[Scons-users] Unexpected warning when defining a target twice during reading of SConscripts

[Bill Deegan]

Here's my recipe for finding such in the sources:

$ grep -r "Two different environments" src/engine/SCons/

src/engine/SCons/Builder.py:                    msg = "Two different
environments were specified for target %s,\n\tbut they appear to have the
same action: %s" % (t, action.genstring(tlist, slist, t.env))


Actually it's probably correct.
Each time you call SConscript above, it's creating a new Environment().
SConscripts are evaluated basically by python eval.
There's no shared context between the two evaluations of the same
SConscript in this case.


On Fri, Dec 1, 2017 at 3:37 PM, Andrew Featherstone <
andrew.featherstone at cantab.net> wrote:

> Hi all,
>
> Here's a simple setup using scons 3.0.1
>
> $ ls
> SConscript  SConstruct  foo.in
> $ cat SConstruct
> env_a = Environment()
> env_b = Environment()
> for env in (env_a, env_b):
>     SConscript(
>         'SConscript'
>     )
> $ cat SConscript
> import shutil
>
> env_c = Environment()
>
> def simple_cmd(target, source, env):
>     shutil.copy(str(source[0]), str(target[0]))
>
> env_c.Command('foo.out', 'foo.in', simple_cmd)
>
> The expected behaviour when running scons is that the foo.out is produced
> once. This does happen, but SCons incorrectly (AFAICT) warns that different
> environments are used to build the target foo.out:
>
> $ scons
> scons: Reading SConscript files ...
>
> scons: warning: Two different environments were specified for target
> foo.out,
>         but they appear to have the same action: simple_cmd(target,
> source, env)
> File "C:\Users\Andrew\projects\scons-env\SConscript", line 8, in <module>
> scons: done reading SConscript files.
> scons: Building targets ...
> simple_cmd(["foo.out"], ["foo.in"])
> scons: done building targets.
>
> The output of --taskmastertrace:
>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster:     Considering node <no_state   0   '.'> and its children:
> Taskmaster:        <no_state   0   'foo.in'>
> Taskmaster:        <no_state   0   'foo.out'>
> Taskmaster:        <no_state   0   'SConscript'>
> Taskmaster:        <no_state   0   'SConstruct'>
> Taskmaster:      adjusted ref count: <pending    1   '.'>, child 'foo.in'
> Taskmaster:      adjusted ref count: <pending    2   '.'>, child 'foo.out'
> Taskmaster:      adjusted ref count: <pending    3   '.'>, child
> 'SConscript'
> Taskmaster:      adjusted ref count: <pending    4   '.'>, child
> 'SConstruct'
> Taskmaster:     Considering node <no_state   0   'foo.in'> and its
> children:
> Taskmaster: Evaluating <pending    0   'foo.in'>
>
> Task.make_ready_current(): node <pending    0   'foo.in'>
> Task.prepare():      node <up_to_date 0   'foo.in'>
> Task.executed_with_callbacks(): node <up_to_date 0   'foo.in'>
> Task.postprocess():  node <up_to_date 0   'foo.in'>
> Task.postprocess():  removing <up_to_date 0   'foo.in'>
> Task.postprocess():  adjusted parent ref count <pending    3   '.'>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster:     Considering node <no_state   0   'foo.out'> and its
> children:
> Taskmaster:        <up_to_date 0   'foo.in'>
> Taskmaster: Evaluating <pending    0   'foo.out'>
>
> Task.make_ready_current(): node <pending    0   'foo.out'>
> Task.prepare():      node <executing  0   'foo.out'>
> Task.execute():      node <executing  0   'foo.out'>
> Task.executed_with_callbacks(): node <executing  0   'foo.out'>
> Task.postprocess():  node <executed   0   'foo.out'>
> Task.postprocess():  removing <executed   0   'foo.out'>
> Task.postprocess():  adjusted parent ref count <pending    2   '.'>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster:     Considering node <no_state   0   'SConscript'> and its
> children:
> Taskmaster: Evaluating <pending    0   'SConscript'>
>
> Task.make_ready_current(): node <pending    0   'SConscript'>
> Task.prepare():      node <up_to_date 0   'SConscript'>
> Task.executed_with_callbacks(): node <up_to_date 0   'SConscript'>
> Task.postprocess():  node <up_to_date 0   'SConscript'>
> Task.postprocess():  removing <up_to_date 0   'SConscript'>
> Task.postprocess():  adjusted parent ref count <pending    1   '.'>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster:     Considering node <no_state   0   'SConstruct'> and its
> children:
> Taskmaster: Evaluating <pending    0   'SConstruct'>
>
> Task.make_ready_current(): node <pending    0   'SConstruct'>
> Task.prepare():      node <up_to_date 0   'SConstruct'>
> Task.executed_with_callbacks(): node <up_to_date 0   'SConstruct'>
> Task.postprocess():  node <up_to_date 0   'SConstruct'>
> Task.postprocess():  removing <up_to_date 0   'SConstruct'>
> Task.postprocess():  adjusted parent ref count <pending    0   '.'>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster:     Considering node <pending    0   '.'> and its children:
> Taskmaster:        <up_to_date 0   'foo.in'>
> Taskmaster:        <executed   0   'foo.out'>
> Taskmaster:        <up_to_date 0   'SConscript'>
> Taskmaster:        <up_to_date 0   'SConstruct'>
> Taskmaster: Evaluating <pending    0   '.'>
>
> Task.make_ready_current(): node <pending    0   '.'>
> Task.prepare():      node <executing  0   '.'>
> Task.execute():      node <executing  0   '.'>
> Task.executed_with_callbacks(): node <executing  0   '.'>
> Task.postprocess():  node <executed   0   '.'>
>
> Taskmaster: Looking for a node to evaluate
> Taskmaster: No candidate anymore.
>
> Any ideas on how to debug this further?
>
> Andrew
>
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