;
-
-	if (is_not_atom(module)) goto error;
+	/* The module argument may be either an atom or an abstract module
+	 * (currently implemented using tuples, but this might change).
+	 */
+	this = THE_NON_VALUE;
+	if (is_not_atom(module)) {
+	    Eterm* tp;
+
+	    if (is_not_tuple(module)) goto error;
+	    tp = tuple_val(module);
+	    if (arityval(tp[0]) < 1) goto error;
+	    this = module;
+	    module = tp[1];
+	    if (is_not_atom(module)) goto error;
+	}
 
 	if (module != am_erlang || function != am_apply)
 	    break;
@@ -2268,7 +2281,9 @@ apply(Process* p, Eterm* reg, BeamInstr *I, Uint stack_offset)
     }
     /*
      * Walk down the 3rd parameter of apply (the argument list) and copy
-     * the parameters to the x registers (reg[]).
+     * the parameters to the x registers (reg[]). If the module argument
+     * was an abstract module, add 1 to the function arity and put the
+     * module argument in the n+1st x register as a THIS reference.
      */
 
     tmp = args;
@@ -2285,6 +2300,9 @@ apply(Process* p, Eterm* reg, BeamInstr *I, Uint stack_offset)
     if (is_not_nil(tmp)) {	/* Must be well-formed list */
 	goto error;
     }
+    if (this != THE_NON_VALUE) {
+        reg[arity++] = this;
+    }
 
     /*
      * Get the index into the export table, or failing that the export
@@ -2323,7 +2341,18 @@ fixed_apply(Process* p, Eterm* reg, Uint arity,
 	return 0;
     }
 
-    if (is_not_atom(module)) goto error;
+    /* The module argument may be either an atom or an abstract module
+     * (currently implemented using tuples, but this might change).
+     */
+    if (is_not_atom(module)) {
+	Eterm* tp;
+        if (is_not_tuple(module)) goto error;
+        tp = tuple_val(module);
+        if (arityval(tp[0]) < 1) goto error;
+        module = tp[1];
+        if (is_not_atom(module)) goto error;
+        ++arity;
+    }
 
     /* Handle apply of apply/3... */
     if (module == am_erlang && function == am_apply && arity == 3) {