Just curious - why not ninja on Windows? As long as you run vcvars
beforehand (which you have to use anyway even for an MSBuild build)
the output is going to be identical to that which is produced by
MSBuild, but it will be faster.
On Mon Dec 29 2014 at 2:19:21 PM Ted Woodward
<ted.woodw...@codeaurora.org <mailto:ted.woodw...@codeaurora.org>> wrote:
We use the "normal" LLVM layout mentioned below. We use cmake on
64 bit Linux and Windows to set up our build environment, the
build with make on Linux and msbuild on Windows (although, on my
Windows box I open the solution in VS).
We package a full toolset (clang, llvm tools, lldb) together, so
our lldb builds compile everything from source.
--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of Code Aurora
Forum, a Linux Foundation Collaborative Project
*From:*lldb-dev-boun...@cs.uiuc.edu
<mailto:lldb-dev-boun...@cs.uiuc.edu>
[mailto:lldb-dev-boun...@cs.uiuc.edu
<mailto:lldb-dev-boun...@cs.uiuc.edu>] *On Behalf Of *Mario Zechner
*Sent:* Monday, December 29, 2014 4:06 PM
*To:* Zachary Turner
*Cc:* LLDB Development Mailing List; Chandler Carruth
*Subject:* Re: [lldb-dev] Is anyone using the LLDB CMake
standalone build?
FWIW, we use exactly the setup you outlined, for the reasons you
mention: CMake build to build LLDB and dependencies, XCode for
debugging and code editing. We are mostly concerned with Mac OS
X/iOS but are also building for Linux that way.
From an API user perspective it's very nice to have a
cross-platform build that also integrates well with CI servers.
On Dec 29, 2014 10:13 PM, "Zachary Turner" <ztur...@google.com
<mailto:ztur...@google.com>> wrote:
Someone jump in and correct me if I'm wrong, but I believe
there are many reasons that Apple sticks with a
hand-maintained Xcode project. I will try to summarize some of
the reasons here:
1) People are more comfortable editing a native solution file
than editing CMake. I certainly sympathize with this, as I
also strongly prefer editing a Visual Studio solution over a
CMake file. Before working on LLDB, I had actually never even
written a line of CMake before.
2) The Xcode projects generated by CMake are slow, almost to
the point of being unusable. This is a widespread problem
with IDEs, and indeed the MSVC generator suffers from the same
problem. The issue here is related to the size of the project
/ solutions. Every CMake target (which ultimately translates
to a static library or shared library) ends up as a project in
your solution (MSVC) or target in your project (Xcode). This
is the layer at which dependency analysis is performed and
build parallelization is implemented, so having more projects
causes tremendous slowdown in loading projects/solutions and
generating information for intellisense/code completion.
Visual Studio has gotten much better in this regard with
recent versions, but it's still an issue. And I think Xcode
has *not* gotten much better in this regard. In short, an
Xcode generated solution, while it will technically work, is
almost unusable for performance reasons.
3) The Xcode projects generated by CMake aren't as pretty as
hand-generated Xcode projects. It's actually possible to make
prettier generated projects by adding some stuff to the CMake,
but right now they just don't look as nice.
4) Legacy reasons (aka old habits die hard). The LLDB group
at Apple has historically treated LLVM and clang as libraries,
and in the past the only supported way to build LLDB was
against a known revision of clang and LLVM, and only recently
(well, not recent anymore, but legacy decisions can have long
lasting implications) was it changed so that LLDB is expected
to always build against tip of trunk LLVM / clang. One of the
things that came out of this early separation was that an
Xcode build of LLDB does not even use the canonical on-disk
directory hierarchy that all other LLVM subprojects use. A
normal LLVM directory layout looks like this:
llvm
-- tools
---- lldb
---- clang
---- lld
Since LLDB considers itself "not an LLVM subproject, but
rather a standalone project which uses LLVM", it organizes
itself like this:
lldb
-- llvm
---- tools
------ clang
------ lld
Of course, this is just an implementation detail, as we've
shown that lldb can be built as a normal subproject on all
other platforms using the first layout, but this basically
boils down to "old habits die hard". It's what people are used to.
It's certainly easy to sympathize with numbers 1, 3, and 4 but
ultimately I think (or at least hope) that people would be
willing to sacrifice these for the greater good of having a
unified build system. Number 2 however, is probably a
showstopper though.
I'm not sure just how bad the Xcode solution is in terms of
performance, but it's the primary reason why the the
standalone build exists. The standalone build generates a
much smaller project/solution, with only those projects and
targets that are part of LLDB itself, and not projects from
LLVM, clang, etc. It attempts to use an installed LLVM /
clang instead of building one.
One thing that has worked very well for me on Windows is using
my IDE for editing and debugging, but not for building.
There's quite a lot to like about this approach. For starters,
the performance of building from inside the IDE is irrelevant
now, because you're not building from the IDE anymore. For
Visual Studio this makes a huge difference, but I'm not sure
if it makes a difference for Xcode. Another advantage of this
approach is that honestly, ninja is just faster than
everything else. It really is. And not a little bit, but a
lot. I'm a big fan of my IDE and you will only pry it out of
my cold dead hands, but after I tried ninja once or twice, it
was obvious that it was a huge win over building from the
IDE. All it takes me is typing "ninja" from a command shell.
Even I can manage that. Everything else - debugging, code
completion, editing experience, file browsing - still works.
I just don't hit build from inside the IDE.
It would be worth seeing if an approach like this would work
well with people from Apple. Or alternatively, maybe seeing
if the Xcode IDE team within apple would be willing to
prioritize IDE performance in the case of these larger
projects. Visual Studio seems to have come a long way here,
so it doesn't seem impossible for Xcode to improve here, it
just has some work to do.
On Mon Dec 29 2014 at 12:25:20 PM Vince Harron
<vhar...@google.com <mailto:vhar...@google.com>> wrote:
> The main motivation for having a standalone build is
that it's a necessary (but not necessarily sufficient)
precursor to having a usable xcode solution, which is
itself a necessary (but again perhaps not sufficient)
precondition to moving towards a single build system.
I've always assumed that the reason the apple guys don't
generate their xcode projects from cmake is that there is
some magic in the xcode projects that isn't supported by
cmake-xcode project generator. Is there any truth to that?
What is the intended purpose of the LLDB CMake standalone
build? If it is to build against an installed clang/llvm,
it doesn't seem like it's worth the extra complexity...
Vince
On Sun, Dec 28, 2014 at 9:15 AM, Zachary Turner
<ztur...@google.com <mailto:ztur...@google.com>> wrote:
I'm not using the standalone build on Windows, i just
suffer through opening a mega solution. Reid did some
work recently to make it better, but it still doesn't
totally support anyone's needs.
The main motivation for having a standalone build is
that it's a necessary (but not necessarily sufficient)
precursor to having a usable xcode solution, which is
itself a necessary (but again perhaps not sufficient)
precondition to moving towards a single build system.
I'm not versed enough in the LLVM core shared CMake
infrastructure, but I envision a world where
supporting a standalone build requires almost 0
project specific CMake code. Sadly, achieving that
seems quite difficult
On Sun, Dec 28, 2014 at 7:22 AM Chandler Carruth
<chandl...@gmail.com <mailto:chandl...@gmail.com>> wrote:
I thought that Zach was on Windows, but I would be
surprised as I can't get it to work with an
installed Clang. It errors in the cmake step,
unable to find some cmake module.
Is anyone genuinely trying to support this CMake
configuration? It adds quite a bit of complexity.
If so, could they fix this error or suggest how to
fix it on the Clang side? (I help maintain the
Clang cmake build, so I'm happy to enact any
reasonable changes needed...)
This came up because I have a change to the LLDB
CMake build but am currently unable to test it in
a fully standalone build (IE, w/o a source tree).
-Chandler
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Technical Lead Manager |
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