Original Post

I want to embed a binary file into a VB rom, and access its data through a pointer in the c source code. So I made a linkable object of the file with ld like so:

$ v810-ld -r -b binary -o myfile.o myfile.bin

Inspecting the results using objdump shows this:

$ v810-objdump -x myfile.o

myfile.o:     file format elf32-v810
architecture: v810, flags 0x00000010:
start address 0x00000000
private flags = 0: v810 architecture

Idx Name          Size      VMA       LMA       File off  Algn
  0 .data         000031de  05000000  05000000  00000034  2**0
                  CONTENTS, ALLOC, LOAD, DATA
05000000 l    d  .data	00000000 
00000000 l    d  *ABS*	00000000 
00000000 l    d  *ABS*	00000000 
00000000 l    d  *ABS*	00000000 
000031de g       *ABS*	00000000 _binary_myfile_bin_size
05000000 g       .data	00000000 _binary_myfile_bin_start
070003ff g       *ABS*	00000000 __vbvectors_end
050031de g       *ABS*	00000000 __data_end
000003ff g       *ABS*	00000000 v
050031de g       .data	00000000 _binary_myfile_bin_end
070001e0 g       *ABS*	00000000 __vbvectors_lma
05000000 g       *ABS*	00000000 __data_vma
00000000 g       *ABS*	00000000 __data_lma
07000000 g       *ABS*	00000000 __text_vma

Then I declare and use the variable in the c source using the symbol names from the object file:

extern const BYTE _binary_myfile_bin_start[];

BYTE abc = _binary_myfile_bin_start[0];

The problem is I’m getting a compiler error saying undefined reference to ‘_binary_myfile_bin_start’. So I guess I’m not linking the object file correctly…

I’m compiling like this:
$ v810-gcc -O -I. *.c *.o -o test.elf

The same line compiles fine if I don’t try to use the symbol within the c code…

Does anyone have an idea how to do this correctly?
(DogP, I’m guessing you must have compiled the GB rom into your GB emulator rom?)

Thanks guys!

3 Replies

Try omitting the leading underscore from the symbol name:

extern const BYTE binary_myfile_bin_start[];

BYTE abc = binary_myfile_bin_start[0];

Awesome, that was all it took! Thanks dasi! 😀

How can I make it so the data isn’t loaded into ram? I want it to stay in the rom and just have my pointer point to it there.

I’ve been trying to put it in the .rodata section of the object file, but the v810 version of objcopy is lacking the –rename-section switch for some reason…


Write a reply

You must be logged in to reply to this topic.