1 files changed, 153 insertions, 0 deletions
diff --git a/archive/1.vm/036abandon.cc b/archive/1.vm/036abandon.cc
new file mode 100644
index 00000000..a1f66523
--- /dev/null
+++ b/archive/1.vm/036abandon.cc
@@ -0,0 +1,153 @@
+//: Reclaiming memory when it's no longer used.
+
+void test_new_reclaim() {
+  run(
+      "def main [\n"
+      "  10:&:num <- new number:type\n"
+      "  20:num <- deaddress 10:&:num\n"
+      "  abandon 10:&:num\n"
+      "  30:&:num <- new number:type\n"  // must be same size as abandoned memory to reuse
+      "  40:num <- deaddress 30:&:num\n"
+      "  50:bool <- equal 20:num, 40:num\n"
+      "]\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      // both allocations should have returned the same address
+      "mem: storing 1 in location 50\n"
+  );
+}
+
+//: When abandoning addresses we'll save them to a 'free list', segregated by size.
+
+//: Before, suppose variable V contains address A which points to payload P:
+//:   location V contains an alloc-id N
+//:   location V+1 contains A
+//:   location A contains alloc-id N
+//:   location A+1 onwards contains P
+//: Additionally, suppose the head of the free list is initially F.
+//: After abandoning:
+//:   location V contains invalid alloc-id -1
+//:   location V+1 contains 0
+//:   location A contains invalid alloc-id N
+//:   location A+1 contains the previous head of free-list F
+
+:(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+/*skip alloc id*/1), payload_size(ingredient));
+//?     cerr << "clear after abandon: " << ingredient.value << '\n';
+    put(Memory, /*alloc id*/ingredient.value, /*invalid*/-1);
+    put(Memory, /*address*/ingredient.value+1, 0);
+  }
+  break;
+}
+
+:(code)
+void abandon(int address, int payload_size) {
+  put(Memory, address, /*invalid alloc-id*/-1);
+//?   cerr << "abandon: " << address << '\n';
+  // clear rest of payload
+  for (int curr = address+1;  curr < address+payload_size;  ++curr)
+    put(Memory, curr, 0);
+  // append existing free list to address
+  trace(Callstack_depth+1, "abandon") << "saving " << address << " in free-list of size " << payload_size << end();
+  put(Memory, address+/*skip invalid alloc-id*/1, get_or_insert(Current_routine->free_list, payload_size));
+  put(Current_routine->free_list, payload_size, address);
+}
+
+int payload_size(reagent/*copy*/ x) {
+  x.properties.push_back(pair<string, string_tree*>("lookup", NULL));
+  lookup_memory_core(x, /*check_for_null*/false);
+  return size_of(x)+/*alloc id*/1;
+}
+
+:(after "Allocate Special-cases")
+if (get_or_insert(Current_routine->free_list, size)) {
+  trace(Callstack_depth+1, "abandon") << "picking up space from free-list of size " << size << end();
+  int result = get_or_insert(Current_routine->free_list, size);
+  trace(Callstack_depth+1, "mem") << "new alloc from free list: " << result << end();
+  put(Current_routine->free_list, size, get_or_insert(Memory, result+/*skip alloc id*/1));
+  // clear 'deleted' tag
+  put(Memory, result, 0);
+  // clear next pointer
+  put(Memory, result+/*skip alloc id*/1, 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;
+}
+
+:(code)
+void test_new_differing_size_no_reclaim() {
+  run(
+      "def main [\n"
+      "  1:&:num <- new number:type\n"
+      "  2:num <- deaddress 1:&:num\n"
+      "  abandon 1:&:num\n"
+      "  3:&:@:num <- new number:type, 2\n"  // different size
+      "  4:num <- deaddress 3:&:@:num\n"
+      "  5:bool <- equal 2:num, 4:num\n"
+      "]\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      // no reuse
+      "mem: storing 0 in location 5\n"
+  );
+}
+
+void test_new_reclaim_array() {
+  run(
+      "def main [\n"
+      "  10:&:@:num <- new number:type, 2\n"
+      "  20:num <- deaddress 10:&:@:num\n"
+      "  abandon 10:&:@:num\n"
+      "  30:&:@:num <- new number:type, 2\n"  // same size
+      "  40:num <- deaddress 30:&:@:num\n"
+      "  50:bool <- equal 20:num, 40:num\n"
+      "]\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      // both calls to new returned identical addresses
+      "mem: storing 1 in location 50\n"
+  );
+}
+
+void test_lookup_of_abandoned_address_raises_error() {
+  Hide_errors = true;
+  run(
+      "def main [\n"
+      "  1:&:num <- new num:type\n"
+      "  3:&:num <- copy 1:&:num\n"
+      "  abandon 1:&:num\n"
+      "  5:num/raw <- copy *3:&:num\n"
+      "]\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "error: main: address is already abandoned in '5:num/raw <- copy *3:&:num'\n"
+  );
+}