In ARC, C++ std::vector has Objective-C instances

ObjcInCppVector.mm

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

@interface ObjcClass: NSObject
@property (nonatomic, readonly) NSString *name;
- (instancetype)initWithName:(NSString *)name;
- (void)speak;
@end

@implementation ObjcClass
- (instancetype)initWithName:(NSString *)name {
    self = [super init];
    if (self) {
        _name = name;
    }
    return self;
}
- (void)dealloc { NSLog(@"%@ is deleted", self.name); }
- (void)speak { NSLog(@"I am %@", self.name); }
@end

class CppClass {
public:
    std::vector<ObjcClass*> m_objcInstances;    // ### Is ARC enabled? ###
public:
    CppClass()
    : m_objcInstances() {
        for (int i = 0; i < 5; ++i) {
            auto name = [NSString stringWithFormat:@"Objc instance %d", i];
            m_objcInstances.push_back([[ObjcClass alloc] initWithName:name]);
        }
    }
    ~CppClass() { NSLog(@"CppClass is deleted"); }
    void Speak() const {
        for (auto objc : m_objcInstances) {
            [objc speak];
        }
    }
};

int main(int argc, const char * argv[]) {
    ObjcClass *reference = nil;
    @autoreleasepool {
        NSLog(@"Hello, World!");
        const auto cppClass = CppClass();
        cppClass.Speak();
        reference = cppClass.m_objcInstances[2];  // retain
    }
    NSLog(@"End");
    return 0;
}

Debug out of Xcode 9.4

2018-06-16 21:41:57.900903+0900 objective_cpp_practice[6036:398272] Hello, World!
2018-06-16 21:41:57.901257+0900 objective_cpp_practice[6036:398272] I am Objc instance 0
2018-06-16 21:41:57.901283+0900 objective_cpp_practice[6036:398272] I am Objc instance 1
2018-06-16 21:41:57.901301+0900 objective_cpp_practice[6036:398272] I am Objc instance 2
2018-06-16 21:41:57.901317+0900 objective_cpp_practice[6036:398272] I am Objc instance 3
2018-06-16 21:41:57.901338+0900 objective_cpp_practice[6036:398272] I am Objc instance 4
2018-06-16 21:41:57.901354+0900 objective_cpp_practice[6036:398272] CppClass is deleted
2018-06-16 21:41:57.901372+0900 objective_cpp_practice[6036:398272] Objc instance 4 is deleted
2018-06-16 21:41:57.901414+0900 objective_cpp_practice[6036:398272] Objc instance 3 is deleted
2018-06-16 21:41:57.901555+0900 objective_cpp_practice[6036:398272] Objc instance 1 is deleted
2018-06-16 21:41:57.901594+0900 objective_cpp_practice[6036:398272] Objc instance 0 is deleted
2018-06-16 21:41:57.901624+0900 objective_cpp_practice[6036:398272] End
2018-06-16 21:41:57.901648+0900 objective_cpp_practice[6036:398272] Objc instance 2 is deleted