fix potential PROTECT/UNPROTECT issues in C code - #469
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jeroen
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Aug 5, 2026
| Rf_errorcall(R_NilValue, "%s", errbuf); | ||
| } | ||
| SEXP out = ParseValue(node, bigint); | ||
| SEXP out = PROTECT(ParseValue(node, bigint)); |
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This is really not needed, yajl_tree_free is not an R call so it won't have any effect on gc.
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Thanks, you're right -- this was just meant to be defensive. The only potential issue is in push_parser.c, since (in theory) the evaluation order of the expressions is undefined. I'll trim this PR to the minimal set of changes that are worth considering here.
Per review feedback, drop the defensive-only PROTECT additions in parse.c, r-base64.c, and row_collapse.c -- none of those windows contain allocating calls. Also drop the UNPROTECT before the goto in push_parser.c, since Rf_error() unwinds the protection stack itself. Keep the evaluation-order fix in push_parser.c, and NUL-termination of the error buffer after strncpy.
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This fixes a PROTECT-related issue in
push_parser.c, found via a manual audit.PROTECT()calls were nested inside the argument list ofRf_lang4(). Since C argument evaluation order is unspecified, a compiler may evaluateRf_allocVector()andRf_ScalarInteger()before eitherPROTECT()runs, leaving a fresh allocation unprotected while another allocation (and potentially GC) occurs. The objects are now allocated and protected in separate statements.Also guarantees NUL-termination of the error buffer after
strncpy(), which does not terminate on truncation.This PR originally also added defensive
PROTECT()calls inparse.c,r-base64.c, androw_collapse.c. As @jeroen noted in review, those windows contain no allocating calls, so the protection had no effect; they've been dropped.Tested with
R CMD INSTALLand the testthat suite, and exercised the touched paths (including the parse-error path) undergctorture(TRUE).