Re: [patch] PR jit/87808: Allow libgccjit to work without an external gcc driver

[Matthias Klose <doko@ubuntu.com>]

On 7/13/21 8:41 AM, Richard Biener wrote:
> On Mon, Jul 12, 2021 at 11:00 PM Matthias Klose <doko@ubuntu.com> wrote:
>>
>> On 3/26/19 12:52 PM, Matthias Klose wrote:
>>> On 22.03.19 23:00, David Malcolm wrote:
>>>> On Thu, 2019-03-21 at 12:26 +0100, Matthias Klose wrote:
>>>>> Fix PR jit/87808, the embedded driver still needing the external gcc
>>>>> driver to
>>>>> find the gcc_lib_dir. This can happen in a packaging context when
>>>>> libgccjit
>>>>> doesn't depend on the gcc package, but just on binutils and libgcc-
>>>>> dev packages.
>>>>> libgccjit probably could use /proc/self/maps to find the gcc_lib_dir,
>>>>> but that
>>>>> doesn't seem to be very portable.
>>>>>
>>>>> Ok for the trunk and the branches?
>>>>>
>>>>> Matthias
>>>>
>>>> [CCing the jit list]
>>>>
>>>> I've been trying to reproduce this bug in a working copy, and failing.
>>>>
>>>> Matthias, do you have a recipe you've been using to reproduce this?
>>>
>>> the JIT debug log shows the driver names that it wants to call.  Are you sure
>>> that this driver isn't available anywhere?  I configure the gcc build with
>>> --program-suffix=-8 --program-prefix=x86_64-linux-gnu-, and that one was only
>>> available in one place, /usr/bin.
>>>
>>> Matthias
>>
>> David, the bug report now has two more comments from people that the current
>> behavior is broken.  Please could you review the patch?
> 
> I think libgccjit should use the same strathegy for finding the install location
> like the driver does itself.  I couldn't readily decipher its magic but at least
> there's STANDARD_EXEC_PREFIX which seems to be used as possible
> fallback.

No, it's crtbeginS.o, and libgcc.* which are are not found in the
STANDARD_EXEC_PREFIX.

> In particular your patch doesn't seem to work with a DESTDIR=<path>
> install?

it does. usually you build as configure && make && make install with a DESTDIR
set for only the last step, which doesn't rebuild any object file.

> Can we instead add a --with-gccjit-install-dir= or sth like that (whatever
> path to whatever files the JIT exactly looks for)?

that should be possible, moving the definition of FALLBACK_GCC_EXEC_PREFIX from
the Makefile to a value specified by a configure value.  Or is there already a
macro, that doesn't get prefixed by DESTDIR?

Matthias