Safe C++: A Revolutionary Extension Proposal for Memory Safety in C++

The C++ community has announced a "Safe C++" extension proposal that aims to add memory‑safety features to the language.

The proposal is being developed by the C++ Alliance together with engineer Sean Baxter, and the Alliance plans to submit it to ISO for inclusion in the C++ standard.

C++ Alliance is a nonprofit organization dedicated to making the C++ language more accessible and useful, with a mission to help anyone learn and apply C++.

Example code written with the Safe C++ extension demonstrates the new safety syntax:

#feature on safety
#include
int main() safe {
  std2::vector
vec { 11, 15, 20 };
  for (int x : vec) {
    // Ill‑formed. mutate of vec invalidates iterator in ranged‑for.
    if (x % 2)
      mut vec.push_back(x);
    std2::println(x);
  }
}

The compiler’s safety checker produces diagnostics such as:

$ circle iterator.cxx -I ../libsafecxx/single-header/
safety: during safety checking of int main() safe
  borrow checking: iterator.cxx:10:11
    mut vec.push_back(x);
    ^
  mutable borrow of vec between its shared borrow and its use
  loan created at iterator.cxx:7:15
    for(int x : vec) {
                ^

Vinnie Falco, chair and CEO of the C++ Alliance, wrote that this partnership marks a milestone in the C++ ecosystem because the need for secure code has never been more urgent.

The "Safe C++" extension introduces a "Safe Standard Library" that provides robust, memory‑safe implementations of fundamental data structures and algorithms, preserving C++’s performance and flexibility.

In the broader context, major tech companies have highlighted memory‑safety vulnerabilities, and U.S. agencies such as the White House, CISA, NSA, and DARPA have promoted memory‑safe languages like Rust; even Bjarne Stroustrup has noted that perfect type and memory safety can now be achieved in ISO C++.

References: https://www.theregister.com/2024/09/16/safe_c_plusplus/ https://safecpp.org/P3390R0.html https://cppalliance.org/vinnie/2024/09/12/Safe-Cpp-Partnership.html