[Scons-users] Tech question

[Bill Deegan]

Daniel,

On Thu, Jan 24, 2013 at 3:16 PM, <nileiqi at optusnet.com.au> wrote:


> Thanks Bill,

>

> 1. Scons 1.3.0

>


Any reason you don't move forward to SCons 2.2.0?



> 2. I will take a good reading of manpage, thanks very much.

>


No problemo.
SCons tries to do a good job at documenting the system.
If you find anything which is confusing, please don't hesitate to ask for
clarification.

Hope that helps!

-Bill



> Daniel

>

>

> ----- Original Message -----

> From:

> "SCons users mailing list" <scons-users at scons.org>

>

> To:

> "SCons users mailing list" <scons-users at scons.org>

> Cc:

>

> Sent:

> Thu, 24 Jan 2013 15:07:10 -0800

> Subject:

> Re: [Scons-users] Tech question

>

>

>

> Daniel,

>

> On Thu, Jan 24, 2013 at 2:14 PM, <nileiqi at optusnet.com.au> wrote:

>

>> Hi,

>>

>>

>> I am new to Scons and Python, and currently spend quite amount time to

>> learn other people's code and Scons user guide. Please allow me ask some

>> general  and tech quesitons.

>>

>> Tech question

>> (1) Whta is the main difference between generator and action ? For

>> example, I have two pieces of code

>>

>> ****************** piece 1****************************

>> bld=Builder(action = Action(function_name))

>> env.Append(Builders= { 'foo':bld})

>> *********************************************************

>> ****************** piece 2****************************

>>  bld=Builder(generator = function_name)

>> env.Append(Builders= { 'foo':bld})

>>  **********************************************************

>> when run them, what is the different ?

>>

>

> I'd advise you do a thorough read of the manpage. It delves more into the

> depths than the users guide.

> http://www.scons.org/doc/production/HTML/scons-man.html

>

> From the manpage:

>

> generator

>

> A function that returns a list of actions that will be executed to build

> the target(s) from the source(s). The returned action(s) may be an Action

> object, or anything that can be converted into an Action object (see the

> next section).

>

> The generator function takes four arguments: *source* - a list of source

> nodes, *target* - a list of target nodes, *env* - the construction

> environment,*for_signature* - a Boolean value that specifies whether the

> generator is being called for generating a build signature (as opposed to

> actually executing the command). Example:

>

>

> def g(source, target, env, for_signature):

>     return [["gcc", "-c", "-o"] + target + source]

>

> b = Builder(generator=g)

>

>

>

> The *generator* and *action* arguments must not both be used for the same

> Builder.

>

>

>

> A function that returns a list of actions that will be executed to build

> the target(s) from the source(s). The returned action(s) may be an Action

> object, or anything that can be converted into an Action object (see the

> next section).

>

> The generator function takes four arguments: *source* - a list of source

> nodes, *target* - a list of target nodes, *env* - the construction

> environment,*for_signature* - a Boolean value that specifies whether the

> generator is being called for generating a build signature (as opposed to

> actually executing the command). Example:

>

>

> def g(source, target, env, for_signature):

>     return [["gcc", "-c", "-o"] + target + source]

>

> b = Builder(generator=g)

>

>

>

> The *generator* and *action* arguments must not both be used for the same

> Builder.

>

>

>

>

>> (2) For above piece 1 code, I realize it never execute until at the end

>> of the code, when function Default() is called, why is that ?

>>

>

> SCons builds up information about the dependencies and what to do with

> them from the SConstruct/SConscripts (and any other logic you may be

> pulling in).

> Then it will scan the source tree, figure out the dependencies, and then

> execute the builders logic.

>

> Hope that helps!

> -Bill

>

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