test.mm

#import <Foundation/Foundation.h>
#import <vector>

int main()
{
    std::vector<__weak NSObject *> a;

    a.push_back([NSObject new]);
    a.push_back([NSObject new]);
    a.push_back([NSObject new]);

    for (auto& v : a) {
        NSLog(@"%@", v);
    }

    return 0;
}