[lldb-dev] Windows build questions

Zachary Turner via lldb-dev lldb-dev at lists.llvm.org
Mon Sep 7 13:02:04 PDT 2015

+Stephane because he just went through the pain of getting a working build
on Windows, so he might be able to point out some gotchas.

*About VS 2015*
VS 2015 does not work because of Python.  Technically, it could
theoretically work but you won't be able to run the test suite at all.  I
don't plan to put a significant amount of effort into addressing this.
Instead, this will be solved automatically if / when we address
http://llvm.org/pr24461.  You can use VS 2013 community edition though.
TL;DR of the reason VS 2015 doesn't work is because a) Python and the
program embedding python must be compiled with the same compiler, and b)
Python doesn't compile with VS 2015 because it relies on implementation
details of the CRT, which changed in 2015.

*About Windows 10*
The build shoudl work fine on Windows 10 x64.  That's what I use every
day.  But you should still build an x86 LLDB, not an x64 one.  x64 should
work in theory (insofar as the build should succeed), but the actual
runtime support isn't there yet so many things will fail.

A couple of things you might run into:

1) Make sure PYTHONHOME and PYTHONPATH are *not* set, otherwise LLDB's
python and system python can run into conflicts.

2) Make sure you check out and build LLD, test executables must be linked
with LLD or they will not have debug info.  Also, make sure you specify
LLDB_TEST_COMPILER on the cmake command line to point to a clang.exe (If
you use a release clang then ninja check-lldb will be faster by an order of

3) Make sure you build Python from source, run the
install-custom-python.py, and specify -DPYTHON_HOME on the CMake command

Most of this is covered on the website build instructions, but I admit it's
a lot of steps, and it's easy to miss one.  Solving pr24461 should greatly
simplify everything about building on Windows when I finally get around to
it, but it's a lot of work.  Still follow the build instructions anyway
because there's other things as well, but the above 3 are probably the most
likely to trip you up.

On Mon, Sep 7, 2015 at 10:33 AM Todd Fiala via lldb-dev <
lldb-dev at lists.llvm.org> wrote:

> Hi all,
> I've read the Windows lldb build instructions.  I have a few questions
> just to verify before I put too much time into that end:
> * Has the build been vetted on Windows 10 64-bit yet?
> * Can Visual Studio 2015 Community Edition work as the compiler toolchain?
>  (VS 2012+ is listed as okay, so I'm hoping yes).
> Thanks!
> --
> -Todd
> _______________________________________________
> lldb-dev mailing list
> lldb-dev at lists.llvm.org
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