Reimplement dynamic states

There are two goals: one, to use less memory per dynamic state in order
to allow millions of dynamic states to be allocated in light-weight
threading scenarios.  The second goal is to prevent dynamic states from
being actively mutated in two threads at once.  This second goal does
mean that dynamic states object that escape into scheme are now copies
that won't receive further updates; an incompatible change, but one
which we hope doesn't affect anyone.

* libguile/cache-internal.h: New file.
* libguile/fluids.c (is_dynamic_state, get_dynamic_state)
  (save_dynamic_state, restore_dynamic_state, add_entry)
  (copy_value_table): New functions.
  (scm_i_fluid_print, scm_i_dynamic_state_print): Move up.
  (new_fluid): No need for a number.
  (scm_fluid_p: scm_is_fluid): Inline IS_FLUID uses.
  (fluid_set_x, fluid_ref): Adapt to dynamic state changes.
  (scm_fluid_set_x, scm_fluid_unset_x): Call fluid_set_x.
  (scm_swap_fluid): Rewrite in terms of fluid_ref and fluid_set.
  (swap_fluid): Use internal fluid_set_x.
  (scm_i_make_initial_dynamic_state): Adapt to dynamic state
  representation change.
  (scm_dynamic_state_p, scm_is_dynamic_state): Use new accessors.
  (scm_current_dynamic_state): Use make_dynamic_state.
  (scm_dynwind_current_dynamic_state): Use new accessor.
* libguile/fluids.h: Remove internal definitions.  Add new struct
  definition.
* libguile/threads.h (scm_i_thread): Use scm_t_dynamic_state for dynamic
  state.
* libguile/threads.c (guilify_self_1, guilify_self_2):
  (scm_i_init_thread_for_guile, scm_init_guile):
  (scm_call_with_new_thread):
  (scm_init_threads, scm_init_threads_default_dynamic_state): Adapt to
  scm_i_thread change.
  (scm_i_with_guile, with_guile): Remove "and parent" suffix.
  (scm_i_reset_fluid): Remove unneeded function.
* doc/ref/api-scheduling.texi (Fluids and Dynamic States): Remove
  scm_make_dynamic_state docs.  Update current-dynamic-state docs.
* libguile/vm-engine.c (vm_engine): Update fluid-ref and fluid-set!
  inlined fast paths for dynamic state changes.
* libguile/vm.c (vm_error_unbound_fluid): Remove now-unused function.
* NEWS: Update.
* module/ice-9/deprecated.scm (make-dynamic-state): New definition.
* libguile/deprecated.h:
* libguile/deprecated.c (scm_make_dynamic_state): Move here.
* libguile/__scm.h (scm_t_dynamic_state): New typedef.
* libguile/dynstack.h:
* libguile/dynstack.c (scm_dynstack_push_fluid):
  (scm_dynstack_unwind_fluid): Take raw dynstate in these internal
  functions.
* libguile/throw.c (catch): Adapt to dynstack changes.

1 files changed, 17 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 66fd2b03a..809f5ac63 100644
--- a/NEWS
+++ b/NEWS
@@ -87,6 +87,18 @@ Guile itself, though their join value was always `#f'.  This is no
 longer the case; attempting to join a foreign thread will throw an
 error.
 
+** Dynamic states capture values, not locations
+
+Dynamic states used to capture the locations of fluid-value
+associations.  Capturing the current dynamic state then setting a fluid
+would result in a mutation of that captured state.  Now capturing a
+dynamic state simply captures the current values, and calling
+`with-dynamic-state' copies those values into the Guile virtual machine
+instead of aliasing them in a way that could allow them to be mutated in
+place.  This change allows Guile's fluid variables to be thread-safe.
+To capture the locations of a dynamic state, use partial continuations
+instead.
+
 * New deprecations
 ** Arbiters deprecated
 
@@ -122,6 +134,11 @@ This was a facility that predated threads, was unused as far as we can
 tell, and was never documented.  Still, a grep of your code for
 dynamic-root or dynamic_root would not be amiss.
 
+** `make-dynamic-state' deprecated
+
+Use `current-dynamic-state' to get an immutable copy of the current
+fluid-value associations.
+
 * Bug fixes
 ** cancel-thread uses asynchronous interrupts, not pthread_cancel