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

Fri May 13 04:44:09 EDT 2016

The stdc++ library tends to be in non-standard locations, since it's
depending on the compiler.
Try
  locate "*libstdc++*so*"
and use the -L option with the correct directory. My g++ uses
/usr/lib/gcc/x86_64-linux-gnu/6/.

Alternative:   use g++ with "-Wl,-fuse-ld=gold" and let g++ deal with it.

On Fri, May 13, 2016 at 10:30 AM, Ale Strooisma
<a.strooisma at student.utwente.nl> wrote:
> Andrew,
>
> inspired by this discussion I decided to try using gold as well. I ran into
> a problem however, and can't seem to find a lot of documentation on gold, so
> I hoped you could shed some light on this problem as you are working with
> gold and scons.
>
> I changed to gold by adding LINK='ld.gold' to my environment object.
> However, now I get a lot of undefined reference errors during the linking
> process - they all seem to come from the standard libraries. I interpret
> this as gold not linking those by default, so I added stdc++ to LIBS, but
> that resulted in "ld.gold: error: cannot find -lstdc++".
>
> Any tips for getting this to work?
>
> Kind regards,
> Ale Strooisma
>
>
> On 13 May 2016 at 00:28, Bill Deegan <bill at baddogconsulting.com> wrote:
>>
>> 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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