Lambda mangling test

[kassane]

Some lambda test - C++20: https://godbolt.org/z/Gq1h7Ezn9

Lambda 1

input

#include <iostream>
template<typename T> int print_hello = (std::cout << "hello\n", 0);
struct X {
  // Should only print hello once, regardless of how many TUs this appears in.
  static const intptr_t n = (print_hello<decltype([]{})>, 0);
};

output

error: unhandled `VarTemplateDecl`
error: unhandled `VarTemplateSpecializationDecl`
info: transpiled 214903/214939 (99.98 %)
info: formating `x86_64/linux/gnu/cxx.zig`

// auto generated by c2z
const std = @import("std");
//const cpp = @import("cpp");

pub const X = extern struct {
    extern const _ZN1X1nE: isize;
    pub inline fn n() isize {
        return _ZN1X1nE;
    }
};

Lambda 2

input

struct A {
  int f(decltype([]{ static int n; return ++n; }) lambda = {}) {
    return lambda();
  }
};
int a = A().f(), b = A().f();

output

info: binding `cxx.h`
error: unknow type `decltype([] {
    static int n;
    return ++n;
})`, falling back to `*anyopaque`
error: unhandled `RecoveryExpr`
error: syntax errors in `A.f`
info: transpiled 56/58 (96.55 %)
info: formating `x86_64/linux/gnu/cxx.zig`

// auto generated by c2z
const std = @import("std");
//const cpp = @import("cpp");

pub const A = extern struct {

    // syntax errors:
    // pub fn f(self: *A, lambda: *anyopaque) c_int {
    // return ();
    // }
    //
};

extern var a: c_int;
pub inline fn a() *c_int {
    return &a;
}

extern var b: c_int;
pub inline fn b() *c_int {
    return &b;
}

References

• https://github.com/itanium-cxx-abi/cxx-abi/issues/157#issuecomment-1611955848
• https://github.com/itanium-cxx-abi/cxx-abi/issues/31#issuecomment-529712699