Re: Inspirels Ada on cortex tutorial linker issue

[Maciej Sobczak <see.my.homepage@gmail.com>]

> I am able to compile the program from the "First Program" chapter of the tutorial without errors, but when I attempt to link the program I get an error reading:
> 
> program.o:(.ARM.exidx+0x0): undefined reference to '__aeabi_unwind_cpp_pr0'

Sorry for being late to the discussion.
I was able to reproduce this problem and after browsing through some threads on the net, I understand that the newest and greatest gcc compilers automatically add references to exception handling routines even in C code. Apparently there *might* be some obscure integration cases where this automatic injection can help (especially in those projects that mix C and C++), but it is a pity that the "feature" is unconditional. Or at least I was not able to find any option to switch it off.

In any case, I was able to solve the problem by adding the following in any .adb file (for the first program example you can add it to program.adb, but I would recommend moving it to utils.adb or even to some additional file, created only for this purpose):

   procedure Dummy_aeabi_unwind_cpp_pr0;
   pragma Export (C, Dummy_aeabi_unwind_cpp_pr0, "__aeabi_unwind_cpp_pr0");
   
   procedure Dummy_aeabi_unwind_cpp_pr1;
   pragma Export (C, Dummy_aeabi_unwind_cpp_pr1, "__aeabi_unwind_cpp_pr1");
   
   procedure Dummy_aeabi_unwind_cpp_pr0 is
   begin
      null;
   end Dummy_aeabi_unwind_cpp_pr0;
   
   procedure Dummy_aeabi_unwind_cpp_pr1 is
   begin
      null;
   end Dummy_aeabi_unwind_cpp_pr1;

That's it. These procedures will never be called in a pure Ada program, but they make the linker happy. Yes, it'd kind of silly, and I hope that future versions of gcc will have a nice option to switch this nuisance off.

> The linker command I am using is:
> 
> ld -T flash.ld -o program.elf program.o

This command will still work if you put the code above in program.adb, for example after the Run procedure.

-- 
Maciej Sobczak * http://www.inspirel.com