xo-jit: drop isPacked=true when creating struct types

src/jit/MachPipeline.cpp

@@ -247,9 +247,6 @@ namespace xo {
                 std::string struct_name = std::string(struct_td->short_name());
 
                 /* structs with names:  within an llvmcontext, must be unique
-                 *
-                 * If we don't set isPacked,  then padding will be chosen based on DataLayout,
-                 * which might C++ compiler's padding,  but no guarantees.
                  *
                  * We can however compare the offsets recorded in xo::reflect with
                  * offsets chosen by llvm, *once we've created the llvm type*
@@ -268,7 +265,7 @@ namespace xo {
                     = llvm::StructType::create(llvm_cx_ref,
                                                llvm_membertype_v,
                                                llvm::StringRef(struct_name),
-                                               true /*isPacked*/);
+                                               false /*!isPacked*/);
 
                 /* TODO: inspect (how) offsets that llvm is using
                  * we need them to match what C++ chose