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fix over-eager shortcut in the implementaiton of continuation jumps

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Don't jump past a prompt when jumping to a continuation that is
a prefix of the current one.

Reported by Max New
This commit is contained in:
Matthew Flatt 2014-12-03 06:59:08 -07:00
parent 776dd0f5bb
commit f3dba3eb6b
2 changed files with 26 additions and 2 deletions
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13
pkgs/racket-pkgs/racket-test/tests/racket/prompt-tests.rktl
View File

@ -322,6 +322,19 @@
(test-breaks-ok)
;; Make sure a jump to an enclosing continuation doesn't
;; skip over a prompt:
(test 25 values (+ 5
(call-with-continuation-prompt
(lambda ()
(+ 1
(call/cc
(lambda (k)
(+ 17
(call-with-continuation-prompt
(lambda ()
(k 1)))))))))))
;; ----------------------------------------
;; Overlapping continuations

15
racket/src/racket/src/eval.c
View File

@ -1478,6 +1478,10 @@ static Scheme_Prompt *lookup_cont_prompt(Scheme_Cont *c,
Scheme_Prompt *prompt;
Scheme_Object *pt;
if (!c->runstack_copied)
/* This continuation is the same as another... */
c = c->buf_ptr->buf.cont;
pt = c->prompt_tag;
if (SCHEME_NP_CHAPERONEP(pt))
pt = SCHEME_CHAPERONE_VAL(pt);
@ -1615,10 +1619,17 @@ Scheme_Object *scheme_jump_to_continuation(Scheme_Object *obj, int num_rands, Sc
c = (Scheme_Cont *)obj;
/* Shortcut: if the target continuation is an extension of the current
continuation, and if no prompt is in the way, then escape directly. */
if (can_ec
&& c->escape_cont
&& scheme_escape_continuation_ok(c->escape_cont))
scheme_escape_to_continuation(c->escape_cont, num_rands, rands, (Scheme_Object *)c);
&& scheme_escape_continuation_ok(c->escape_cont)) {
prompt = lookup_cont_prompt(c, &prompt_mc, &prompt_pos, LOOKUP_NO_PROMPT);
if (!prompt || (prompt->id
&& (prompt->id == c->prompt_id)
&& !prompt_mc))
scheme_escape_to_continuation(c->escape_cont, num_rands, rands, (Scheme_Object *)c);
}
if (num_rands != 1) {
GC_CAN_IGNORE Scheme_Object **vals;