Re: [Caml-list] <DKIM> Application crashing when build with cross-compiler

[Xavier Leroy <Xavier.Leroy@inria.fr>]

On 14/10/15 14:29, Stefan Hellermann wrote:
> I tried to reproduce this on a x86_32 cross-compiled target, but failed. I
> tried to create exactly the same environment for x86_32, same libc, same
> compiler, same kernel. Only difference to compiling for my target is
> endianess, mips is big endian and x86_32 is little endian.

Well, MIPS can also run in little-endian ("mipsel" in Debian speak),
but I'm assuming you run a big-endian MIPS kernel.

I see Debian has a Unison package for mips and other big-endian
platforms, which I presume works, so it's not an endianness dependency
in Unison itself nor in the OCaml libraries that Unison depends on.

> Is there anything else I can try?

You could build the OCaml runtime in debug mode:

cd /path/to/ocaml/sources/byterun && make ocamlrund

Then use it to run Unison:

/path/to/ocaml/sources/byterun/ocamlrund unison file1 file2

ocamlrund is compiled without C optimizations and with a lot of
internal checks, so it could help find possible problems with your
cross C compiler or target C library.

> Can someone point me to a few test scripts
> which I could run on the mips target and see if something fails?

There's always the testsuite/ part of the OCaml source distribution,
which you could run either on the target or on the host through qemu.

cd /path/to/ocaml/sources/testsuite && make BYTECODE_ONLY=true all

Adrien Nader adds:

> Hmmmm, endianess is indeed likely to cause troubles.

I'm skeptical.  Wrong endianness in config/m.h would cause ocamlrun to
crash immediately.

> Do the cross-build from x86_64 to ix86  (or the other way round) and
> look for warnings from as (need the end of the build iirc). 

The original poster is using bytecode, as native-code generation is
not available for MIPS anyway.

- Xavier Leroy