[Scons-dev] Clang support
Paweł Tomulik
ptomulik at meil.pw.edu.pl
Mon Jan 5 20:56:52 EST 2015
Thanks Bill,
I took a look at manpage and user docs. It says how we may "specify
tools" and not much more.
As I understand, this allows us to specify what tools are **required**
for our project (sorry, this is not clearly stated by docs so I may be
wrong here). This doesn't seem to provide a way to define
**alternatives** for a tool (under a given platform). Let's take an example:
# SConstruct
# Let's say I prefer clang but allow gcc (or reverse)
env = Environment(tools = [])
env.Tool('gnulink')
env.Tool('gcc')
env.Tool('clang')
env.Program('hello.c')
/* hello.c */
int main() { return 0; }
Now, some real test:
1. Installed gcc, but not clang:
ptomulik at debian:~/test1$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
clang -o hello.o -c hello.c
sh: 1: clang: not found
scons: *** [hello.o] Error 127
scons: building terminated because of errors.
2. Installed clang but not gcc:
ptomulik at debian:~/test1$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
clang -o hello.o -c hello.c
clang -o hello hello.o
scons: done building targets.
3. Installed both gcc and clang
ptomulik at debian:~/test1$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
clang -o hello.o -c hello.c
clang -o hello hello.o
scons: done building targets.
ptomulik at debian:~/test1$ scons -v
SCons by Steven Knight et al.:
script: v2.3.1, 2014/03/02 14:18:15, by garyo on lubuntu
engine: v2.3.1, 2014/03/02 14:18:15, by garyo on lubuntu
engine path: ['/usr/lib/scons/SCons']
Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011, 2012, 2013, 2014 The SCons Foundation
Clearly, this does not work as expected.
The Tool('gcc') always returns None and does not throw exception.
One way, to cimcurvent this is to determine manually what compilers are
available and then provide approptiate argument to env.Tool(), but will
my compiler search work better than the "internal search" performed by
Tool()?
W dniu 06.01.2015 o 01:15, Bill Deegan pisze:
> Pawel,
>
> Take a look at Environment() in the Man Page and look at it's tools
> argument.
> There should also be info in the users guide.
> The default behavior when no tools= is specified is supposed to be
> reasonable, but developers can always do what they want.
> Often I use Environment(tools=[]) and then env.Tool('gcc')... to be
> very explicit
>
> -Bill
>
> On Mon, Jan 5, 2015 at 4:13 PM, Paweł Tomulik <ptomulik at meil.pw.edu.pl
> <mailto:ptomulik at meil.pw.edu.pl>> wrote:
>
> Well, I thought that there were just defaults for given platform,
> for example gcc for Linux (so it used gcc, if it's installed or
> fails if it's not, even if other supported compilers are
> available)?. Am I wrong?
>
> W dniu 06.01.2015 o 01:08, Bill Deegan pisze:
>> Pawel,
>>
>> It's always been possible to set tool preference in the
>> Environment() creation.
>> As far as allowing a user to override such via local settings,
>> that's be up to the project using SCons.
>>
>> Allowing such by default would likely cause more issues than it
>> solves as one of the core functional requirements of SCons is
>> that it enables a reproducible build regardless of the users
>> environment.
>> (This is to enable production software builds, as opposed to open
>> source builds which typically want autoconf like behavior, which
>> is also core functional requirement for SCons to enable)
>>
>> -Bill
>>
>>
>> On Mon, Jan 5, 2015 at 4:02 PM, Michael Jarvis
>> <mjarvis.tx.08 at gmail.com <mailto:mjarvis.tx.08 at gmail.com>> wrote:
>>
>> Clang can (mostly) emulate gcc, while the reverse is not
>> true. I would say default to gcc as well.
>>
>> On Mon, Jan 5, 2015 at 6:00 PM, Bill Deegan
>> <bill at baddogconsulting.com
>> <mailto:bill at baddogconsulting.com>> wrote:
>>
>> I'd say on linux default to gcc.
>> If we add clang tools the user can always override them
>> if they wish to.
>>
>> -Bill
>>
>> On Mon, Jan 5, 2015 at 3:58 PM, William Blevins
>> <wblevins001 at gmail.com <mailto:wblevins001 at gmail.com>> wrote:
>>
>> Im not sure what percentage of linux devs use clang
>> vs gcc, but my personal experience is gcc is more
>> widely used.
>>
>> Yet another gcc user,
>> William
>>
>> On Jan 5, 2015 6:51 PM, "Russel Winder"
>> <russel at winder.org.uk <mailto:russel at winder.org.uk>>
>> wrote:
>>
>> On Mon, 2015-01-05 at 13:48 +0100, Paweł Tomulik
>> wrote:
>> […]
>> > I have a project where I just set construction
>> variables CC=clang and
>> > CXX=clang++ and it works well (I check
>> existence of these compilers with
>> > SConf, so I don't need the Tool machinery to
>> search for the compiler
>> > executables).
>> >
>> > Some time ago I also wrote these two tools:
>> >
>> > https://github.com/ptomulik/scons-tool-clang
>> > https://github.com/ptomulik/scons-tool-clangpp
>> >
>> > but for some (forgotten) reason I don't use them :)
>>
>> This may work fine, but if SCons does not have
>> tools called clang, clang
>> ++, clanglink *AND* detection of clang for the
>> cc, c++ and link tools,
>> then SCons has no credible support for Clang.
>>
>> My real question is whether SCons should prefer
>> clang over gcc for
>> Linux.
>>
>> --
>> Russel.
>> =============================================================================
>> Dr Russel Winder t: +44 20 7585 2200
>> <tel:%2B44%2020%207585%202200> voip:
>> sip:russel.winder at ekiga.net
>> <mailto:sip%3Arussel.winder at ekiga.net>
>> 41 Buckmaster Road m: +44 7770 465 077
>> <tel:%2B44%207770%20465%20077> xmpp:
>> russel at winder.org.uk <mailto:russel at winder.org.uk>
>> London SW11 1EN, UK w: www.russel.org.uk
>> <http://www.russel.org.uk> skype: russel_winder
>>
--
Pawel Tomulik
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