std::vector with custom allocator causing segmentation fault in C++20
I'm optimizing some code but I need some guidance on I've been banging my head against this for hours... I'm experiencing a segmentation fault when using a custom allocator with `std::vector`. I've implemented an allocator that tracks memory allocations, but when I try to create a vector of a certain type, the program crashes. Here’s a minimal example of my allocator and vector initialization: ```cpp #include <iostream> #include <vector> #include <memory> template <typename T> struct CustomAllocator { using value_type = T; CustomAllocator() = default; template <class U> CustomAllocator(const CustomAllocator<U>&) noexcept {} T* allocate(std::size_t n) { std::cout << "Allocating " << n << " objects." << std::endl; if (auto p = std::malloc(n * sizeof(T))) { return static_cast<T*>(p); } throw std::bad_alloc(); } void deallocate(T* p, std::size_t) noexcept { std::cout << "Deallocating." << std::endl; std::free(p); } }; int main() { std::vector<int, CustomAllocator<int>> vec; vec.reserve(10); // This line causes the segmentation fault. return 0; } ``` When I run this code, I get a segmentation fault on the `vec.reserve(10);` line. I suspect it might be related to how `std::vector` interacts with the allocator or how the memory is being allocated. I’ve ensured that my allocator adheres to the requirements, including the default constructor and copy constructor. I've tried adding debug logs in the allocator's `allocate` and `deallocate` methods, and they seem to execute correctly without any exceptions being thrown. Also, I've checked that the size of `T` is appropriate when allocating. Could there be something I'm overlooking in the allocator's design? Is there a specific requirement for allocators in C++20 that I might have missed? Any insights would be greatly appreciated! My development environment is macOS. Am I missing something obvious? I'm open to any suggestions. What would be the recommended way to handle this?