[Scons-users] Custom builder with conditional actions

[jeremy combs]

Bill,

The special section is caused by attributes on variables/functions in the c
file.

-Jeremy

On Tue, May 19, 2015 at 7:16 PM Bill Deegan <bill at baddogconsulting.com>
wrote:

>
>
> On Tuesday, May 19, 2015, jeremy combs <combs.jeremy at gmail.com> wrote:
>
>> I am trying to create a builder that performs actions similar to how the
>> Linux kernel does symbol versioning.
>> See (
>> https://github.com/torvalds/linux/blob/c0a80c0c27e5e65b180a25e6c4c2f7ef9e386cd3/scripts/Makefile.build#L200
>> )
>>
>> As a first step I am trying to duplicate the linux kernel's steps as
>> close as I can:
>>
>> 1. Build .o file from .c file
>> 2. if .o file contains special section
>>         2.true.1.  Run:  gcc -E [.c file] | [analaysis program] > [.o.ver
>> file]
>>         2.true.1   Run: ld -T [.o.ver file] -o [other.o file]
>>         2.true.1   Run: mv [other.o file] [.o file]
>>    2.false.1  Copy [.o file] [other.o file]
>>
>> I currently have this with a custom builder to take [.o file] to [other.o
>> file] but in this custom builder I can't use SCons built in actions.  I
>> have to build the gcc -E command line and execute it via subprocesses.  I
>> would like to be able to use the builtin actions as much as possible to
>> maintain compatibility.
>>
>> I have looked at Builders with a generator function, emitters and many
>> examples.  Most of these examples run at evaluation time before the .o
>> files are available to determine the needed actions.  It seems that every
>> option that runs at build context (Scanners and Builders) when the .o files
>> are available prevents me from altering the actions or tree at that time.
>>
>> So after all that I guess my question is: What is the recommended way to
>> do something like this where actions are dependent on source file contents?
>>
>>
> What causes the .o file to have a special section?
> The source file? Preprocessor flags? Othe command line flags during
> compilation?
>
> -Bill
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