Remove port free functions; just close instead

* libguile/ports.h (scm_t_port_type_flags): Replace
  SCM_PORT_TYPE_HAS_FLUSH with SCM_PORT_TYPE_NEEDS_CLOSE_ON_GC.
  (scm_t_ptob_descriptor): Remove free function.
* libguile/ports.c (scm_set_port_needs_close_on_gc): New function.
  (scm_set_port_flush): Don't set flags.
  (scm_c_make_port_with_encoding, scm_close_port): Use the new flag to
  determine when to add a finalizer and also when to include the port in
  the weak set.
  (scm_set_port_free): Remove.
  (do_close, finalize_port): Close port instead of calling free
  function.
* libguile/r6rs-ports.c (initialize_transcoded_ports):
* libguile/vports.c (scm_make_sfptob):
* libguile/fports.c (scm_make_fptob): Mark these ports as needing close
  on GC.
* libguile/fports.c (fport_free): Remove.
* NEWS: Update.
* doc/ref/api-io.texi (Port Implementation): Update.

1 files changed, 11 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 0ab0b395c..24c43b7a0 100644
--- a/NEWS
+++ b/NEWS
@@ -24,6 +24,17 @@ as arguments to the `setvbuf' function.
 Port mark functions have not been called since the switch to the BDW
 garbage collector.
 
+** Remove `scm_set_port_free'
+
+It used to be that if an open port became unreachable, a special "free"
+function would be called instead of the "close" function.  Now that the
+BDW-GC collector allows us to run arbitrary code in finalizers, we can
+simplify to just call "close" on the port and remove the separate free
+functions.  Note that hooking into the garbage collector has some
+overhead.  For that reason Guile exposes a new interface,
+`scm_set_port_needs_close_on_gc', allowing port implementations to
+indicate to Guile whether they need closing on GC or not.
+
 
 Changes in 2.1.2 (changes since the 2.1.1 alpha release):