Modify implementation of structs to support unions

This was simple enough, we just needed to change the part where we
were computing the offset for each field, and the total size of the
compound structure.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/types.c b/src/types.c
index 5138164..008af10 100644
--- a/src/types.c
+++ b/src/types.c
@@ -107,6 +107,7 @@ static char *data_type_to_str(Type *type)
     case TYPE_CHAR: return "char";
     case TYPE_ANY: return "<@>";
     case TYPE_STRUCT: return type->struct_name;
+    case TYPE_UNION: return type->struct_name;
     default: assert(false && "Unreachable");
     }
 }
@@ -133,19 +134,21 @@ char *type_to_str(Type *type)
 
 i64 push_field(Type *type, char *field_name, Type *field_type)
 {
-    assert(type->type == TYPE_STRUCT);
+    assert(type->type == TYPE_STRUCT || type->type == TYPE_UNION);
+    bool is_union = type->type == TYPE_UNION;
+
     type->fields.type = realloc(type->fields.type, sizeof(Type *) * (type->fields.num_fields + 1));
     type->fields.offset = realloc(type->fields.offset, sizeof(i64) * (type->fields.num_fields + 1));
     type->fields.name = realloc(type->fields.name, sizeof(char *) * (type->fields.num_fields + 1));
    
     i64 field_size = size_for_type(field_type);
     i64 offset_factor = i64min(field_size, 8);
-    i64 offset = align_up(type->fields.size, offset_factor);
+    i64 offset = is_union ? 0 : align_up(type->fields.size, offset_factor);
      
     type->fields.type[type->fields.num_fields] = field_type;
     type->fields.offset[type->fields.num_fields] = offset;
     type->fields.name[type->fields.num_fields] = field_name;
-    type->fields.size = offset + field_size;
+    type->fields.size = is_union ? i64max(field_size, type->fields.size) : offset + field_size;
     type->fields.num_fields++;
 
     return offset;
@@ -153,7 +156,7 @@ i64 push_field(Type *type, char *field_name, Type *field_type)
 
 i64 find_field_index(Type *type, char *field_name)
 {
-    assert(type->type == TYPE_STRUCT);
+    assert(type->type == TYPE_STRUCT || type->type == TYPE_UNION);
     for (int i = 0; i < type->fields.num_fields; i++) {
         if (strcmp(type->fields.name[i], field_name) == 0)
             return i;