[flang-dev] CMake standalone and compile flags

[Isuru Fernando via flang-dev]

On Mon, May 4, 2020 at 12:30 PM Mehdi AMINI via flang-dev <
flang-dev at lists.llvm.org> wrote:

>
>
> On Mon, May 4, 2020 at 10:17 AM David Truby <David.Truby at arm.com> wrote:
>
>> Hi Mehdi,
>>
>> That branch enables out of tree builds; I believe there are people that
>> still rely on those which is why we added that branch in when rewriting the
>> CMake infrastructure.
>>
>
> I assume that folks were relying on this before the merge in the monorepo,
> but are there still reason to maintain this from now on? Can we put an
> end-date on it?
> I'm trying to figure out if this is just a transition thing or if this is
> really something useful on the long run (and why).
>

Most LLVM subprojects have out-of-tree builds. For eg: clang, lld, lldb,
libcxx, openmp, clang-rt  and it's a useful option to have. mlir is an
exception.

Isuru


>
>
>> There's an open review to fix a similar issue as is reported in the
>> discussion you linked but it seems to have stalled on a discussion about
>> whether to continue to force Werror on, perhaps you could take a look at
>> that and comment there if it fixes this issue or not?
>>
>> The review is at https://reviews.llvm.org/D78306
>>
>
> Thanks, that was roughly what I was about to start doing!
> In general I think we should avoid doing directly `set(CMAKE_CXX_FLAGS
> ...` and instead use the `add_flag_if_supported` macros provided by LLVM,
> e.g.:
> https://github.com/llvm/llvm-project/blob/master/mlir/lib/CMakeLists.txt#L2
>
> Werror is always difficult to maintain because different compilers (and
> compiler versions) have different handling (possibly even opposite!)
> warnings. It is a good thing to have for developers, but it may be a bit
> hostile to users to have it on by default.
>
> --
> Mehdi
>
>
>
>>
>>
>> Thanks
>> David Truby
>> ------------------------------
>> *From:* flang-dev <flang-dev-bounces at lists.llvm.org> on behalf of Mehdi
>> AMINI via flang-dev <flang-dev at lists.llvm.org>
>> *Sent:* 04 May 2020 18:12
>> *To:* Flang Development List <flang-dev at lists.llvm.org>
>> *Subject:* [flang-dev] CMake standalone and compile flags
>>
>> Hi,
>>
>> I was looking into fixing this error that someone has when building
>> flang: https://llvm.discourse.group/t/error-when-building-with-cmake/935
>>
>> Then I noticed that flang/CMakeLists.txt still has this branch:
>> https://github.com/llvm/llvm-project/blob/master/flang/CMakeLists.txt#L42
>> ; is there anyone that relies on it or can we simplify this file and the
>> way the options are setup?
>>
>> Thanks,
>>
>> --
>> Mehdi
>>
>> _______________________________________________
> flang-dev mailing list
> flang-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/flang-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/flang-dev/attachments/20200504/1ac2ade7/attachment.html>