function memory leak

function.cpp

#include <pthread.h>

template <typename... Args> struct function {
    void (*callable)(void *, Args...) = nullptr;
    static constexpr u32 MAX_CONTEXT_SIZE = 32;
    char *context = nullptr;

    function() : context(new char[MAX_CONTEXT_SIZE]) {}

    template <typename Type> function(Type _function) : function() {
        *this = std::move(_function);
    }

    template <typename Type> function &operator=(Type _function) {
        struct Context {
            Type function;
            Context(Type function) : function(std::move(function)) {}
            void invoke(Args... args) {
                function(args...);
            }
        };

        static_assert(sizeof(Context) <= MAX_CONTEXT_SIZE, "context size is too small");

        new (context) Context(std::move(_function));

        callable = [](void *_context, Args... args) {
            static_cast<Context *>(_context)->invoke(args...);
        };

        return *this;
    }

    ~function() = default;

    void operator()(Args... args) {
        if (callable) {
            callable((void *)context, args...);
        }
    }
};

struct thread {
    void *handle = nullptr;
    function<> task;

    thread(function<> &&task) : task(std::move(task)) {
    #if _WIN64
        handle = CreateThread(
            nullptr, 0, (LPTHREAD_START_ROUTINE)task.callable, (void *)task.context, 0, nullptr
        );
    #else
        handle = malloc(sizeof(pthread_t));
        pthread_create(
            (pthread_t *)handle, nullptr, (void *(*)(void *))task.callable, (void *)task.context
        );
    #endif
    }

    ~thread() {
        detach();
    }

    void join() {
        if (!handle) return;
    #if _WIN64
        WaitForSingleObject(handle, INFINITE);
    #else
        pthread_join(*(pthread_t *)handle, NULL);
    #endif
        detach();
    }

    void detach() {
        if (!handle) return;
    #if _WIN64
        CloseHandle(handle);
    #else
        pthread_detach(*(pthread_t *)handle);
        free(handle);
    #endif
        handle = nullptr;
    }
};

// Usage examples
void main() {
    thread audio_loop([]() {
        while (!input.exit) {
            music.update();
        }
    });

    // game loop goes here

    audio_loop.join();
}

void Level::async_save() {
    thread([&]() { save(); }).detach();
}

// If I add a destructor to function
~function() {
    if (context) {
        delete[] context;
    }
}

// I get this error
/*
thread main_font_load([&]() { main_font.load("source_code_pro_regular.ttf"); });
thread emoji_font_load([&]() { emoji_font.load("noto_emoji_regular.ttf"); });
thread japanese_font_load([&]() { japanese_font.load("noto_sans_jp_regular.ttf"); });

main_font_load.join();
emoji_font_load.join();
japanese_font_load.join();
=================================================================
==80797==ERROR: AddressSanitizer: attempting double-free on 0x00013863ad20 in thread T5:
    #0 0x125175c88 in wrap__ZdaPv+0x74 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x61c88)
    #1 0x1046e976c in thread::~thread() base.cpp:292
    #2 0x1047de7a0 in Fonts::load() font.cpp:127
    #3 0x19d37ef90 in _pthread_start+0x84 (libsystem_pthread.dylib:arm64e+0x6f90)
    #4 0x19d379d30 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d30)

0x00013863ad20 is located 0 bytes inside of 32-byte region [0x00013863ad20,0x00013863ad40)
freed by thread T5 here:
    #0 0x125175c88 in wrap__ZdaPv+0x74 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x61c88)
    #1 0x1047de778 in Fonts::load() font.cpp:123
    #2 0x19d37ef90 in _pthread_start+0x84 (libsystem_pthread.dylib:arm64e+0x6f90)
    #3 0x19d379d30 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d30)

previously allocated by thread T5 here:
    #0 0x125175874 in wrap__Znam+0x74 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x61874)
    #1 0x1047de700 in Fonts::load() font.cpp:123
    #2 0x19d37ef90 in _pthread_start+0x84 (libsystem_pthread.dylib:arm64e+0x6f90)
    #3 0x19d379d30 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d30)

Thread T5 created by T0 here:
    #0 0x12515fd6c in wrap_pthread_create+0x54 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x4bd6c)
    #1 0x1046e950c in thread::thread(function<>&&) base.cpp:279
    #2 0x10499c7a4 in main main.cpp:72
    #3 0x19cff60dc  (<unknown module>)

SUMMARY: AddressSanitizer: double-free (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x61c88) in wrap__ZdaPv+0x74
==80797==ABORTING
*/