Pass `const void*` to C++ binded function

[haylinmoore]

Hello,

I'm trying to create Rust bindings for the library for the library https://github.com/richgel999/fpng, I'm trying to bind against their function with a signature of

  bool fpng_encode_image_to_memory(const void* pImage, uint32_t w, uint32_t h, uint32_t num_chans, std::vector<uint8_t>& out_buf, uint32_t flags = 0);

So far I have

        unsafe fn fpng_encode_image_to_memory(pImage: *const i32, width: u32, height: u32, num_chans: u32, out_buf: &CxxVector<u8>, flags: u32) -> bool;

Which according to cxx has the signature of bool (*)(const int*, unsigned int, unsigned int, unsigned int, const std::vector<unsigned char>&, unsigned int) while the intended signature would be bool (*)(const void*, unsigned int, unsigned int, unsigned int, std::vector<unsigned char>&, unsigned int)

How do I inform cxx I would like to pass a void pointer to some data? I tried a lot related to passing [u8]s, but could never get it working

Thank you

[Louis-Simon22]

I would also like to know how to do this

[dtolnay]

There isn't yet a void binding built in, but it's easy to DIY. In your header add:

using c_void = void;

and then in your extern "C++" module:

    type c_void;
    unsafe fn fpng_encode_image_to_memory(pImage: *const c_void, width: u32, …);