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bytecode compiler: don't discard another set! that should error

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The repair in 7176fc4253 did not make the no-discard decision stick
well enough for some cases. Robby found this bug using the Redex model
and random testing, too.
This commit is contained in:
Matthew Flatt 2018-08-21 20:48:44 -06:00
parent 16e496b0c5
commit 974988fe3c
2 changed files with 11 additions and 1 deletions
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6
pkgs/racket-test-core/tests/racket/letrec.rktl
View File

@ -173,4 +173,10 @@
(letrec ((B (begin (set! B B) 1))) 1)
letrec-exn?)
(err/rt-test
(list (begin
(letrec ((x (set! x x))) 0)
0))
letrec-exn?)
(report-errs)

6
racket/src/racket/src/compile.c
View File

@ -656,6 +656,9 @@ static Scheme_Object *set_compile (Scheme_Object *form, Scheme_Comp_Env *env)
if (((Scheme_IR_Toplevel *)var)->instance_pos != -1)
scheme_wrong_syntax(NULL, form, name, "cannot mutate imported variable");
SCHEME_IR_TOPLEVEL_FLAGS(((Scheme_IR_Toplevel *)var)) |= SCHEME_IR_TOPLEVEL_MUTATED;
} else if (SAME_TYPE(SCHEME_TYPE(var), scheme_ir_local_type)) {
if (((Scheme_IR_Local *)var)->compile.keep_assignment)
((Scheme_IR_Local *)var)->compile.keep_assignment = 2; /* keep permanently */
}
env = scheme_set_comp_env_name(env, SCHEME_STX_SYM(name));
@ -1091,7 +1094,8 @@ static Scheme_Object *do_let_compile (Scheme_Object *form, Scheme_Comp_Env *orig
lv->value = rhs;
for (j = lv->count; j--; ) {
lv->vars[j]->compile.keep_assignment = 0;
if (lv->vars[j]->compile.keep_assignment < 2)
lv->vars[j]->compile.keep_assignment = 0;
}
/* Record when this binding doesn't use any or later bindings in