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Objective-C++ (Wasm)

Objective-C++ is the combination of Objective-C and C++ in a single translation unit, allowing C++ classes and Objective-C messaging to be used together.

In LiveCodes, Objective-C++ runs in the browser using Clang compiled to WebAssembly, with GNUstep's libobjc2 as the Objective-C runtime.

Usage​

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "config": {
    "activeEditor": "script",
    "script": {
      "language": "objcpp-wasm",
      "content": "#import <objc/runtime.h>\n\n#include <iostream>\n#include <string>\nusing namespace std;\n\n__attribute__((objc_root_class))\n@interface Greeter {\n    Class isa;\n}\n- (void)greet:(string)name;\n@end\n\n@implementation Greeter\n- (void)greet:(string)name {\n    cout << \"Hello, \" + name + \"!\" << endl;\n}\n@end\n\nint main() {\n    Greeter *greeter = class_createInstance(objc_getClass(\"Greeter\"), 0);\n    [greeter greet:string(\"World\")];\n    return 0;\n}"
    },
    "mode": "simple",
    "editor": "auto",
    "tools": {
      "status": "full"
    }
  }
};
createPlayground('#container', options);

Communication with JavaScript​

The Objective-C++ code runs in the context of the result page. A few helper properties and methods are available in the browser global livecodes.objcpp object:

  • livecodes.objcpp.input: The initial standard input passed to the code.
  • livecodes.objcpp.loaded: A promise that resolves when the environment is fully loaded. Other helpers should be used after this promise resolves.
  • livecodes.objcpp.output: The standard output from the code execution.
  • livecodes.objcpp.error: The compiler diagnostics, if the code failed to compile.
  • livecodes.objcpp.exitCode: The exit code of the program.
  • livecodes.objcpp.run: A function that compiles and runs the code with new input. This function takes a string as input and returns a promise that resolves with an object containing the output, error and exitCode properties.

The same API is available as livecodes.clangWasm for all Clang-based languages.

Language Info​

Name​

objcpp-wasm

Aliases / Extensions​

mm, objcpp, objcpp-wasm, objc++, objective-c++, wasm.mm, clang.mm, clang-objcpp

Editor​

script

Compiler​

Clang compiled to WebAssembly via @live-codes/clang-wasm, with a complete libc++.

Version​

Clang v22.1.8. The standards gnu++11, gnu++14, gnu++17, gnu++20 and gnu++23 are supported (default: gnu++23).

Limitations​

The Objective-C runtime is GNUstep's libobjc2, which is a runtime and not a class library. There is no NSObject and no NSString, and Foundation is not available. Programs declare their own root class (as in the example above) and create instances directly.

Objective-C exceptions (@try/@catch/@throw) are not supported.

Custom Settings​

The Clang compiler can be configured using custom settings added to the property objcpp-wasm:

PropertyTypeDescription
stdstringThe Objective-C++ standard to compile with: gnu++11, gnu++14, gnu++17, gnu++20 or gnu++23. Defaults to gnu++23.
compileArgsstring[]Extra clang flags, e.g. ["-Wall", "-O2"].
argsstring[]Command-line arguments passed to the program (argv).
Custom Settings
{
  "objcpp-wasm": {
    "std": "gnu++20",
    "compileArgs": ["-Wall", "-O2"],
    "args": ["--name", "LiveCodes"]
  }
}

Code Formatting​

Using @wasm-fmt/clang-format, applying Google's C++ style guide.

Live Reload​

By default, new code changes are sent to the result page without a full page reload, avoiding the need to re-download the compiler. This behavior can be disabled by adding the code comment // __livecodes_reload__ to the code, which forces a full page reload.

This comment can be added in the hiddenContent property of the editor for embedded playgrounds.

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