//: Reclaiming memory when it's no longer used.
:(scenario new_reclaim)
def main [
1:address:num <- new number:type
2:num <- copy 1:address:num # because 1 will get reset during abandon below
abandon 1:address:num
3:address:num <- new number:type # must be same size as abandoned memory to reuse
4:num <- copy 3:address:num
5:bool <- equal 2:num, 4:num
]
# both allocations should have returned the same address
+mem: storing 1 in location 5
//: When abandoning addresses we'll save them to a 'free list', segregated by size.
:(before "End routine Fields")
map<int, int> free_list;
:(before "End Primitive Recipe Declarations")
ABANDON,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "abandon", ABANDON);
:(before "End Primitive Recipe Checks")
case ABANDON: {
if (!inst.products.empty()) {
raise << maybe(get(Recipe, r).name) << "'abandon' shouldn't write to any products in '" << to_original_string(inst) << "'\n" << end();
break;
}
for (int i = 0; i < SIZE(inst.ingredients); ++i) {
if (!is_mu_address(inst.ingredients.at(i)))
raise << maybe(get(Recipe, r).name) << "ingredients of 'abandon' should be addresses, but ingredient " << i << " is '" << to_string(inst.ingredients.at(i)) << '\n' << end();
break;
}
break;
}
:(before "End Primitive Recipe Implementations")
case ABANDON: {
for (int i = 0; i < SIZE(current_instruction().ingredients); ++i) {
reagent/*copy*/ ingredient = current_instruction().ingredients.at(i);
canonize(ingredient);
abandon(get_or_insert(Memory, ingredient.value), payload_size(ingredient));
}
break;
}
:(code)
void abandon(int address, int payload_size) {
// clear memory
for (int curr = address; curr < address+payload_size; ++curr)
put(Memory, curr, 0);
// append existing free list to address
trace("abandon") << "saving " << address << " in free-list of size " << payload_size << end();
put(Memory, address, get_or_insert(Current_routine->free_list, payload_size));
put(Current_routine->free_list, payload_size, address);
}
:(after "Allocate Special-cases")
if (get_or_insert(Current_routine->free_list, size)) {
trace("abandon") << "picking up space from free-list of size " << size << end();
int result = get_or_insert(Current_routine->free_list, size);
trace("mem") << "new alloc from free list: " << result << end();
put(Current_routine->free_list, size, get_or_insert(Memory, result));
put(Memory, result, 0);
for (int curr = result; curr < result+size; ++curr) {
if (get_or_insert(Memory, curr) != 0) {
raise << maybe(current_recipe_name()) << "memory in free list was not zeroed out: " << curr << '/' << result << "; somebody wrote to us after free!!!\n" << end();
break; // always fatal
}
}
return result;
}
:(scenario new_differing_size_no_reclaim)
def main [
1:address:num <- new number:type
2:num <- copy 1:address:num
abandon 1:address:num
3:address:array:num <- new number:type, 2 # different size
4:num <- copy 3:address:array:num
5:bool <- equal 2:num, 4:num
]
# no reuse
+mem: storing 0 in location 5
:(scenario new_reclaim_array)
def main [
1:address:array:num <- new number:type, 2
2:num <- copy 1:address:array:num
abandon 1:address:array:num
3:address:array:num <- new number:type, 2 # same size
4:num <- copy 3:address:array:num
5:bool <- equal 2:num, 4:num
]
# both calls to new returned identical addresses
+mem: storing 1 in location 5