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Newsgroups: comp.lang.ada
Date: Sat, 20 Aug 2016 15:09:24 -0700 (PDT)
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Subject: Re: Inspirels Ada on cortex tutorial linker issue
From: Maciej Sobczak <see.my.homepage@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:31470
Date: 2016-08-20T15:09:24-07:00
List-Id: <comp.lang.ada>

> 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 er=
ror reading:
>=20
> program.o:(.ARM.exidx+0x0): undefined reference to '__aeabi_unwind_cpp_pr=
0'

Sorry for being late to the discussion.
I was able to reproduce this problem and after browsing through some thread=
s on the net, I understand that the newest and greatest gcc compilers autom=
atically add references to exception handling routines even in C code. Appa=
rently 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 abl=
e 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, bu=
t 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");
  =20
   procedure Dummy_aeabi_unwind_cpp_pr1;
   pragma Export (C, Dummy_aeabi_unwind_cpp_pr1, "__aeabi_unwind_cpp_pr1");
  =20
   procedure Dummy_aeabi_unwind_cpp_pr0 is
   begin
      null;
   end Dummy_aeabi_unwind_cpp_pr0;
  =20
   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 futur=
e versions of gcc will have a nice option to switch this nuisance off.

> The linker command I am using is:
>=20
> 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.

--=20
Maciej Sobczak * http://www.inspirel.com