On Thu, 22 Oct 2020 at 06:02, Helmut Zeisel <HZ2012@xxxxxx> wrote: > > According to https://en.cppreference.com/w/cpp/compiler_support > GCC does not yet support "Extending std::make_shared() to support arrays" > Anyway, the following code > > #include <memory> > #include <iostream> > template<typename T> int test() > { > std::shared_ptr<T[]> p1 = std::make_shared<T[]>(2); > std::shared_ptr<T[]> p2 = p1; > p2[1] = 5; > std::cout << p1[1] << std::endl; > return 0; > } > int main() > { > test<int>(); > std::cout << "Done int" << std::endl; > test<long>(); > std::cout << "Done long" << std::endl; > } > > compiles ad gives the expected result on Linux and when using the compiler explorer https://godbolt.org/ for GCC 10.2: > > 5 > Done int > 5 > Done long It actually creates a shared_ptr<long> with a single element and then p[1] is undefined behaviour. Valgrind shows the code is wrong even on linux, it just doesn't crash in compiler explorer. > Using GCC 10.2 on cygwin64, however, it crashes: > > 5 > Done int > 5 > Aborted (core dumped) > > Maybe this is somehow related to alignment (it also crashes for double). > Is this a bug in GCC or a bug in cygwin? Or is it actually no bug because this feature is not yet supported? The feature is not yet supported.
