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author | Andy Wingo <wingo@pobox.com> | 2017-02-07 09:28:39 +0100 |
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committer | Andy Wingo <wingo@pobox.com> | 2017-02-07 09:57:55 +0100 |
commit | 498f3f95684361f3591106a8f9cb9065fd649288 (patch) | |
tree | 70a8e33d1ea25c54c273a3cbe347010403dfb07c /doc/ref/api-control.texi | |
parent | 81e9a128c146ccd495846ecbf664b3fd2855baf1 (diff) | |
download | guile-498f3f95684361f3591106a8f9cb9065fd649288.tar.gz |
Avoid stacks in dynamically-bound values
* libguile/dynstack.h:
* libguile/dynstack.c (scm_dynstack_find_old_fluid_value): New
function.
* libguile/fluids.c (saved_dynamic_state_ref): New helper.
(scm_fluid_ref): Fix docstring.
(scm_fluid_ref_star): New function allowing access to previous values
for a fluid.
(scm_dynamic_state_ref): New internal function.
* libguile/fluids.h: Add scm_fluid_ref_star and scm_dynamic_state_ref.
* libguile/stacks.c (scm_stack_id): Adapt to %stacks not being a chain.
* libguile/throw.c (catch, throw_without_pre_unwind): Adapt to
%exception-handlers not being a chain.
* module/ice-9/boot-9.scm (catch, dispatch-exception): Instead of having
%exception-handlers be a chain, use fluid-ref* to access the chain
that is in place at the time the exception is thrown. Prevents
unintended undelimited capture of the current exception handler stack
by a delimited "catch".
(%start-stack): Similarly, don't be a chain.
* module/system/repl/debug.scm (frame->stack-vector):
* module/system/repl/error-handling.scm (call-with-error-handling):
* module/ice-9/save-stack.scm (save-stack): Adapt to %stacks not being a
chain.
* test-suite/tests/exceptions.test ("delimited exception handlers"): Add
tests.
* doc/ref/api-control.texi (Fluids and Dynamic States): Add docs.
Diffstat (limited to 'doc/ref/api-control.texi')
-rw-r--r-- | doc/ref/api-control.texi | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/doc/ref/api-control.texi b/doc/ref/api-control.texi index 73fbe3607..77d98b44e 100644 --- a/doc/ref/api-control.texi +++ b/doc/ref/api-control.texi @@ -1765,6 +1765,21 @@ a runtime error. Set the value associated with @var{fluid} in the current dynamic root. @end deffn +@deffn {Scheme Procedure} fluid-ref* fluid depth +@deffnx {C Function} scm_fluid_ref_star (fluid, depth) +Return the @var{depth}th oldest value associated with @var{fluid} in the +current thread. If @var{depth} equals or exceeds the number of values +that have been assigned to @var{fluid}, return the default value of the +fluid. @code{(fluid-ref* f 0)} is equivalent to @code{(fluid-ref f)}. + +@code{fluid-ref*} is useful when you want to maintain a stack-like +structure in a fluid, such as the stack of current exception handlers. +Using @code{fluid-ref*} instead of an explicit stack allows any partial +continuation captured by @code{call-with-prompt} to only capture the +bindings made within the limits of the prompt instead of the entire +continuation. @xref{Prompts}, for more on delimited continuations. +@end deffn + @deffn {Scheme Procedure} fluid-unset! fluid @deffnx {C Function} scm_fluid_unset_x (fluid) Disassociate the given fluid from any value, making it unbound. |