Comment by uecker

> How do you make a shallow copy of an object in C++

Shallow copies aren't generally possible for classes storing something indirectly, since it violates ownership semantics. That's not how things are done in C++.. Operator = is usually used for making copies, which is optimized to memcpy for POD structures, but for something more complex may perform extra work for doing an actual deep copy.

> How do you create a stable ABI in C++

It's a complex topic. Basic ABI for calling functions is identical to C. But one need to keep in mind, that type layouts and internal implementations of library types (like containers) may differ from implementation to implementation and from version to version.

> knowing that all my exported functions will mostly just work and be stable as long as I don’t change the interface

Nothing prevents you doing this in C++. You can have C-style external interface and use all goods of C++ internally.

You can’t necessarily do that in C either, it depends on if your object is in a container that relies on pointer stability. Intrusive linked lists are common in C and they get broken by this, for example.

Calling memcpy on any random old struct in C is how you get bugs. If the struct contains other pointers: who is in charge of freeing them? What if the struct has internal pointers (a pointer pointing to a subobject of the struct)? You are playing with fire and you know it.

As if C programmers don’t have to be disciplined. Look if you are a C programmer you need to pick good parts of the language to write in as well. A beginner picked gets()? Oh the foes of the young and inexperienced. You picked VLA? Linus would breathe fire unto you.

A difference between C++ programmers and C programmers is that C++ programmers have the awareness to know their language has bad parts to avoid, but C programmers are oblivious to the bad parts until someone uses it, but otherwise sing paeans for the language.

In C, assigning the return value from malloc() to a specific type merely produces a warning:

  $ echo -ne "#include <stdlib.h>\nint foo() { return malloc(42); }" | gcc -xc -fsyntax-only -c -
  <stdin>: In function ‘foo’:
  <stdin>:2:20: warning: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast [-Wint-conversion]

Whereas in C++ it's a hard error:

  $ echo -ne "#include <stdlib.h>\nint foo() { return malloc(42); }" | gcc -xc++ -fsyntax-only -c -
  <stdin>: In function ‘int foo()’:
  <stdin>:2:26: error: invalid conversion from ‘void*’ to ‘int’ [-fpermissive]

Does this not count as "more type safe" to you?