malloc-运行时内存指针类型分配

Question

I don't know how to use malloc correctly when I need my code to determine it's type at runtime. How do I declare one buffer in my header that can use either one of two different structs using malloc during runtime?

struct rgb_16 {
    unsigned short r;
    unsigned short g;
    unsigned short b;
};

struct half_16 {
    half r;
    half g;
    half b;
};

(void*)buffer;

if(sample_format == 1) {
    buffer = (rgb_16*)malloc(width * height * sizeof(rgb_16));
}

if(sample_format == 3) {
    buffer = (half_16*)malloc(width * height * sizeof(half_16));
}

if(tiff.sample_format == 3) {
    // data is float. do not normalize
    for(int x = 0; x < rgba.size(); x++) {
        rgba[x].r = (half)tiff.buffer[x]
                        .r; // error: Subscript of pointer to incomplete type 'void'
        rgba[x].g = (half)tiff.buffer[x]
                        .g; // error: Subscript of pointer to incomplete type 'void'
        rgba[x].b = (half)tiff.buffer[x]
                        .b; // error: Subscript of pointer to incomplete type 'void'

        rgba[x].a = 1.0;
    }
}

I am getting an error that reads:
//error: Subscript of pointer to incomplete type 'void'

I was hoping that by using a void pointer it wouldn't care what type I end up using with malloc for my buffer.

Is there a way to let buffer be filled with either rgb_16 or half_16 at runtime?

First time posting here so please let me know if I should be formatting my post in a different way. Thank you.

Answer 1

Right after if( tiff.sample_format == 3) { , you need something like half_16* h = (half_16*) buffer . The compiler has no way to know what type buffer is, and so has no idea how far to go to get to the x 'th entry. But with h[x] , it does since h is of type half_16* .