&gt; I would assert that virtually every non-trivial C&#x2F;C++ program<p>First, citation needed.<p>Second, the programs I work on would fall outside of your &quot;virtually every&quot;.<p>&gt; [big list of things]<p>This list doesn&#x27;t prove anything. There&#x27;s a similar list in the standards themselves. That&#x27;s how we know what to avoid.<p>Oh, and we have an in-house static analysis program that catches all of those. And more.<p>Our code simply has no undefined behavior. It passes our static analysis program, it passes UBSAN, and no compiler has ever miscompiled our code (unless it was due to a compiler bug).<p>You can try all you like, but there&#x27;s no way for you to convince me that our code has undefined behavior. And there are plenty of projects out there similar to ours.<p>&gt; if you have any sort of custom memory allocation scheme, you&#x27;re pretty much guaranteed to break this<p>Not true. You should learn about the aliasing rules before you speak authoritatively about them.<p>&gt; Functions like memcpy or malloc cannot legally be written in C without breaking this behavior<p>Also not true.<p>&gt; Your program probably has undefined behavior.<p>The chances of that are much less than the chances of you not knowing what you are talking about.