Re: [boost] Reminder about links when running b2 headers

Subject: Re: [boost] Reminder about links when running b2 headers
From: Bjørn Roald (bjorn_at_[hidden])
Date: 2013-12-24 17:15:47

On 12/24/2013 10:49 PM, Edward Diener wrote:
> On 12/24/2013 11:46 AM, Steven Watanabe wrote:
>> AMDG
>>
>> On 12/24/2013 08:29 AM, Edward Diener wrote:
>>> There was already a discussion about why the creation of hard links to
>>> individual files in the boost directory is inferior to the creation of
>>> symbolic links when the ability to create symbolic links is supported by
>>> the OS. As a reminder, if a hard link is created and the submodule file
>>> is replaced by git, the hard link will still refer to the old file
>>> contents. Thus testing, when it refers to any of the hard linked header
>>> files in the boost subdirectory, will go awry if this happens.
>>>
>>
>> This actually depends on the timestamp that git sets
>> for the new file.  If it always sets the timestamp
>> on checkout to the current time, then b2 will update
>> the link.
>
> Do you mean that b2 would update the hard links appropriately in the
> boost subdirectory if one reruns './b2 headers' ? That is fine for
> systems that must use hard links, but in that case the user must know
> when to rerun './b2 headers'. That is why symbolic links are the better
> solution when available.

I think we have all reached the conclusion symbolic links are best if 
they work on the system.  But for now there is some caution of making 
changes to this while so many other changes need to be be confirmed to 
work first.

>>> Can we please have this updated at the module boost superproject level
>>> by some Boost Build guru so that symbolic links are created when allowed
>>> by the OS ? Even if, as on Windows, administrator rights are needed to
>>> create symbolic links it seems we could have some b2 headers
>>> alternative, aka 'b2 headers_wadmin', which would create symbolic links
>>> on Windows for users who have administrator rights. Of course on Linux
>>> this is not a problem.
>>>
>>
>> No special target is needed.  If you're
>> running as an administrator, Boost.Build
>> will detect that it can create symlinks.
>
> I assume that you mean that you plan to make it work this way. That
> would be great. When I first ran '.\b2 headers' under Windows 7 I had
> administrator rights but it still created hard links.

He did not say it works that way now.  He said you will not need a 
headers_wadmin target to make it work.

>>> I realize this might not be easy to do even by a Boost Build expert but
>>> unless we want to hear squawks and complaints from Boost
>>> developers/end-users using our git/modular boost setup we need to change
>>> to symbolic links when possible.
>>>
>>
>> It's easy to do.  I just haven't wanted to
>> mess with the git repositories until the
>> dust settles.
>
> I understand this. I just do not want to see this dropped indefinitely,
> since at some point the issue needs to be addressed.

It will be.

-- 
Bjørn