[Scons-users] Dependency missed when the included filename is defined by a preprocessor macro

[Bill Deegan]

I can't speak to the why.
That decision predates me.

I think there is/was some code started to implement such.

On Tue, Mar 14, 2017 at 12:18 PM, Andrew C. Morrow <
andrew.c.morrow at gmail.com> wrote:

>
> I've wondered this at times, and I presume there is a good reason, but for
> my own edification I'd like to understand it. Why doesn't SCons, on
> platforms that support it, simply invoke the pre-processor with -MG -MDD or
> whatever and consume the output? That would be a fully faithful
> preprocessor pass, rather than re-implementing the semantics in python.
>
> Thanks,
> Andrew
>
>
> On Tue, Mar 14, 2017 at 11:24 AM, Bill Deegan <bill at baddogconsulting.com>
> wrote:
>
>> I beleive you asked this question on stackoverflow and I pointed you at a
>> pull request which has much of the preprocessor functionality in it.
>> We've not yet merged it, its a work in progress.
>>
>> Please give that a try.
>> -Bill
>> SCons Project co-manager
>>
>> On Tue, Mar 14, 2017 at 8:04 AM, Jean-Baptiste Lab <
>> jeanbaptiste.lab at gmail.com> wrote:
>>
>>> Hi Julien,
>>>
>>> That would require that SCons implements a fully-fledged preprocessor...
>>> It is not the case now and I don't think this is on the roadmap.
>>>
>>> However, you could maybe wrap the Program builder in a function that
>>> would automatically add the HELLO_H value to the dependencies with
>>> env.Depends(), using a new env variable like PREPOC_HEADERS?
>>>
>>> Hope this helps,
>>>
>>> JB
>>>
>>>
>>> On 2017-03-14 11:16, Julien Pommier wrote:
>>>
>>> Hi,
>>>
>>> I’m using a library that #includes a header file whose name is defined
>>> by a preprocessor macro. Unfortunately, scons does not seem to add this
>>> file to the dependency list of the file that does the #include
>>>
>>> Here is a short example:
>>>
>>> I have a hello.c file that is:
>>>
>>> #include HELLO_H
>>> #include <stdio.h>
>>> int main() {
>>>   printf(MESSAGE);
>>>   return 0;
>>> }
>>>
>>> and a hello.h file that is:
>>>
>>> #define MESSAGE "HELLO\n”
>>>
>>> My SConstruct is:
>>>
>>> env=Environment()
>>> env.Append(CPPDEFINES={'HELLO_H':'\'"hello.h"\'’})
>>> env.Program('hello.c’)
>>>
>>>
>>> The hello program is not rebuilt when I edit the content of ‘hello.h’.
>>>
>>> Is there a workaround for that ? I know I can add a Depends(‘hello.c’,
>>> ‘hello.h’) , but that is not a very convenient solution for me, as I would
>>> have to do it in many places.
>>>
>>> Best regards,
>>> Julien
>>>
>>>
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>>
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>
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