Accessing a C++ Object in C Code

C code, which of course is unaware of object semantics, can access the data members of a C++ object directly, but certain requirements must be met. There are some guarantees about the underlying memory layout of an object. C code can take advantage of these guarantees and treat a C++ object as an ordinary data struct, provided that all the following restrictions apply to the class of the object in question:

  • The class has no virtual member functions (including inherited virtual functions of a base class).
  • The class has no virtual base classes in the entire inheritance chain.
  • The class has no member objects that have either a virtual base class or virtual member functions.
  • All the data members of the class are declared without an intervening access specifier.

The compatible memory layout of C++ objects and C structs has many useful applications. For example, it enables relational databases to retrieve and insert objects into a database table. Data Manipulation Languages, such as SQL, that do not support object semantics, can still treat a “live” object as a raw chunk of memory. In fact, several commercial databases rely on this compatibility to provide an object-oriented interface with an underlying relational data model. Another application is the capability to transmit objects as a stream of bytes from one machine to another.

Share the Post:
Share on facebook
Share on twitter
Share on linkedin

Overview

The Latest

iOS app development

The Future of iOS App Development: Trends to Watch

When it launched in 2008, the Apple App Store only had 500 apps available. By the first quarter of 2022, the store had about 2.18 million iOS-exclusive apps. Average monthly app releases for the platform reached 34,000 in the first half of 2022, indicating rapid growth in iOS app development.

microsoft careers

Top Careers at Microsoft

Microsoft has gained its position as one of the top companies in the world, and Microsoft careers are flourishing. This multinational company is efficiently developing popular software and computers with other consumer electronics. It is a dream come true for so many people to acquire a high paid, high-prestige job

your company's audio

4 Areas of Your Company Where Your Audio Really Matters

Your company probably relies on audio more than you realize. Whether you’re creating a spoken text message to a colleague or giving a speech, you want your audio to shine. Otherwise, you could cause avoidable friction points and potentially hurt your brand reputation. For example, let’s say you create a