Re: port-with-print-state doesn't create a port? Or, when is a port not a port? :-)

[Ludovic Courtès]

Hi!

Doug Evans <address@hidden> skribis:

> The problem can be succinctly represented by the following:
>
> scheme@(guile-user)> (port? (port-with-print-state (current-output-port)))
> $3 = #f

I think the short answer is that it’s a very old API that’s essentially
unused internally.  For instance, make check passes with this patch:

index 122e035..8f4c969 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -255,6 +255,7 @@ scm_free_print_state (SCM print_state)
 SCM
 scm_i_port_with_print_state (SCM port, SCM print_state)
 {
+  abort ();
   if (SCM_UNBNDP (print_state))
     {
       if (SCM_PORT_WITH_PS_P (port))
@@ -596,8 +597,7 @@ iprin1 (SCM exp, SCM port, scm_print_state *pstate)
                SCM pwps, print = pstate->writingp ? g_write : g_display;
                if (SCM_UNPACK (print) == 0)
                  goto print_struct;
-               pwps = scm_i_port_with_print_state (port, pstate->handle);
-               pstate->revealed = 1;
+               pwps = port;
                scm_call_generic_2 (print, exp, pwps);
              }
            else
@@ -824,6 +824,7 @@ scm_prin1 (SCM exp, SCM port, int writingp)
 
   if (SCM_PORT_WITH_PS_P (port))
     {
+      abort ();
       pstate_scm = SCM_PORT_WITH_PS_PS (port);
       port = SCM_PORT_WITH_PS_PORT (port);
     }
@@ -1610,7 +1611,7 @@ scm_printer_apply (SCM proc, SCM exp, SCM port, 
scm_print_state *pstate)
 {
   pstate->revealed = 1;
   return scm_call_2 (proc, exp,
-                    scm_i_port_with_print_state (port, pstate->handle));
+                    port);
 }
 
 SCM_DEFINE (scm_port_with_print_state, "port-with-print-state", 1, 1, 0, 
diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm
index 42d7d78..2974ef6 100644
--- a/module/ice-9/boot-9.scm
+++ b/module/ice-9/boot-9.scm
@@ -1257,11 +1257,6 @@ VALUE."
 ;;
 ;; It should print OBJECT to PORT.
 
-(define (inherit-print-state old-port new-port)
-  (if (get-print-state old-port)
-      (port-with-print-state new-port (get-print-state old-port))
-      new-port))
-
 ;; 0: type-name, 1: fields, 2: constructor
 (define record-type-vtable
   (let ((s (make-vtable (string-append standard-vtable-fields "prprpw")

I think the problem it was trying to solve has been solved differently
(by explicitly passing the print state in the print.c code, for
instance), and can easily be solved differently.

> In the meantime, I can make struct printers be aware of the
> distinction and handle being passed port-with-print-state ports.

Do you actually need this associated state?

My first feeling is that we should deprecate and eventually remove this
API, given that it’s essentially unused and non-functional.

What do people think?

> P.S. How come scm_put[cs]_unlocked are inlined in ports.h?

What’s wrong with that?  (It probably doesn’t help much because
scm_lfwrite_unlocked isn’t inlined.)

Ludo’.