Add Struct.pre_initialize (#15896)

Author: HertzDevil

spec/compiler/semantic/primitives_spec.cr

@@ -451,4 +451,57 @@ describe "Semantic: primitives" do
         CRYSTAL
     end
   end
+
+  describe "Struct.pre_initialize" do
+    def_struct_pre_initialize = <<-CRYSTAL
+      struct Struct
+        @[Primitive(:pre_initialize)]
+        def self.pre_initialize(address : Pointer) : Nil
+          {% @type %}
+        end
+      end
+      CRYSTAL
+
+    it "errors on abstract type" do
+      assert_error <<-CRYSTAL, "Can't pre-initialize abstract struct Foo"
+        #{def_struct_pre_initialize}
+
+        abstract struct Foo
+        end
+
+        x = 1
+        Foo.pre_initialize(pointerof(x))
+        CRYSTAL
+    end
+
+    it "errors on virtual abstract type" do
+      assert_error <<-CRYSTAL, "Can't pre-initialize abstract struct Foo"
+        #{def_struct_pre_initialize}
+
+        abstract struct Foo
+        end
+
+        struct Bar < Foo
+        end
+
+        x = 1
+        Bar.as(Foo.class).pre_initialize(pointerof(x))
+        CRYSTAL
+    end
+
+    it "errors on abstract pointee type" do
+      assert_error <<-CRYSTAL, "Can't pre-initialize struct using pointer to abstract struct"
+        #{def_struct_pre_initialize}
+
+        abstract struct Foo
+        end
+
+        struct Bar < Foo
+        end
+
+        x = uninitialized Foo
+        Bar.pre_initialize(pointerof(x))
+        CRYSTAL
+    end
+  end
 end

spec/primitives/struct_spec.cr

@@ -0,0 +1,55 @@
+require "spec"
+
+private struct Foo
+  getter i : Int64
+  getter str = "abc"
+
+  def initialize(@i)
+  end
+
+  def initialize(@str, @i)
+  end
+end
+
+private struct Bar
+  getter x : UInt8[128]
+
+  def initialize(@x)
+  end
+end
+
+private struct Inner
+end
+
+private struct Outer
+  @x = Inner.new
+end
+
+describe "Primitives: struct" do
+  describe ".pre_initialize" do
+    it "doesn't fail on complex ivar initializer if value is discarded (#14325)" do
+      bar = uninitialized Outer
+      Outer.pre_initialize(pointerof(bar))
+      1
+    end
+
+    it "zeroes the instance data" do
+      bar = uninitialized Bar
+      Slice.new(pointerof(bar).as(UInt8*), sizeof(Bar)).fill(0xFF)
+      Bar.pre_initialize(pointerof(bar))
+      bar.x.all?(&.zero?).should be_true
+    end
+
+    it "runs inline instance initializers" do
+      foo = uninitialized Foo
+      Foo.pre_initialize(pointerof(foo)).should be_nil
+      foo.str.should eq("abc")
+    end
+
+    it "works when address is on the heap" do
+      foo_buffer = Pointer(Foo).malloc(1)
+      Foo.pre_initialize(foo_buffer)
+      foo_buffer.value.str.should eq("abc")
+    end
+  end
+end

src/compiler/crystal/codegen/primitives.cr

@@ -823,14 +823,14 @@ class Crystal::CodeGenVisitor
   end
 
   def codegen_primitive_pre_initialize(node, target_def, call_args)
-    type = node.type
+    type = context.type.instance_type
 
     base_type = type.is_a?(VirtualType) ? type.base_type : type
 
     ptr = call_args[target_def.owner.passed_as_self? ? 1 : 0]
     pre_initialize_aggregate base_type, llvm_struct_type(base_type), ptr
 
-    @last = cast_to ptr, type
+    @last = type.struct? ? llvm_nil : cast_to ptr, type
   end
 
   def codegen_primitive_pointer_malloc(node, target_def, call_args)

src/compiler/crystal/interpreter/instructions.cr

@@ -1282,7 +1282,10 @@ require "./repl"
         push:       true,
         code:       begin
           pointer.clear(size)
-          pointer.as(Int32*).value = type_id
+          unless type_id == 0
+            # 0 stands for any non-reference type
+            pointer.as(Int32*).value = type_id
+          end
           pointer
         end,
       },

src/compiler/crystal/interpreter/primitives.cr

@@ -187,10 +187,12 @@ class Crystal::Repl::Compiler
           scope.instance_type
         end
 
-      accept_call_members(node)
+      accept_call_args(node)
 
-      dup sizeof(Pointer(Void)), node: nil
-      reset_class(aligned_instance_sizeof_type(type), type_id(type), node: node)
+      # 0 stands for any non-reference type in `reset_class`
+      # (normally 0 stands for `Nil` so there is no conflict here)
+      type_id = type.struct? ? 0 : type_id(type)
+      reset_class(aligned_instance_sizeof_type(type), type_id, node: node)
 
       initializer_compiled_defs = @context.type_instance_var_initializers(type)
       unless initializer_compiled_defs.empty?
@@ -202,6 +204,11 @@ class Crystal::Repl::Compiler
           call compiled_def, node: nil
         end
       end
+
+      # `Struct.pre_initialize` does not return a pointer, so always discard it
+      if !@wants_value || type.struct?
+        pop(sizeof(Pointer(Void)), node: nil)
+      end
     when "tuple_indexer_known_index"
       unless @wants_value
         accept_call_members(node)

src/compiler/crystal/semantic/main_visitor.cr

@@ -2364,17 +2364,22 @@ module Crystal
     end
 
     def visit(node : Primitive)
+      case node.name
+      when "pre_initialize"
+        return visit_pre_initialize node
+      end
+
       # If the method where this primitive is defined has a return type, use it
       if return_type = typed_def.return_type
         node.type = (path_lookup || scope).lookup_type(return_type, free_vars: free_vars)
         return false
       end
 
+      # TODO: move these into the case expression above and add return types to
+      # their corresponding methods
       case node.name
       when "allocate"
         visit_allocate node
-      when "pre_initialize"
-        visit_pre_initialize node
       when "pointer_malloc"
         visit_pointer_malloc node
       when "pointer_set"
@@ -2478,35 +2483,46 @@ module Crystal
 
       case instance_type
       when GenericClassType
-        node.raise "Can't pre-initialize instance of generic class #{instance_type} without specifying its type vars"
+        node.raise "Can't pre-initialize instance of #{instance_type.type_desc} #{instance_type} without specifying its type vars"
       when UnionType
         node.raise "Can't pre-initialize instance of a union type"
-      else
-        if instance_type.abstract?
-          if instance_type.virtual?
-            # This is the same as `.initialize`
-            base_type = instance_type.devirtualize
+      end
 
-            extra = Call.new(
-              nil,
-              "raise",
-              StringLiteral.new("Can't pre-initialize abstract class #{base_type}"),
-              global: true).at(node)
-            extra.accept self
+      if instance_type.abstract?
+        if instance_type.virtual? && !instance_type.struct?
+          # This is the same as `.initialize`
+          base_type = instance_type.devirtualize
 
-            # This `extra` will replace the Primitive node in CleanupTransformer later on.
-            node.extra = extra
-            node.type = @program.no_return
-            return
-          else
-            # If the type is not virtual then we know for sure that the type
-            # can't be instantiated, and we can produce a compile-time error.
-            node.raise "Can't pre-initialize abstract class #{instance_type}"
-          end
+          extra = Call.new(
+            nil,
+            "raise",
+            StringLiteral.new("Can't pre-initialize abstract #{base_type.type_desc} #{base_type}"),
+            global: true).at(node)
+          extra.accept self
+
+          # This `extra` will replace the Primitive node in CleanupTransformer later on.
+          node.extra = extra
+          node.type = @program.no_return
+          return false
+        else
+          # If the type is not virtual then we know for sure that the type
+          # can't be instantiated, and we can produce a compile-time error.
+          instance_type = instance_type.devirtualize
+          node.raise "Can't pre-initialize abstract #{instance_type.type_desc} #{instance_type}"
         end
+      end
 
+      if instance_type.struct?
+        element_type = @vars["address"].type.as(PointerInstanceType).element_type
+        if element_type.abstract? && element_type.struct?
+          node.raise "Can't pre-initialize struct using pointer to abstract struct"
+        end
+        node.type = @program.nil_type
+      else
         node.type = instance_type
       end
+
+      false
     end
 
     def visit_pointer_malloc(node)

src/primitives.cr

@@ -58,11 +58,12 @@ class Reference
   # overloads. It zeroes the memory, sets up the type ID (necessary for dynamic
   # dispatch), and then runs all inline instance variable initializers.
   #
-  # *address* must point to a suitably aligned buffer of at least
-  # `instance_sizeof(self)` bytes.
+  # *address* must point to a buffer of at least `instance_sizeof(self)` bytes
+  # with an alignment of `instance_alignof(self)` or above. `ReferenceStorage`
+  # fulfils both requirements.
   #
-  # WARNING: This method is unsafe, as it assumes the caller is responsible for
-  # managing the memory at the given *address* manually.
+  # WARNING: The caller is responsible for managing the memory at the given
+  # *address*, in particular if the memory is not garbage-collectable.
   #
   # ```
   # class Foo
@@ -88,7 +89,7 @@ class Reference
   # foo.i # => 123
   # ```
   #
-  # See also: `Reference.unsafe_construct`.
+  # See also: `Reference.unsafe_construct`, `Struct.pre_initialize`.
   @[Experimental("This API is still under development. Join the discussion about custom reference allocation at [#13481](https://github.com/crystal-lang/crystal/issues/13481).")]
   @[Primitive(:pre_initialize)]
   {% if compare_versions(Crystal::VERSION, "1.2.0") >= 0 %}
@@ -106,6 +107,50 @@ class Reference
   {% end %}
 end
 
+struct Struct
+  # Performs basic initialization so that the given *address* is ready for use
+  # as an object's instance data.
+  #
+  # More specifically, this is the part of object initialization that occurs
+  # after memory allocation and before calling one of the `#initialize`
+  # overloads. It zeroes the memory, and then runs all inline instance variable
+  # initializers.
+  #
+  # *address* must point to a buffer of at least `sizeof(self)` bytes with an
+  # alignment of `alignof(self)` or above. This can for example be a pointer to
+  # an uninitialized instance.
+  #
+  # This method only works for non-virtual constructions. Neither the struct
+  # type nor *address*'s pointee type can be an abstract struct.
+  #
+  # ```
+  # struct Foo
+  #   getter i : Int64
+  #   getter str = "abc"
+  #
+  #   def initialize(@i)
+  #   end
+  # end
+  #
+  # foo = uninitialized Foo
+  # pointerof(foo).to_slice(1).to_unsafe_bytes.fill(0xFF)
+  # Foo.pre_initialize(pointerof(foo))
+  # foo # => Foo(@i=0, @str="abc")
+  # ```
+  #
+  # See also: `Reference.pre_initialize`.
+  @[Experimental("This API is still under development. Join the discussion about custom reference allocation at [#13481](https://github.com/crystal-lang/crystal/issues/13481).")]
+  @[Primitive(:pre_initialize)]
+  {% if compare_versions(Crystal::VERSION, "1.2.0") >= 0 %}
+    def self.pre_initialize(address : Pointer) : Nil
+      \{% @type %}
+    end
+  {% else %}
+    def self.pre_initialize(address : Pointer) : Nil
+    end
+  {% end %}
+end
+
 class Class
   # :nodoc:
   @[Primitive(:class_crystal_instance_type_id)]