👀 Views: 67 💬 Answers: 1 📅 Created: 2025-06-10

c++ stdvector customallocator C++

I'm prototyping a solution and I'm sure I'm missing something obvious here, but I'm stuck on something that should probably be simple... I'm encountering a segmentation fault when using `std::vector` with a custom allocator in my C++ project. My custom allocator is based on `std::allocator`, but I have added some tracking to measure allocations. Here's the relevant code for the allocator: ```cpp #include <memory> #include <iostream> template <typename T> class TrackingAllocator { public: using value_type = T; TrackingAllocator() = default; template <typename U> TrackingAllocator(const TrackingAllocator<U>&) {} T* allocate(std::size_t n) { std::cout << "Allocating " << n << " element(s) of size " << sizeof(T) << "\n"; return static_cast<T*>(::operator new(n * sizeof(T))); } void deallocate(T* p, std::size_t) { std::cout << "Deallocating\n"; ::operator delete(p); } }; template <typename T, typename U> bool operator==(const TrackingAllocator<T>&, const TrackingAllocator<U>&) { return true; } template <typename T, typename U> bool operator!=(const TrackingAllocator<T>&, const TrackingAllocator<U>&) { return false; } ``` In my main function, I instantiate a `std::vector` using this custom allocator like this: ```cpp int main() { std::vector<int, TrackingAllocator<int>> myVector; myVector.reserve(10); for (int i = 0; i < 10; ++i) { myVector.push_back(i); } return 0; } ``` When I run this code, I get a segmentation fault, but only when the vector exceeds its initial capacity. I've verified that the allocator is correctly allocating and deallocating memory. I also suspect it might be related to the fact that I'm using a non-throwing `new` operator, as indicated by my `TrackingAllocator`. I've tried enabling and disabling exception handling, but the issue persists. I also checked for any potential memory corruption elsewhere in the code, but nothing seems to stand out. The segmentation fault occurs at the `push_back` when it tries to resize the vector. Any insights on what might be causing this issue with the custom allocator? Is there something specific in the STL's expectations for allocators that I’m missing? This is part of a larger service I'm building. What's the best practice here? My development environment is macOS. I'm developing on Debian with C++. Any examples would be super helpful. I appreciate any insights!