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Factor AllocationId out of Address (#916)

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This lets us statically distinguish between code that works with arbitrary `Address`es and code that can only work with pointers to separately-allocated storage, and so we no longer need to worry about the latter code crashing at run-time (as `Heap::Deallocate` did) or silently doing the wrong thing (as `Heap::PrintAddress` did) if it's given the wrong kind of `Address`.
This commit is contained in:
Geoff Romer
2021-10-27 16:40:17 -07:00
committed by GitHub
parent 0da907fd2a
commit 0df9e8666c
8 changed files with 85 additions and 66 deletions
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executable_semantics/interpreter/heap.cpp
+19 -18
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@@ -9,12 +9,12 @@
namespace Carbon {
auto Heap::AllocateValue(Nonnull<const Value*> v) -> Address {
auto Heap::AllocateValue(Nonnull<const Value*> v) -> AllocationId {
// Putting the following two side effects together in this function
// ensures that we don't do anything else in between, which is really bad!
// Consider whether to include a copy of the input v in this function
// or to leave it up to the caller.
Address a(values_.size());
AllocationId a(values_.size());
values_.push_back(v);
alive_.push_back(true);
return a;
@@ -22,29 +22,29 @@ auto Heap::AllocateValue(Nonnull<const Value*> v) -> Address {
auto Heap::Read(const Address& a, SourceLocation source_loc)
-> Nonnull<const Value*> {
this->CheckAlive(a, source_loc);
return values_[a.index_]->GetField(arena_, a.field_path_, source_loc);
this->CheckAlive(a.allocation_, source_loc);
return values_[a.allocation_.index_]->GetField(arena_, a.field_path_,
source_loc);
}
void Heap::Write(const Address& a, Nonnull<const Value*> v,
SourceLocation source_loc) {
this->CheckAlive(a, source_loc);
values_[a.index_] =
values_[a.index_]->SetField(arena_, a.field_path_, v, source_loc);
this->CheckAlive(a.allocation_, source_loc);
values_[a.allocation_.index_] = values_[a.allocation_.index_]->SetField(
arena_, a.field_path_, v, source_loc);
}
void Heap::CheckAlive(const Address& address, SourceLocation source_loc) {
if (!alive_[address.index_]) {
void Heap::CheckAlive(AllocationId allocation, SourceLocation source_loc) {
if (!alive_[allocation.index_]) {
FATAL_RUNTIME_ERROR(source_loc)
<< "undefined behavior: access to dead value "
<< *values_[address.index_];
<< *values_[allocation.index_];
}
}
void Heap::Deallocate(const Address& address) {
CHECK(address.field_path_.IsEmpty());
if (alive_[address.index_]) {
alive_[address.index_] = false;
void Heap::Deallocate(AllocationId allocation) {
if (alive_[allocation.index_]) {
alive_[allocation.index_] = false;
} else {
FATAL_RUNTIME_ERROR_NO_LINE() << "deallocating an already dead value";
}
@@ -54,15 +54,16 @@ void Heap::Print(llvm::raw_ostream& out) const {
llvm::ListSeparator sep;
for (size_t i = 0; i < values_.size(); ++i) {
out << sep;
PrintAddress(Address(i), out);
PrintAllocation(AllocationId(i), out);
}
}
void Heap::PrintAddress(const Address& a, llvm::raw_ostream& out) const {
if (!alive_[a.index_]) {
void Heap::PrintAllocation(AllocationId allocation,
llvm::raw_ostream& out) const {
if (!alive_[allocation.index_]) {
out << "!!";
}
out << *values_[a.index_];
out << *values_[allocation.index_];
}
} // namespace Carbon