protect evaluated lazy call in new_error_subscript_type() - #2174
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kevinushey wants to merge 1 commit into
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protect evaluated lazy call in new_error_subscript_type()#2174kevinushey wants to merge 1 commit into
kevinushey wants to merge 1 commit into
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The result of r_lazy_eval_protect() is a freshly allocated quote() wrapper whenever the lazy call evaluates to a language object. It was left unprotected while r_call_n() allocated the argument pairlist, so a GC during those allocations could collect it, corrupting the call field of the condition (or crashing R). KEEP() it like every other r_lazy_eval_protect() call site and bump the matching FREE(). Fixes r-lib#2173.
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Fixes #2173.
new_error_subscript_type()was the onlyr_lazy_eval_protect()call site in the package that did notKEEP()its result. When the lazy call evaluates to a language object,r_lazy_eval_protect()returns a freshly allocatedquote()wrapper, which sat unprotected in theargsarray whiler_call_n()allocated the cons cells of the argument pairlist. A GC during those allocations collects the wrapper; the freed node is typically reused by the nextRf_cons(), so the condition'scallfield ends up as a cyclic pairlist pointing into the condition call's own arguments (and this can just as well crash R).This PR
KEEP()s the result (matching the call sites inconditions.c,match.c, andlist-combine.c) and bumps the matchingFREE(3)toFREE(4).Verified with the
gctorture()repro from #2173:conditionCall(cnd)becomes a self-referential dotted pair listconditionCall(cnd)isfoo(bar)as expectedtestthat::test_local(filter = "subscript")passes (262 tests).