[Scons-users] Mark existing file as up-to-date

[Pedro Inácio]

@all, Thank you for your feedback.

@William, the default build action is something like
"foo $IN > $OUT"
I can think of three situations where SCons flags $OUT to be rebuilt,
1. I might change the default build action for something like,
"echo Building $OUT; foo $IN > $OUT"
2. I have recompiled foo, but I know that nothing changes in the output.
3. I may have changed input $IN, but I know that nothing changed in the
output.

In all three situations SCons is right. OUT should be rebuilt.
However, I would like to have control and be able to tell SCons that in all
three situations it does not need to rebuild the file.

@Bill, good idea. I have tried this but it doesn't seem to work as
expected. Perhaps I am doing something wrong. I believe the most pragmatic
approach for me would be to ignore the entire build string.
I replaced
BarBuilder=Builder(action='''
foo $SOURCE > $TARGET
''')
with
BarBuilder=Builder(action='''$(
foo $SOURCE > $TARGET
$)''')
but for some reason SCons keeps flagging files for rebuild whenever I
change the build action, despite the $( $).



On 9 May 2014 00:35, Dirk Bächle <tshortik at gmx.de> wrote:


> Hi Pedro,

>

>

> On 08.05.2014 23:32, Pedro Inácio wrote:

>

>> I am using SCons for data processing.

>> One of the perks is that, unlike traditional compilation projects, each

>> file in my project might have required several hours to compute.

>> Re-building existing files is, in general, not acceptable.

>>

>> [...

>> Any ideas?

>>

>>  I would simply split up your build into two single phases, something

> like "SConstruct.preprocess" where you update all your precious files and

> "SConstruct.postprocess" for all the build steps that use them as sources.

> Then you can manually decide when it's efficient to run the preprocess

> step again.

>

> Hope this helps.

>

> Best regards,

>

> Dirk

>

>

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