[llvm-dev] bpf compilation using clang

[Tim Northover via llvm-dev]

On Thu, 13 Sep 2018 at 10:58, Sameeh Jubran via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I am not sure how to debug this error since the instructions are in
> binary and the precompiled source code doesn't seem to contain any
> weird loops or goto instructions...
>
> Is there a way to identify which line of source code is causing these errors?

First step would be to look at the assembly and try to work out what
instructions 363 and 364 are. If you add "-S" to the clang
command-line it should get you some assembly. With luck the problem
will be around line "363 + header rubbish" and there will be an
obvious pair of instructions where the earlier one refers to the
result of a later one; with even more luck it'll be easy to map those
instructions back to your source (though it's probably an LLVM bug to
produce them in the first place).

If you send files reproducing the issue here people will have more
information to give you advice.

> and then were translated to bpf instructions using the BPFCparser tool

You seem to be the only person on the internet to have mentioned this
tool. If it's mangling the instruction stream it's also a candidate
for introducing bugs.

Cheers.

Tim.