[Scons-users] Windows Subsystem for Linux (WSL) with SCons for cross-compiling

[Christian Butcher]

Dear Scons-Users List,

I'm currently using SCons to build a series of packages (on a Windows
machine) using a tool that I've written based on the example here:
ToolsForFools <https://github.com/SCons/scons/wiki/ToolsForFools>

I'm now trying to add compilation of a shared library (C++ code) that one
of these packages depends on. I'd like to build using the Windows Subsystem
for Linux to reduce necessary tools on my build machine (i.e. avoid MSVC +
some tool for Linux compilation).

I have 3 target cases - Windows 32-bit, Windows 64-bit and Linux 32-bit,
all as shared libraries (.dll, .dll, .so). The library depends on an
existing 3rd-party library (thirdPartyLib32.dll, thirdPartyLib64.dll,
libthirdParty32.so, currently all stored in the same directory within the
source repository (git, not SCons)).

If I run directly from PowerShell, I can compile the library using command
lines like the following:

W32
wsl i686-w64-mingw32-g++ -o test.dll Relative/Path\ With/Space/srcFileA.cpp
Relative/Path\ With/Space/srcFileB.cpp  -shared -IRelative/Path\
To/Headers -D_WIN32 -DMYLIB_EXPORTS -fvisibility=hidden -O3 -L
Relative/Path\ To/3rdPartyLib -lthirdPartyLib32

W64
wsl x86_64-w64-mingw32-g++ -o test.dll Relative/Path\
With/Space/srcFileA.cpp Relative/Path\ With/Space/srcFileB.cpp  -shared
-IRelative/Path\ To/Headers -D_WIN32 -DMYLIB_EXPORTS -fvisibility=hidden
-O3 -L Relative/Path\ To/3rdPartyLib -lthirdPartyLib64

Linux32
wsl g++ -o test.so  Relative/Path\ With/Space/srcFileA.cpp Relative/Path\
With/Space/srcFileB.cpp -shared -IRelative/Path\ To/Headers -D_WIN32
 -DLINUX_BUILD_MODE -DMYLIB_EXPORTS -fvisibility=hidden -O3
-L Relative/Path\ To/3rdPartyLib -lthirdPartyLib32 -fPIC -m32
-Wno-attributes

(although the -Wno-attributes is probably a) irrelevant to this discussion,
and b) a sign that I need to work on my macro for the Linux compilation...)

I suspect that doing this with an Action might be fairly simple, but would
perhaps lose the ability to check for source changes unless I also use a
Depends call.

If I use SharedLibrary, I keep getting an error that SConsEnvironment
object has no attribute 'SharedLibrary'. I understand this is due to my
overwriting the 'tools' input to the Environment constructor, but using
tools = ['default', 'myTool'] doesn't help.
Why is this? Which values need to be written (and can these be written
after the initialization of the Environment?). I've tried setting things
like env['SHCXX'] and env['CXX'] but this produces no visible change (at
least to the error - the changes are visible when printing env.__dict__).

What is the correct/best/most SCons-like way to do this? Should I be
setting the 'platform' value when creating the Environment (and would I
need to write a new platform object?)? Should I avoid the SharedLibrary
builder and use Action + Depends or similar?

Best regards,
Christian
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