[Scons-users] Make all Program and SharedLibrary targets implicitly Precious?

Thu May 12 18:28:24 EDT 2016

Andrew,

Looks reasonable.
What happens to the old binary if you os.remove it on one system, when it's
being used on another? (NFS)
Does it crash, or is the file kept alive via inode reference by running
process?

-Bill

On Thu, May 12, 2016 at 4:08 PM, Andrew C. Morrow <andrew.c.morrow at gmail.com
> wrote:

>
> OK, I got something that sort of works for incremental linking. I'm sure
> it can be improved:
>
>
> https://github.com/acmorrow/mongo/blob/0062b8bfa0c24812438f4765fa20755fb5f6fc54/site_scons/site_tools/incremental_link.py
>
> The binaries that ld.gold produces seem terribly broken, but perhaps it
> will be useful on Windows.
>
> I wonder if .Precious should have a mode where it behaves like this by
> default, or if it should take an optional parameter. It seems useful.
>
> On Thu, May 12, 2016 at 12:18 PM, Andrew C. Morrow <
> andrew.c.morrow at gmail.com> wrote:
>
>>
>> Hi Bill -
>>
>> I like this suggestion of adding a PreAction to each executable and
>> shared library, but I don't want to have to explicitly call .AddPreAction
>> on each target.
>>
>> Can you suggest an easy way to achieve the same effect globally for all
>> SharedLibrary and Program targets, without writing a PseudoBuilder? I'm
>> fine though with reaching into the existing builders and altering them.
>>
>> Thanks,
>> Andrew
>>
>> On Sat, Apr 30, 2016 at 4:38 PM, Bill Deegan <bill at baddogconsulting.com>
>> wrote:
>>
>>> Andrew,
>>>
>>> How about a pre-action to mv the existing file to another name, and then
>>> copy it to original name, then incremental link the copy?
>>> That should resolve the crashing bit.
>>>
>>> lsof filename won't help if the files being used on another system, but
>>> would if on current system. (to see if in use)
>>>
>>> -Bill
>>>
>>> On Sat, Apr 30, 2016 at 3:47 PM, Andrew C. Morrow <
>>> andrew.c.morrow at gmail.com> wrote:
>>>
>>>>
>>>> Definitely a possibility. MongoDB probes for compiler support for
>>>> ld.gold and prefers it by default:
>>>>
>>>> https://github.com/mongodb/mongo/blob/master/SConstruct#L2164-L2167
>>>>
>>>> The downside to using incremental linking and making dynamic targets
>>>> Precious is that by overwriting the binaries you end up crashing running
>>>> programs that have them mapped. That happens often enough during developer
>>>> workflow that it is unfortunate.
>>>>
>>>> So, it definitely should be opt-in behavior, and a Tool sounds right
>>>> for that.
>>>>
>>>> I also wonder whether such a Tool might be able to make intelligent use
>>>> of gold's --incremental-base file to avoid the above problem. If you first
>>>> copied the dynamic target aside under a different name, then unlinked the
>>>> original, then used --incremental-base pointing to the moved-aside file,
>>>> perhaps you could avoid crashing programs that have the target mapped. I'm
>>>> not sure though if the cost of the file copy would eat up most of the gains
>>>> from incremental linking.
>>>>
>>>> That sounds complex enough to also warrant a separate Tool.
>>>>
>>>>
>>>> On Fri, Apr 29, 2016 at 1:52 PM, Bill Deegan <bill at baddogconsulting.com
>>>> > wrote:
>>>>
>>>>> Andrew,
>>>>>
>>>>> Might make sense to make a gold linker tool?
>>>>>
>>>>> -Bill
>>>>>
>>>>> On Fri, Apr 29, 2016 at 9:47 AM, Andrew C. Morrow <
>>>>> andrew.c.morrow at gmail.com> wrote:
>>>>>
>>>>>>
>>>>>> Thanks Bill -
>>>>>>
>>>>>> I think that sounds promising, I'll give it a look. If I get it
>>>>>> working well I'll ping the list back and describe my findings.
>>>>>>
>>>>>> Thanks,
>>>>>> Andrew
>>>>>>
>>>>>> On Fri, Apr 29, 2016 at 12:10 PM, Bill Deegan <
>>>>>> bill at baddogconsulting.com> wrote:
>>>>>>
>>>>>>> Andrew,
>>>>>>>
>>>>>>> Likely you want to stick this logic in the emitter for building
>>>>>>> libraries and programs.
>>>>>>> SCons/Tool/link.py  shlib_emitter() is the current logic.
>>>>>>> The environment tracks this in:
>>>>>>> env['SHLIBEMITTER'] which is a list.
>>>>>>> So if you append to SHLIBEMITTER and mark the relevant nodes
>>>>>>> Precious()
>>>>>>> env['PROGEMITTER'] is the emitter for programs. Looks like it's only
>>>>>>> defined for mslink and qt, so you can defined one on non qt/mslink freely
>>>>>>> and do the same.
>>>>>>>
>>>>>>> Hope that helps
>>>>>>> -Bill
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Apr 29, 2016 at 8:52 AM, William Blevins <
>>>>>>> wblevins001 at gmail.com> wrote:
>>>>>>>
>>>>>>>> Andrew,
>>>>>>>>
>>>>>>>> I expect that you could make a Pseudo-Builder that wraps Program
>>>>>>>> and Library calls, and replace the top-level calls with your wrappers.
>>>>>>>>
>>>>>>>> I think you can replace them like env['BUILDERS']['xxxxxx'] =
>>>>>>>> Wrapper or env.AddMethod but I haven't tested this explicitly.
>>>>>>>>
>>>>>>>> https://bitbucket.org/scons/scons/wiki/ToolsForFools
>>>>>>>>
>>>>>>>> V/R,
>>>>>>>> William
>>>>>>>>
>>>>>>>> On Fri, Apr 29, 2016 at 4:21 PM, Andrew C. Morrow <
>>>>>>>> andrew.c.morrow at gmail.com> wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hi -
>>>>>>>>>
>>>>>>>>> Is there a simple way to do this? I'd like to use ld.gold's
>>>>>>>>> incremental linking, but I don't want to need to add .Precious to every
>>>>>>>>> executable and library in my project.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Andrew
>>>>>>>>>
>>>>>>>>>
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