protect new cons cell in named StretchyList::push_back() - #1490
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kevinushey wants to merge 1 commit into
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protect new cons cell in named StretchyList::push_back()#1490kevinushey wants to merge 1 commit into
kevinushey wants to merge 1 commit into
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The named variant of push_back() allocated the new cons cell before constructing the Symbol for its tag. If the tag name was not yet interned, Rf_install() could allocate and trigger a garbage collection that reclaimed the still-unreachable cell. Construct the Symbol first, matching push_front(). Fixes #1489.
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Fixes #1489.
The named variant of
StretchyList::push_back()allocated the new cons cell before constructing theSymbolfor its tag. If the tag name was not yet interned,Rf_install()could allocate and trigger a garbage collection that reclaimed the still-unreachable cell;SET_TAG()then wrote into a reclaimed node, which was subsequently linked into the list. See #1489 for a reproducible example viaRcpp::sourceCpp()andgctorture().The fix constructs the
Symbolbefore callingRf_cons(), matching the ordering already used by the named variant ofpush_front().Also adds a regression test exercising named
push_back()with a freshly generated (never-interned) tag name undergctorture(); the test fails without the header change and passes with it.Checklist
R CMD checkstill passes all tests (checked locally withRunAllRcppTests=yeson R 4.6.1;--no-manual --no-vignettes, so the only flagged items were two vignette-packaging warnings from the local--no-build-vignettesbuild)