Strange memory allocation issues?

Dariusz

Hey

A bit confused here :- )
QT6.5

I have as my test utils >

std::atomic<size_t> allocations = 0;

std::atomic<size_t> deallocations = 0;

std::atomic<size_t> badAllocs = 0;

std::atomic<int64_t> totalSizeAllocated;


std::atomic<int64_t> totalBadAllocs;

int64_t total = 0;

std::atomic<bool> mRecordData = true;


void *operator new(std::size_t size) {
    if (mRecordData) {
        allocations++;
        total++;
        void *p = std::malloc(size);
        if (!p) {
            badAllocs++;
            totalBadAllocs += size;
            return p;
        }
        totalSizeAllocated += size;
        return p;
    } else {
        void *p = std::malloc(size);
        return p;
    }
}

void operator delete(void *p) noexcept {
    if (mRecordData) {
        deallocations++;
        total--;
    }
    std::free(p);
}
void startAllocation() {
    allocations = 0;
    deallocations = 0;
    total = 0;
    badAllocs = 0;
    totalSizeAllocated = 0;
    mRecordData = true;
}


void endAllocations() {
    mRecordData = false;
    EXPECT_EQ(allocations, deallocations);
    EXPECT_EQ(total, 0);
    std::cout << "Total Size Allocated: " << totalSizeAllocated << std::endl;
    if (badAllocs) {
        std::cout << "BAD ALLOCS !!! : " << badAllocs << " ||| " << totalBadAllocs << std::endl;
    }
}

And as test I have >

    startAllocation();
    {
        QString s = "csacsa";
        auto s2 = std::string("Hello");
        auto sutf = s.toUtf8();
        auto s3 = sutf.toStdString(); // memory leak???
        auto s4 = s.toStdString(); // memory leak???
    }
    endAllocations();

testLog

  allocations
    Which is: 1
  deallocations
    Which is: 3
  total
    Which is: -2
  0
Total Size Allocated: 16

Any idea why converting QString to stdString causes memory allocation issues?

Edit1
Strange enough if I do this >
auto ah = std::string{sutf.data(), (unsigned __int64) sutf.size()};
auto ah2 = std::string{s2 .toUtf8().data(), (unsigned __int64) s2.size()};
no allocations issues? O.O

Christian Ehrlicher

@Dariusz said in Strange memory allocation issues?:

Any idea why converting QString to stdString causes memory allocation issues?

I don't know what you're trying to achieve - if you want to look for memory leaks use the appropriate tools but those two functions don't leak any memory.

/edit:
and btw: there is more than one new operator: https://en.cppreference.com/w/cpp/memory/new/operator_new

Dariusz

@Christian-Ehrlicher Oh snap. So I have to wrapp all of new allocators/deallocators to properly track it. Ahhhhhhhh my bad, off to add more !
Thanks for ping!
Will be back after further testing.

Dariusz

@Christian-Ehrlicher said in Strange memory allocation issues?:

@Dariusz said in Strange memory allocation issues?:

Any idea why converting QString to stdString causes memory allocation issues?

I don't know what you're trying to achieve - if you want to look for memory leaks use the appropriate tools but those two functions don't leak any memory.

/edit:
and btw: there is more than one new operator: https://en.cppreference.com/w/cpp/memory/new/operator_new

Meh no luck, added other ones but failed to track it :/

// 1. Simple allocation
void *operator new(std::size_t size) {
    if (mRecordData) {
        allocations++;
        total++;
        void *p = std::malloc(size);
        if (!p) {
            badAllocs++;
            totalBadAllocs += size;
            throw std::bad_alloc();
        }
        totalSizeAllocated += size;
        return p;
    }
    return std::malloc(size);
}

// 2. Array allocation
void *operator new[](std::size_t size) {
    return ::operator new(size);
}

// 3. No-exception allocation
void *operator new(std::size_t size, const std::nothrow_t &) noexcept {
    if (mRecordData) {
        allocations++;
        total++;
        void *p = std::malloc(size);
        if (!p) {
            badAllocs++;
            totalBadAllocs += size;
        }
        return p;
    }
    return std::malloc(size);
}

// 4. Array no-exception allocation
void *operator new[](std::size_t size, const std::nothrow_t &nt) noexcept {
    return ::operator new(size, nt);
}

#if __cplusplus >= 201703L
// 5. Aligned allocation (C++17 onward)
void *operator new(std::size_t size, std::align_val_t al) {
    if (mRecordData) {
        allocations++;
        total++;
        void *p = _aligned_malloc(static_cast<size_t>(al), size);
        if (!p) {
            badAllocs++;
            totalBadAllocs += size;
            throw std::bad_alloc();
        }
        totalSizeAllocated += size;
        return p;
    }
    return _aligned_malloc(static_cast<size_t>(al), size);
}

// 6. Aligned array allocation (C++17 onward)
void *operator new[](std::size_t size, std::align_val_t al) {
    return ::operator new(size, al);
}
#endif

// Corresponding delete overloads
void operator delete(void *p) noexcept {
    if (mRecordData) {
        deallocations++;
        total--;
    }
    std::free(p);
}

void operator delete[](void *p) noexcept {
    ::operator delete(p);
}

void operator delete(void *p, const std::nothrow_t &) noexcept {
    ::operator delete(p);
}

void operator delete[](void *p, const std::nothrow_t &) noexcept {
    ::operator delete(p);
}

#if __cplusplus >= 201703L
void operator delete(void *p, std::align_val_t) noexcept {
    ::operator delete(p);
}

void operator delete[](void *p, std::align_val_t) noexcept {
    ::operator delete(p);
}
#endif

Bummer!

Just wanted a lightweight way of tracking my test allocations/memory footpring :c
I know there is valgrind/other ones, but they are harder to set up for per-function tests/etc inside gtest as far as I can tell :/