👀 Views: 174 💬 Answers: 1 📅 Created: 2025-06-02

cpp20 allocator vector cpp

I've been banging my head against this for hours. I'm relatively new to this, so bear with me. I am working with an scenario with `std::vector` that seems to involve my custom allocator in C++20. When adding elements to the vector, I encounter data corruption after a reallocation. My custom allocator is based on `std::allocator`, and I am using it like this: ```cpp #include <vector> #include <memory> template <typename T> struct CustomAllocator : std::allocator<T> { T* allocate(std::size_t n) { std::cout << "Allocating " << n << " objects." << std::endl; return std::allocator<T>::allocate(n); } void deallocate(T* p, std::size_t n) { std::cout << "Deallocating " << n << " objects." << std::endl; std::allocator<T>::deallocate(p, n); } }; int main() { std::vector<int, CustomAllocator<int>> vec; for (int i = 0; i < 10; ++i) { vec.push_back(i); } // This should trigger a reallocation for (int i = 10; i < 20; ++i) { vec.push_back(i); } return 0; } ``` However, after the second loop, when I try to access elements of `vec`, I sometimes get garbage values, or worse, a segmentation fault. I’ve ensured that the allocator properly handles allocation and deallocation, and the output indicates that the allocations and deallocations are being logged correctly. I’ve also tried running the code with and without the custom allocator, and the question only occurs with it. Is there any specific pattern or requirement in C++20 regarding custom allocators that I might be missing? Any insight into what might be causing this data corruption would be greatly appreciated! I'm working on a web app that needs to handle this. Any ideas what could be causing this? How would you solve this?