FIXED: Handling of the Prolog flag compile_meta_arguments.

boot/expand.pl

@@ -1421,10 +1421,12 @@
     sub_atom(Name, 0, _, _, '__aux_meta_call_').
 
 compile_meta(CallIn, CallOut, M, Term, (CallOut :- Body)) :-
-    term_variables(Term, AllVars),
+    replace_subterm(CallIn, true, Term, Term2),
+    term_variables(Term2, AllVars),
     term_variables(CallIn, InVars),
     intersection_eq(InVars, AllVars, HeadVars),
-    variant_sha1(CallIn+HeadVars, Hash),
+    copy_term_nat(CallIn+HeadVars, NAT),
+    variant_sha1(NAT, Hash),
     atom_concat('__aux_meta_call_', Hash, AuxName),
     expand_goal(CallIn, _Pos0, Body, _Pos, M, [], (CallOut:-CallIn), []),
     length(HeadVars, Arity),
@@ -1434,6 +1436,34 @@
     ),
     CallOut =.. [AuxName|HeadArgs].
 
+%!  replace_subterm(From, To, TermIn, TermOut)
+%
+%   Replace instances (==/2) of From inside TermIn by To.
+
+replace_subterm(From, To, TermIn, TermOut) :-
+    From == TermIn,
+    !,
+    TermOut = To.
+replace_subterm(From, To, TermIn, TermOut) :-
+    compound(TermIn),
+    compound_name_arity(TermIn, Name, Arity),
+    Arity > 0,
+    !,
+    compound_name_arity(TermOut, Name, Arity),
+    replace_subterm_compound(1, Arity, From, To, TermIn, TermOut).
+replace_subterm(_, _, Term, Term).
+
+replace_subterm_compound(I, Arity, From, To, TermIn, TermOut) :-
+    I =< Arity,
+    !,
+    arg(I, TermIn, A1),
+    arg(I, TermOut, A2),
+    replace_subterm(From, To, A1, A2),
+    I2 is I+1,
+    replace_subterm_compound(I2, Arity, From, To, TermIn, TermOut).
+replace_subterm_compound(_I, _Arity, _From, _To, _TermIn, _TermOut).
+
+
 %!  intersection_eq(+Small, +Big, -Shared) is det.
 %
 %   Shared are the variables in Small that   also appear in Big. The

man/overview.doc

@@ -1265,29 +1265,28 @@ print_message/2.
     \end{itemize}
 
     \prologflagitem{compile_meta_arguments}{atom}{rw}
-Experimental flag that controls compilation of arguments passed to
-meta-calls marked `0' or `\chr{^}' (see meta_predicate/1). Supported
-values are:
+This flag controls compilation of arguments passed to meta-calls marked
+`0' or `\chr{^}' (see meta_predicate/1). Supported values are:
 
 \begin{description}
     \termitem{false}{}
-(default).  Meta-arguments are passed verbatim.
+(default). Meta-arguments are passed verbatim. If the argument is a
+control structure ((A,B), (A;B), (A->B;C), etc.) it is compile to an
+temporary clause allocated on the environment stack when the
+meta-predicate is called.
+
     \termitem{control}{}
-Compile meta-arguments that contain control structures ((A,B), (A;B),
-(A->B;C), etc.).  If not compiled at compile time, such arguments are
-compiled to a temporary clause before execution.  Using this option
-enhances performance of processing complex meta-goals that are known
-at compile time.
-    \termitem{true}{}
-Also compile references to normal user predicates. This harms
-performance (a little), but enhances the power of poor-mens consistency
-check used by make/0 and implemented by list_undefined/0.
+Compile meta-arguments that contain control structures to an auxiliary
+predicate.  This generally improves performance as well as the debugging
+experience.
+
     \termitem{always}{}
-Always create an intermediate clause, even for system predicates. This
-prepares for replacing the normal head of the generated predicate with
-a special reference (similar to database references as used by, e.g.,
-assert/2) that provides direct access to the executable code, thus
-avoiding runtime lookup of predicates for meta-calling.
+Always create an intermediate clause, even for system
+predicates.\footnote{This may be used in the future for
+replacing the normal head of the generated predicate with a special
+reference (similar to database references as used by, e.g., assert/2)
+that provides direct access to the executable code, thus avoiding
+runtime lookup of predicates for meta-calling.}
 \end{description}
 
     \prologflagitem{compiled_at}{atom}{r}