Reimplement module functions

Instead of a lambda, create a new type containing all data required to
call the function, and support it in the evaluator.  Because this type
now also needs to store the function documentation, it is too big for
Lisp_Misc; use a pseudovector instead.  That also has the nice benefit
that we don't have to add special support to the garbage collector.

Since the new type is user-visible, give it a predicate.

Now we can easily support 'help-function-args' and 'func-arity'; add
unit tests for these.

* src/lisp.h (allocate_module_function, MODULE_FUNCTIONP)
(XMODULE_FUNCTION): New pseudovector type 'module function'.

* src/eval.c (FUNCTIONP): Also treat module functions as functions.
(funcall_lambda, Ffuncall, eval_sub): Add support for calling module
functions.
(Ffunc_arity): Add support for detecting the arity of module
functions.

* src/emacs-module.c (module_make_function): Adapt to new structure.
Return module function object directly instead of wrapping it in a
lambda; remove FIXME.
(funcall_module): New function to call module functions.  Replaces
`internal--module-call' and is called directly from eval.c.
(syms_of_module): Remove internal helper function, which is no longer
needed.
(module_function_arity): New helper function.

* src/data.c (Ftype_of): Adapt to new implementation.
(Fmodule_function_p, syms_of_data): New user-visible function.  Now
that module functions are first-class objects, they deserve a
predicate.  Define it even if not compiled with --enable-modules so
that Lisp code doesn't have to check for the function's existence.

* src/doc.c (Fdocumentation): Support module functions.

* src/print.c (print_object): Adapt to new implementation.

* src/alloc.c (mark_object): Specialized garbage collector support is
no longer needed.

* lisp/help.el (help-function-arglist): Support module functions.
While there, simplify the arity calculation by using `func-arity',
which does the right thing for all kinds of functions.

* test/data/emacs-module/mod-test.c: Amend docstring so we can test
the argument list.

* test/src/emacs-module-tests.el (mod-test-sum-docstring): Adapt to
new docstring.
(mod-test-non-local-exit-signal-test): Because `internal--module-call'
is gone, the backtrace has changed and no longer leaks the
implementation.
(module--func-arity): New test for `func-arity'.
(module--help-function-arglist): New test for `help-function-arglist'.

7 files changed, 111 insertions, 85 deletions

diff --git a/src/alloc.c b/src/alloc.c
index faa14eebb36..b473ebd7ded 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3942,13 +3942,6 @@ make_user_ptr (void (*finalizer) (void *), void *p)
   uptr->p = p;
   return obj;
 }
-
-/* Create a new module function environment object.  */
-Lisp_Object
-make_module_function (void)
-{
-  return allocate_misc (Lisp_Misc_Module_Function);
-}
 #endif
 
 static void
@@ -6640,7 +6633,6 @@ mark_object (Lisp_Object arg)
 
 #ifdef HAVE_MODULES
         case Lisp_Misc_User_Ptr:
-        case Lisp_Misc_Module_Function:
           XMISCANY (obj)->gcmarkbit = true;
           break;
 #endif
diff --git a/src/data.c b/src/data.c
index 4242b90e628..25859105ee0 100644
--- a/src/data.c
+++ b/src/data.c
@@ -233,8 +233,6 @@ for example, (type-of 1) returns `integer'.  */)
         case Lisp_Misc_Finalizer:
           return Qfinalizer;
 #ifdef HAVE_MODULES
-        case Lisp_Misc_Module_Function:
-          return Qmodule_function;
         case Lisp_Misc_User_Ptr:
           return Quser_ptr;
 #endif
@@ -278,6 +276,8 @@ for example, (type-of 1) returns `integer'.  */)
             else
               return t;
           }
+        case PVEC_MODULE_FUNCTION:
+          return Qmodule_function;
         /* "Impossible" cases.  */
         case PVEC_XWIDGET:
         case PVEC_OTHER:
@@ -494,6 +494,14 @@ DEFUN ("byte-code-function-p", Fbyte_code_function_p, Sbyte_code_function_p,
   return Qnil;
 }
 
+DEFUN ("module-function-p", Fmodule_function_p, Smodule_function_p, 1, 1, NULL,
+       doc: /* Return t if OBJECT is a function loaded from a dynamic module.  */
+       attributes: const)
+  (Lisp_Object object)
+{
+  return MODULE_FUNCTIONP (object) ? Qt : Qnil;
+}
+
 DEFUN ("char-or-string-p", Fchar_or_string_p, Schar_or_string_p, 1, 1, 0,
        doc: /* Return t if OBJECT is a character or a string.  */
        attributes: const)
@@ -3793,6 +3801,7 @@ syms_of_data (void)
   defsubr (&Smarkerp);
   defsubr (&Ssubrp);
   defsubr (&Sbyte_code_function_p);
+  defsubr (&Smodule_function_p);
   defsubr (&Schar_or_string_p);
   defsubr (&Sthreadp);
   defsubr (&Smutexp);
diff --git a/src/doc.c b/src/doc.c
index dd674e3bc05..345e18b9186 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -340,6 +340,8 @@ string is passed through `substitute-command-keys'.  */)
     fun = XCDR (fun);
   if (SUBRP (fun))
     doc = make_number (XSUBR (fun)->doc);
+  else if (MODULE_FUNCTIONP (fun))
+    doc = XMODULE_FUNCTION (fun)->documentation;
   else if (COMPILEDP (fun))
     {
       if (PVSIZE (fun) <= COMPILED_DOC_STRING)
diff --git a/src/emacs-module.c b/src/emacs-module.c
index 0bc1b6c384b..99be4a748ee 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -362,30 +362,24 @@ module_make_function (emacs_env *env, ptrdiff_t min_arity, ptrdiff_t max_arity,
              : min_arity <= max_arity)))
     xsignal2 (Qinvalid_arity, make_number (min_arity), make_number (max_arity));
 
-  Lisp_Object envobj = make_module_function ();
-  struct Lisp_Module_Function *envptr = XMODULE_FUNCTION (envobj);
+  struct Lisp_Module_Function *envptr = allocate_module_function ();
   envptr->min_arity = min_arity;
   envptr->max_arity = max_arity;
   envptr->subr = subr;
   envptr->data = data;
 
-  Lisp_Object doc = Qnil;
   if (documentation)
     {
       AUTO_STRING (unibyte_doc, documentation);
-      doc = code_convert_string_norecord (unibyte_doc, Qutf_8, false);
+      envptr->documentation =
+        code_convert_string_norecord (unibyte_doc, Qutf_8, false);
     }
 
-  /* FIXME: Use a bytecompiled object, or even better a subr.  */
-  Lisp_Object ret = list4 (Qlambda,
-                           list2 (Qand_rest, Qargs),
-                           doc,
-                           list4 (Qapply,
-                                  list2 (Qfunction, Qinternal__module_call),
-                                  envobj,
-                                  Qargs));
+  Lisp_Object envobj;
+  XSET_MODULE_FUNCTION (envobj, envptr);
+  eassert (MODULE_FUNCTIONP (envobj));
 
-  return lisp_to_value (ret);
+  return lisp_to_value (envobj);
 }
 
 static emacs_value
@@ -648,17 +642,11 @@ DEFUN ("module-load", Fmodule_load, Smodule_load, 1, 1, 0,
   return Qt;
 }
 
-DEFUN ("internal--module-call", Finternal_module_call, Sinternal_module_call, 1, MANY, 0,
-       doc: /* Internal function to call a module function.
-ENVOBJ is a save pointer to a module_fun_env structure.
-ARGLIST is a list of arguments passed to SUBRPTR.
-usage: (module-call ENVOBJ &rest ARGLIST)   */)
-  (ptrdiff_t nargs, Lisp_Object *arglist)
+Lisp_Object
+funcall_module (const struct Lisp_Module_Function *const envptr,
+                ptrdiff_t nargs, Lisp_Object *arglist)
 {
-  Lisp_Object envobj = arglist[0];
-  CHECK_TYPE (MODULE_FUNCTIONP (envobj), Qmodule_function_p, envobj);
-  struct Lisp_Module_Function *envptr = XMODULE_FUNCTION (envobj);
-  EMACS_INT len = nargs - 1;
+  EMACS_INT len = nargs;
   eassume (0 <= envptr->min_arity);
   if (! (envptr->min_arity <= len
          && len <= (envptr->max_arity < 0 ? PTRDIFF_MAX : envptr->max_arity)))
@@ -672,12 +660,12 @@ usage: (module-call ENVOBJ &rest ARGLIST)   */)
   USE_SAFE_ALLOCA;
   emacs_value *args;
   if (plain_values)
-    args = (emacs_value *) arglist + 1;
+    args = (emacs_value *) arglist;
   else
     {
       args = SAFE_ALLOCA (len * sizeof *args);
       for (ptrdiff_t i = 0; i < len; i++)
-        args[i] = lisp_to_value (arglist[i + 1]);
+        args[i] = lisp_to_value (arglist[i]);
     }
 
   emacs_value ret = envptr->subr (&pub, len, args, envptr->data);
@@ -709,6 +697,15 @@ usage: (module-call ENVOBJ &rest ARGLIST)   */)
     }
 }
 
+Lisp_Object
+module_function_arity (const struct Lisp_Module_Function *const function)
+{
+  const short minargs = function->min_arity;
+  const short maxargs = function->max_arity;
+  return Fcons (make_number (minargs),
+                maxargs == MANY ? Qmany : make_number (maxargs));
+}
+
 
 /* Helper functions.  */
 
@@ -1025,7 +1022,4 @@ syms_of_module (void)
   DEFSYM (Qmodule_function_p, "module-function-p");
 
   defsubr (&Smodule_load);
-
-  DEFSYM (Qinternal__module_call, "internal--module-call");
-  defsubr (&Sinternal_module_call);
 }
diff --git a/src/eval.c b/src/eval.c
index 98d25cc4fed..f472efad52e 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2261,7 +2261,7 @@ eval_sub (Lisp_Object form)
             }
         }
     }
-  else if (COMPILEDP (fun))
+  else if (COMPILEDP (fun) || MODULE_FUNCTIONP (fun))
     return apply_lambda (fun, original_args, count);
   else
     {
@@ -2687,7 +2687,7 @@ FUNCTIONP (Lisp_Object object)
 
   if (SUBRP (object))
     return XSUBR (object)->max_args != UNEVALLED;
-  else if (COMPILEDP (object))
+  else if (COMPILEDP (object) || MODULE_FUNCTIONP (object))
     return true;
   else if (CONSP (object))
     {
@@ -2742,7 +2742,7 @@ usage: (funcall FUNCTION &rest ARGUMENTS)  */)
 
   if (SUBRP (fun))
     val = funcall_subr (XSUBR (fun), numargs, args + 1);
-  else if (COMPILEDP (fun))
+  else if (COMPILEDP (fun) || MODULE_FUNCTIONP (fun))
     val = funcall_lambda (fun, numargs, args + 1);
   else
     {
@@ -2892,7 +2892,8 @@ apply_lambda (Lisp_Object fun, Lisp_Object args, ptrdiff_t count)
 
 /* Apply a Lisp function FUN to the NARGS evaluated arguments in ARG_VECTOR
    and return the result of evaluation.
-   FUN must be either a lambda-expression or a compiled-code object.  */
+   FUN must be either a lambda-expression, a compiled-code object,
+   or a module function.  */
 
 static Lisp_Object
 funcall_lambda (Lisp_Object fun, ptrdiff_t nargs,
@@ -2949,6 +2950,10 @@ funcall_lambda (Lisp_Object fun, ptrdiff_t nargs,
         }
       lexenv = Qnil;
     }
+#ifdef HAVE_MODULES
+  else if (MODULE_FUNCTIONP (fun))
+    return funcall_module (XMODULE_FUNCTION (fun), nargs, arg_vector);
+#endif
   else
     emacs_abort ();
 
@@ -3060,6 +3065,10 @@ function with `&rest' args, or `unevalled' for a special form.  */)
     result = Fsubr_arity (function);
   else if (COMPILEDP (function))
     result = lambda_arity (function);
+#ifdef HAVE_MODULES
+  else if (MODULE_FUNCTIONP (function))
+    result = module_function_arity (XMODULE_FUNCTION (function));
+#endif
   else
     {
       if (NILP (function))
diff --git a/src/lisp.h b/src/lisp.h
index de3a548cb6c..ec8a8b1c098 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -464,7 +464,6 @@ enum Lisp_Misc_Type
     Lisp_Misc_Save_Value,
     Lisp_Misc_Finalizer,
 #ifdef HAVE_MODULES
-    Lisp_Misc_Module_Function,
     Lisp_Misc_User_Ptr,
 #endif
     /* Currently floats are not a misc type,
@@ -885,6 +884,7 @@ enum pvec_type
   PVEC_THREAD,
   PVEC_MUTEX,
   PVEC_CONDVAR,
+  PVEC_MODULE_FUNCTION,
 
   /* These should be last, check internal_equal to see why.  */
   PVEC_COMPILED,
@@ -2386,28 +2386,6 @@ struct Lisp_User_Ptr
   void (*finalizer) (void *);
   void *p;
 };
-
-#include "emacs-module.h"
-
-/* Function prototype for the module Lisp functions.  */
-typedef emacs_value (*emacs_subr) (emacs_env *, ptrdiff_t,
-                                   emacs_value [], void *);
-
-/* Function environments.  */
-
-/* A function environment is an auxiliary structure used by
-   `module_make_function' to store information about a module
-   function.  It is stored in a save pointer and retrieved by
-   `internal--module-call'.  Its members correspond to the arguments
-   given to `module_make_function'.  */
-
-struct Lisp_Module_Function
-{
-  struct Lisp_Misc_Any base;
-  ptrdiff_t min_arity, max_arity;
-  emacs_subr subr;
-  void *data;
-};
 #endif
 
 /* A finalizer sentinel.  */
@@ -2460,7 +2438,6 @@ union Lisp_Misc
     struct Lisp_Finalizer u_finalizer;
 #ifdef HAVE_MODULES
     struct Lisp_User_Ptr u_user_ptr;
-    struct Lisp_Module_Function u_module_function;
 #endif
   };
 
@@ -2509,19 +2486,6 @@ XUSER_PTR (Lisp_Object a)
   eassert (USER_PTRP (a));
   return XUNTAG (a, Lisp_Misc);
 }
-
-INLINE bool
-MODULE_FUNCTIONP (Lisp_Object o)
-{
-  return MISCP (o) && XMISCTYPE (o) == Lisp_Misc_Module_Function;
-}
-
-INLINE struct Lisp_Module_Function *
-XMODULE_FUNCTION (Lisp_Object o)
-{
-  eassert (MODULE_FUNCTIONP (o));
-  return XUNTAG (o, Lisp_Misc);
-}
 #endif
 
 
@@ -3923,12 +3887,66 @@ extern void get_backtrace (Lisp_Object array);
 Lisp_Object backtrace_top_function (void);
 extern bool let_shadows_buffer_binding_p (struct Lisp_Symbol *symbol);
 
+#include "emacs-module.h"
+
+/* Function prototype for the module Lisp functions.  */
+typedef emacs_value (*emacs_subr) (emacs_env *, ptrdiff_t,
+                                   emacs_value [], void *);
+
+/* Function environments.  */
+
+/* A function environment is an auxiliary structure used by
+   `module_make_function' to store information about a module
+   function.  It is stored in a pseudovector.  Its members correspond
+   to the arguments given to `module_make_function'.  */
+
+struct Lisp_Module_Function
+{
+  struct vectorlike_header header;
+
+  /* Fields traced by GC; these must come first.  */
+  Lisp_Object documentation;
+
+  /* Fields ignored by GC.  */
+  ptrdiff_t min_arity, max_arity;
+  emacs_subr subr;
+  void *data;
+};
+
+INLINE struct Lisp_Module_Function *
+allocate_module_function (void)
+{
+  return ALLOCATE_PSEUDOVECTOR (struct Lisp_Module_Function,
+                                /* Name of the first field to be
+                                   ignored by GC.  */
+                                min_arity,
+                                PVEC_MODULE_FUNCTION);
+}
+
+INLINE bool
+MODULE_FUNCTIONP (Lisp_Object o)
+{
+  return PSEUDOVECTORP (o, PVEC_MODULE_FUNCTION);
+}
+
+INLINE struct Lisp_Module_Function *
+XMODULE_FUNCTION (Lisp_Object o)
+{
+  eassert (MODULE_FUNCTIONP (o));
+  return XUNTAG (o, Lisp_Vectorlike);
+}
+
+#define XSET_MODULE_FUNCTION(var, ptr)                  \
+  (XSETPSEUDOVECTOR (var, ptr, PVEC_MODULE_FUNCTION))
+
 #ifdef HAVE_MODULES
 /* Defined in alloc.c.  */
 extern Lisp_Object make_user_ptr (void (*finalizer) (void *), void *p);
-extern Lisp_Object make_module_function (void);
 
 /* Defined in emacs-module.c.  */
+extern Lisp_Object funcall_module (const struct Lisp_Module_Function *,
+                                   ptrdiff_t, Lisp_Object *);
+extern Lisp_Object module_function_arity (const struct Lisp_Module_Function *);
 extern Lisp_Object module_format_fun_env (const struct Lisp_Module_Function *);
 extern void syms_of_module (void);
 #endif
diff --git a/src/print.c b/src/print.c
index 7e411a80c88..be2e16a7499 100644
--- a/src/print.c
+++ b/src/print.c
@@ -2051,6 +2051,13 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
         }
         break;
 
+#ifdef HAVE_MODULES
+      case PVEC_MODULE_FUNCTION:
+        print_string (module_format_fun_env (XMODULE_FUNCTION (obj)),
+                      printcharfun);
+        break;
+#endif
+
         case PVEC_OTHER:
         case PVEC_FREE:
           emacs_abort ();
@@ -2103,11 +2110,6 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
             printchar ('>', printcharfun);
             break;
           }
-
-        case Lisp_Misc_Module_Function:
-          print_string (module_format_fun_env (XMODULE_FUNCTION (obj)),
-                        printcharfun);
-          break;
 #endif
 
         case Lisp_Misc_Finalizer: