Fix Issue 18828 - [-betterC] helpless error in object.d

posix.mak

@@ -241,7 +241,7 @@ UT_MODULES:=$(patsubst src/%.d,$(ROOT)/unittest/%,$(SRCS))
 HAS_ADDITIONAL_TESTS:=$(shell test -d test && echo 1)
 ifeq ($(HAS_ADDITIONAL_TESTS),1)
 	ADDITIONAL_TESTS:=test/init_fini test/exceptions test/coverage test/profile test/cycles test/allocations test/typeinfo \
-	    test/thread test/unittest test/imports
+	    test/thread test/unittest test/imports test/betterc
 	ADDITIONAL_TESTS+=$(if $(SHARED),test/shared,)
 endif
 

src/object.d

@@ -3027,14 +3027,19 @@ unittest
 /// ditto
 void destroy(T)(ref T obj) if (is(T == struct))
 {
+    // We need to re-initialize `obj`.  Previously, the code
+    // `auto init = cast(ubyte[])typeid(T).initializer()` was used, but
+    // `typeid` is a runtime call and requires the `TypeInfo` object which is
+    // not usable when compiling with -betterC.  If we do `obj = T.init` then we
+    // end up needlessly calling postblits and destructors.  So, we create a
+    // static immutable lvalue that can be re-used with subsequent calls to `destroy`
+    shared static immutable T init = T.init;
+
     _destructRecurse(obj);
     () @trusted {
-        auto buf = (cast(ubyte*) &obj)[0 .. T.sizeof];
-        auto init = cast(ubyte[])typeid(T).initializer();
-        if (init.ptr is null) // null ptr means initialize to 0s
-            buf[] = 0;
-        else
-            buf[] = init[];
+        auto dest = (cast(ubyte*) &obj)[0 .. T.sizeof];
+        auto src = (cast(ubyte*) &init)[0 .. T.sizeof];
+        dest[] = src[];
     } ();
 }
 

test/betterc/Makefile

@@ -0,0 +1,12 @@
+include ../common.mak
+
+TESTS:=test18828
+
+.PHONY: all clean
+all: $(addprefix $(ROOT)/,$(addsuffix ,$(TESTS)))
+
+$(ROOT)/%: $(SRC)/%.d
+	$(QUIET)$(DMD) -betterC -c -of$@ $<
+
+clean:
+	rm -rf $(ROOT)

test/betterc/src/test18828.d

@@ -0,0 +1,10 @@
+/*******************************************/
+// https://issues.dlang.org/show_bug.cgi?id=18828
+
+struct S18828 { }
+
+void test18828()
+{
+    S18828 s;
+    destroy(s);
+}