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xo-gc: add mutation log check in X1Collector.verify_ok()

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This commit is contained in:
Roland Conybeare 2026-03-28 17:06:30 -04:00
commit 5a383e89ce
2 changed files with 61 additions and 5 deletions
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9
include/xo/gc/DX1Collector.hpp
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@ -101,6 +101,15 @@ namespace xo {
std::uint32_t n_fwd_ = 0;
/** counts missing GCObject interface. Fatal if non-zero **/
std::uint32_t n_no_iface_ = 0;
/** live mlog entry refers to to-space, as expected **/
std::uint32_t n_mlog_vital_ = 0;
/** stale mlog entry. not troubling to verify these **/
std::uint32_t n_mlog_stale_ = 0;
/** live mlog entry refers to from-space. Fatal if non-zero **/
std::uint32_t n_mlog_from_ = 0;
/** live mlog entry refers to either some other generation or outside gc-space. Fatal if non-zero **/
std::uint32_t n_mlog_wild_ = 0;
};
// ----- DX1Collector -----

55
src/gc/DX1Collector.cpp
View file

@ -424,7 +424,7 @@ namespace xo {
// child pointer validity.
//
// Nested control reenters
// X1Collector::forward_inplace()
// X1Collector::forward_inplace() -> _verify_aux()
//
gco.forward_children(self);
} else {
@ -434,6 +434,49 @@ namespace xo {
}
}
}
// 4. scan mutation logs
for (Generation g(0); g + 1 < config_.n_generation_; ++g) {
const DArena * space = this->get_space(role::to_space(), g);
const DArena * from = this->get_space(role::from_space(), g);
// mutation log for generation g records *incoming* pointers
// from more senior generations; includes objects from *this*
// generation that are older (track since source promotes before
// destination)
//
for (const MutationLogEntry & mrecd : *(mlog_[role::to_space()][g])) {
// mutation log entries are only valid until the next assignment
// at the source location. Superseded entry may now point
// somewhere else. The snapshot member must however point
// to this generation, since that's preserved as long as the
// log entry survives.
void * orig_data = mrecd.snap().data();
void * curr_data = *mrecd.p_data();
if (orig_data == curr_data) {
// live mlog entry must point to to-space
if (space->contains_allocated(orig_data)) {
++verify_stats_.n_mlog_vital_;
} else if (from->contains(curr_data)) {
// verify failure.
++verify_stats_.n_mlog_from_;
} else {
// verify failure.
++verify_stats_.n_mlog_wild_;
}
} else {
// requirements on superseded log entry:
// - snapshot refers to to-space
//
// no requirements on current data, entry is superseded anyway
//
++verify_stats_.n_mlog_stale_;
}
}
}
}
// restore run state at end of verify cycle
@ -574,7 +617,11 @@ namespace xo {
xtag("n-from", verify_stats_.n_from_),
xtag("n-to", verify_stats_.n_to_),
xtag("n-fwd", verify_stats_.n_fwd_),
xtag("n-no-iface", verify_stats_.n_no_iface_));
xtag("n-no-iface", verify_stats_.n_no_iface_),
xtag("n-mlog-vital", verify_stats_.n_mlog_vital_),
xtag("n-mlog-stale", verify_stats_.n_mlog_stale_),
xtag("n-mlog-from", verify_stats_.n_mlog_from_),
xtag("n-mlog-wild", verify_stats_.n_mlog_wild_));
assert(ok);
}
@ -1230,8 +1277,8 @@ namespace xo {
if (src_g < dest_g) {
// young-to-old pointers don't need to be remembered,
// since a GC cycle that collects the old generation is guarnatted
// to also collect the young generation.
// since a GC cycle that collects an (old) generation is guarnatted
// to also collect all younger generations.
return;
}