[Scons-users] Problems with SConscript files using variant_dir and duplicate=False

[Daniel Moody]

Ah my mistake, I ran scons first with duplication on, then modified the
SConstruct to disable it and ran scons -c, which scons then did not cleaned
the duplicated files because of my change, so they were still there when I
built again. So that is not working for me either.

On Thu, May 21, 2020 at 4:51 PM Hans-Christian Wild <hchr.wild at gmail.com>
wrote:

> Hi Daniel,
>
> thank you for taking the time to answer! Unfortunately, there are still
> problems.
>
> Firstly, your suggestion does not work for me?! I am puzzled,,
>
> When I just change the following line, the output still reads:
>
> mylib_a, mylib_h = SConscript('../../SConscript', exports='env',
> variant_dir='../../target/mylib', duplicate=False)
>
> /w/Projects/mylib/example/mingw
> $ scons
> scons: Reading SConscript files ...
> scons: done reading SConscript files.
> scons: Building targets ...
> scons: building associated VariantDir targets: .
> gcc -o target\src\main.obj -c -IW:\Projects\mylib\target\mylib\include
> target\src\main.c
> target\src\main.c:4:10: fatal error: Types.h: No such file or directory
>  #include <Types.h>
>           ^~~~~~~~~
> compilation terminated.
> scons: *** [target\src\main.obj] Error 1
> scons: building terminated because of errors.
>
> So only the effect was that SCons has decided to put a absolute path to
> the wrong location, instead of the relative one.
>
> Secondly, I am aware of that sentence from the docs and this is what I
> would like! I need X examples building X different version of mylib.
>
> Also, I assumed that when I do a (in /SConscript)
>
> headers = env.Dir('include/')
>
> by the docs:
>
> Dir(name, [directory]) , env.Dir(name, [directory])
> [...] If no directory is specified, the current script's directory is
> used as the parent.
>
> .. that this would mean that scons remembers a relative path and the
> current SConscript file as parent and is able to compute and abs or
> relative path to if from where ever scons is called our what variant dirs
> you specify.
>
> SCons does so correctly when you have duplication on, if not, it doesn't.
>
> -hans
>
> On Thu, May 21, 2020 at 10:22 PM Daniel Moody <dmoody256 at gmail.com> wrote:
>
>> Also should note, I am not saying its "not a bug", just what worked when
>> I was messing with your example. It seems like its "not a bug" and if you
>> really want your variant dir in the location of the SConstruct you should
>> use duplicated tree. So probably more of a feature request if you were to
>> submit an issue.
>>
>> On Thu, May 21, 2020 at 2:12 PM Daniel Moody <dmoody256 at gmail.com> wrote:
>>
>>> the docs say:
>>> https://scons.org/doc/3.1.2/HTML/scons-man.html#f-SConscript
>>> "The variant_dir argument is interpreted relative to the directory of
>>> the calling SConscript file."
>>>
>>> So in the case the SConstruct is the "calling SConscript" and you are
>>> saying the variant dir for the SConscript should be target/mylib, but its
>>> not, its ../../target/mylib relative to the calling SConstruct.
>>>
>>> So you need to call it like this:
>>> mylib_a, mylib_h = SConscript('../../SConscript', exports='env',
>>> variant_dir='../../target/mylib', duplicate=False)
>>>
>>> For a non duplicated variant dir, the variant dir will be
>>> substituted with the source dir when resolving paths for the build, which
>>> means substituting "target/mylib/include" to "./include" where
>>> 'target/mylib' is the variant dir and '.' is the source dir, will not work
>>> from the calling SConstructs location. It should be substituted with
>>> "../../target/mylib" so the variant dir resolved to the correct location.
>>>
>>> On Thu, May 21, 2020 at 12:54 PM Hans-Christian Wild <
>>> hchr.wild at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> I have two questions about SCons, I have uploaded a *working* example
>>>> as base where SCons does everything nearly as I want it. The problems start
>>>> to occur only when we do slight modifications to this example.
>>>>
>>>> https://github.com/hchrwild/scons01/tree/master
>>>>
>>>> In the project we have a main SConstruct file in `/example/mingw/`
>>>> which imports a library SConscript file from `/`. The SConscript file
>>>> creates its little library for the given environment and returns it
>>>> together with its public header include path. The SConstruct file in turn
>>>> builds an executable linking the static library and using the public header
>>>> include path.
>>>>
>>>> Output:
>>>>
>>>> scons: Reading SConscript files ...
>>>> scons: done reading SConscript files.
>>>> scons: Building targets ...
>>>> scons: building associated VariantDir targets:
>>>> target\mylib\example\mingw
>>>> gcc -o target\src\main.obj -c -Itarget\mylib\include target\src\main.c
>>>> gcc -o target\mylib\src\Assert.obj -c -Itarget\mylib\include
>>>> -Itarget\mylib\src\include target\mylib\src\Assert.c
>>>> ar rc target\mylib\libmylib.a target\mylib\src\Assert.obj
>>>> gcc -o target\mingw-example.exe target\src\main.obj
>>>> target\mylib\libmylib.a
>>>> scons: done building targets.
>>>>
>>>> *Perfect!*
>>>> (Although I don't understand why it prints `building associated
>>>> VariantDir targets: *target\mylib\example\mingw*` which to me does not
>>>> make sense, IMO it should be *`example/mingw/target/mylib`* if
>>>> anything, but let's put that aside..)
>>>>
>>>> *Now the actual problems:*
>>>>
>>>> 1) I don't like that SCons duplicates everything. What I really want is
>>>> an out-of-source variant build. When I set `duplicate=False`, the build
>>>> fails, however:
>>>>
>>>> mylib_a, mylib_h = SConscript('../../SConscript', exports='env',
>>>> variant_dir='target/mylib', duplicate=False)
>>>>
>>>> scons: Reading SConscript files ...
>>>> scons: done reading SConscript files.
>>>> scons: Building targets ...
>>>> scons: building associated VariantDir targets: .
>>>> gcc -o target\src\main.obj -c *-Itarget\mylib\include*
>>>> target\src\main.c
>>>> target\src\main.c:4:10: fatal error: Types.h: No such file or directory
>>>>  #include <Types.h>
>>>>           ^~~~~~~~~
>>>> compilation terminated.
>>>> scons: *** [target\src\main.obj] Error 1
>>>> scons: building terminated because of errors.
>>>>
>>>> As marked in above output, the include path is not updated. The
>>>> SConscript file is at `../../` relative to SConstruct, and the include
>>>> folder is ./include relative to SConscript. Therefore, without duplication,
>>>> the correct include path relative to SConstruct would be `../../include` ,
>>>> which SCons does not seem to compute however. Is this expected or a missing
>>>> feature/bug? I really like the idea, that the SConstruct file really only
>>>> needs to know where the SConscript file is located and having everything
>>>> else being figured out by the build system...
>>>>
>>>> 2) Let's put that aside and keep above change, but hardcode the
>>>> expected include path in SConstruct file:
>>>>
>>>> program = env.Program('target/mingw-example', sources, CPPPATH=[
>>>> '../../include'], LIBS=[mylib_a])
>>>>
>>>> scons: Reading SConscript files ...
>>>> scons: done reading SConscript files.
>>>> scons: Building targets ...
>>>> scons: building associated VariantDir targets: .
>>>> gcc -o target\src\main.obj -c -IW:\Projects\mylib\include
>>>> target\src\main.c
>>>> gcc -o target\mylib\src\Assert.obj -c *-Itarget\mylib\include
>>>> -IW:\Projects\mylib\include -Itarget\mylib\src\include
>>>> -IW:\Projects\mylib\src\include* W:\Projects\mylib\src\Assert.c
>>>> ar rc target\mylib\libmylib.a target\mylib\src\Assert.obj
>>>> gcc -o target\mingw-example.exe target\src\main.obj
>>>> target\mylib\libmylib.a
>>>> scons: done building targets.
>>>>
>>>> Now the compilation succeeds. However, scons has now duplicated the
>>>> include paths for the static library! One time with the invalid
>>>> variant-with-duplication path, and one time with the correct (absolute
>>>> path). Why does it do that? Is this a bug?
>>>>
>>>> Sorry for the long post. Any feedback appreciated!
>>>>
>>>> -hans
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