[Scons-dev] Clang support

Mon Jan 5 23:03:32 EST 2015

Looks like your clang tool is not properly detecting that the tool is not
there and indicating that..

On Mon, Jan 5, 2015 at 5:56 PM, Paweł Tomulik <ptomulik at meil.pw.edu.pl>
wrote:

>  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>
> 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>
>> 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>
>>> 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>
>>>> 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> 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 <%2B44%2020%207585%202200>
>>>>>>  voip: sip:russel.winder at ekiga.net
>>>>>> 41 Buckmaster Road    m: +44 7770 465 077 <%2B44%207770%20465%20077>
>>>>>>  xmpp: russel at winder.org.uk
>>>>>> London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
>>>>>>
>>>>>
> --
> Pawel Tomulik
>
>
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