c++ - How to include data object files (images, etc.) in program and access the symbols?

Question

I've turned a couple of resource files into .obj files using objcopy and i link them with my programs source code. I can very well access the symbols inside the object file in my program with the following code, but only with GCC/G++ (Cygwin):

extern uint8_t data[]   asm("_binary_Resources_0_png_start");
extern uint8_t size[]   asm("_binary_Resources_0_png_size");
extern uint8_t end[]    asm("_binary_Resources_0_png_end");

The code doesn't work in Visual Studio, probably because VS has it's own __asm command. I want to include my programs resources (Images, Shaders, etc.) in my final executable's .data section through linking them.

But how can i access the symbols defined in the object file in VC++? I tried extern uint8_t _binary_Resources_0_png_start[] or extern "C" uint8_t _binary_Resources_0_png_start[] without the assembly command, but i get unresolved symbol link errors.

Answer 1

The trick with objcopy isn't meant as a full-featured way to embed resources and isn't portable at all, as you have seen.

Microsoft has its own mechanism for resources, so if you're specifically targeting windows, you could use a windows resource file and the RCDATA resource.

If you want something completely portable, your only option is to format the file as C sourcecode like e.g.

const uint8_t my_binary[] = { 0x00, 0x01, ... }

It's straight forward to write your own conversion tool for that.