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xo-gc: bugfixes for GCObjectStore, unit test exapnded

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In particular: drop casual assignment to DList.rest_,
will break acyclic assumption of DList.size()
This commit is contained in:
Roland Conybeare 2026-04-11 16:51:52 -04:00
commit c4eb58f6ff
5 changed files with 368 additions and 194 deletions
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89
src/gc/GCObjectStore.cpp
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@ -13,6 +13,7 @@
#include <xo/stringtable2/String.hpp>
#include <xo/arena/DArenaIterator.hpp>
#include <xo/arena/backtrace.hpp>
#include <xo/facet/TypeRegistry.hpp>
#include <xo/indentlog/scope.hpp>
@ -31,8 +32,9 @@ namespace xo {
namespace mm {
GCObjectStore::GCObjectStore(const GCObjectStoreConfig & cfg)
: config_{cfg}
GCObjectStore::GCObjectStore(const GCObjectStoreConfig & cfg,
X1VerifyStats * p_verify_stats)
: config_{cfg}, p_verify_stats_{p_verify_stats}
{
assert(config_.arena_config_.header_.size_bits_ +
config_.arena_config_.header_.age_bits_ +
@ -473,6 +475,36 @@ namespace xo {
return (g < upto);
}
#ifdef NOT_YET
void
GCObjectStore::visit_child(VisitReason reason,
AGCObject * lhs_iface,
void ** lhs_data)
{
// MAYBE: adapter distinct from DX1Collector that supports GCObjectVisitor facet,
// calls DX1Collector::_verify_aux()
switch (reason.code()) {
case VisitReason::code::forward:
{
Generation upto = runstate_.gc_upto();
// called during collection phase
this->forward_inplace_aux
(this->ref<AGCObjectVisitor>(), lhs_iface, lhs_data, upto);
break;
}
case VisitReason::code::verify:
// called during verify_ok
gco_store_.verify_aux(lhs_iface, *lhs_data);
break;
default:
// should be unreachable
assert(false);
}
}
#endif
void
GCObjectStore::forward_inplace_aux(obj<AGCObjectVisitor> gc,
AGCObject * lhs_iface,
@ -558,7 +590,9 @@ namespace xo {
*
* This is guaranteed anyway, by alignment rules
*/
assert(alloc_z >= sizeof(uintptr_t));
if (alloc_z < sizeof(uintptr_t)) {
assert(false);
}
if (this->is_forwarding_header(alloc_hdr)) {
/* *lhs_data already refers to a forwarding pointer */
@ -661,10 +695,9 @@ namespace xo {
void
GCObjectStore::verify_aux(AGCObject * iface,
void * data,
X1VerifyStats * p_verify_stats)
void * data)
{
//scope log(XO_DEBUG(config_.debug_flag_), xtag("data", data));
scope log(XO_DEBUG(config_.debug_flag_));
(void)iface;
@ -678,14 +711,16 @@ namespace xo {
if (!g2.is_sentinel()) {
// verify failure - live pointer still refers to from-space
++(p_verify_stats->n_from_);
print_backtrace_dwarf(true /*demangle*/);
++(p_verify_stats_->n_from_);
} else {
++(p_verify_stats->n_ext_);
++(p_verify_stats_->n_ext_);
}
} else {
assert(this->contains(Role::to_space(), data));
++(p_verify_stats->n_to_);
++(p_verify_stats_->n_to_);
}
}
@ -733,8 +768,7 @@ namespace xo {
}
void
GCObjectStore::verify_ok(obj<AGCObjectVisitor> gc,
X1VerifyStats * p_verify_stats) noexcept
GCObjectStore::verify_ok(obj<AGCObjectVisitor> gc) noexcept
{
for (Generation g(0); g < config_.n_generation_; ++g) {
const DArena * space = this->get_space(Role::to_space(), g);
@ -742,7 +776,7 @@ namespace xo {
for (const AllocInfo & info : *space) {
if (info.is_forwarding_tseq()) {
++(p_verify_stats->n_fwd_);
++(p_verify_stats_->n_fwd_);
} else {
typeseq tseq(info.tseq());
@ -755,15 +789,9 @@ namespace xo {
// assembled fop for gc-aware object
obj<AGCObject> gco(iface, const_cast<void *>(data));
// forward_children is hijacked here to verify
// child pointer validity.
//
// Nested control reenters
// X1Collector::forward_inplace() -> _verify_aux()
//
gco.visit_gco_children(VisitReason::forward(), gc);
gco.visit_gco_children(VisitReason::verify(), gc);
} else {
++(p_verify_stats->n_no_iface_);
++(p_verify_stats_->n_no_iface_);
continue;
}
}
@ -803,7 +831,8 @@ namespace xo {
void *
GCObjectStore::deep_move_root(obj<AGCObjectVisitor> gc,
obj<AGCObject> from_src,
const AGCObject * root_iface,
void ** root_data,
Generation upto)
{
// NOTE:
@ -815,22 +844,23 @@ namespace xo {
scope log(XO_DEBUG(config_.debug_flag_));
if (!from_src)
if (!root_data || !*root_data)
return nullptr;
bool src_in_from_space = this->contains(Role::from_space(),
from_src.data());
bool src_in_from_space = this->contains(Role::from_space(), *root_data);
if (src_in_from_space) {
return this->_deep_move_gc_owned(gc, from_src.data(), upto);
*root_data = this->_deep_move_gc_owned(gc, *root_data, upto);
} else {
// we aren't moving from_src, it's not gc-owned.
// However weare moving all its gc-owned children
// However we are moving all its gc-owned children
GCMoveCheckpoint gray_lo_v
= this->snap_move_checkpoint(upto);
from_src.visit_gco_children(VisitReason::forward(), gc);
auto root = obj<AGCObject>(root_iface, *root_data);
root.visit_gco_children(VisitReason::forward(), gc);
// For each generation g:
// traverse objects newer than gray_lo_v[g], to make sure children
@ -840,8 +870,11 @@ namespace xo {
//
this->_forward_children_until_fixpoint(gc, upto, gray_lo_v);
return from_src.data();
// reminder: *root_data preserved
}
return *root_data;
}
void *