C++ officially supports a new platform: what this means for developers

C++ now officially supports WASI: a new stage in cross-platform development

The C++ language standardization committee (ISO/IEC JTC1/SC22/WG21), together with the LLVM developer group and the WebAssembly project, have announced a long-awaited event: the C++ language has received official, documented support for the WebAssembly System Interface (WASI) platform. This means that developers can now write system code in C++ that will run not only on traditional operating systems (Windows, Linux, macOS), but also in the WebAssembly environment outside the browser — on servers, IoT devices, and cloud edge systems.

What is WASI and why is it important for C++?

WASI (WebAssembly System Interface) is a standardized system interface that provides WebAssembly modules with access to the file system, network sockets, time, and other operating system resources. Previously, C++ could be compiled to WebAssembly, but interaction with the outside world was limited to the browser environment. Now, with official WASI support, C++ gains a fully isolated environment for secure code execution outside the browser.

• Security: C++ modules run in a sandbox with resource access control — ideal for multi-tenant services.
• Portability: A single .wasm binary file runs on any OS that has a WASI runtime environment (Wasmer, Wasmtime, WAMR).
• Performance: Compiling C++ directly to native WebAssembly code (via Clang/LLVM) delivers near-native execution speed, without the overhead of a virtual machine.

What has changed in the C++ ecosystem?

The main innovation is the release of an official guide for porting C++ code to WASI and the inclusion of WASI support in the main LLVM repository. Now any C++ project can be compiled for WASI using a simple compiler flag:

clang++ --target=wasm32-wasi -O3 my_program.cpp -o my_program.wasm

In addition, the standard C++ libraries (libc++, libc++abi) have been updated for correct operation with WASI system calls. Developers no longer need to manually configure linking with external libraries — everything works "out of the box".

Where is this already being applied?

• Cloud computing: Running C++ microservices in isolated WASI containers (e.g., in Fastly Compute@Edge or Cloudflare Workers with WASI support).
• Embedded systems: Using WASI for secure firmware updates of IoT devices written in C++.
• Scientific computing: Porting computationally intensive C++ modules (linear algebra libraries, simulations) to WASI for cross-platform execution without recompilation.

What's next?

Upcoming plans include full support for C++ multithreading in WASI (currently only a single-threaded model is available) and integration with C++20/23 coroutines. The community is already working on adapting popular libraries (Boost, Qt, OpenCV) for compilation under WASI. Stay tuned for updates on the official website wasi.dev and in the LLVM repository.

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