Is there a particular reason --with-compat isn't enabled by default?

[Maxim Dounin]

Hello!

On Wed, May 16, 2018 at 12:45:11PM -0400, Thomas Ward wrote:

> Maxim,
> 
> 
> On 05/16/2018 12:24 PM, Maxim Dounin wrote:
> > Hello!
> >
> > On Wed, May 16, 2018 at 12:03:51PM -0400, Thomas Ward wrote:
> >
> >> On 05/10/2018 08:47 AM, Maxim Dounin wrote:
> >>> More importantly, "--with-compat" provides compatibility between 
> >>> builds with different configure options.  
> >>>
> >>> Without the "--with-compat" argument, one have to use exactly the 
> >>> same  "./configure" line to build both nginx and a module.  The 
> >>> "--with-compat" option relaxes this restriction, and it is more or 
> >>> less enough to build both nginx and a module with "--with-compat".
> >>>
> >>> This generally simplifies building dynamic modules, and also 
> >>> allows one to load the same module into different nginx variants 
> >>> built with different flags.
> >> Is there a reason, then, that `--with-compat` is not a default build
> >> option?  Is there a particular specific reason it was *not* set as a
> >> default compile-time option?
> > The main reasons are that "--with-compat" is not needed when not 
> > using dynamic modules built separately, and compiling nginx with 
> > "--with-compat" results in slightly less optimal binaries (with 
> > various otherwise unneeded placeholder fields added to 
> > structures).
> >
> > We've considered making it the default when it was introduced, but 
> > decided to keep it as an explicit option then.  This might worth 
> > reconsidering.
> >
> I agree it might be worth a reconsideration, in fact I am a supporter of
> making `--with-compat` a default option, not only to make my job as a
> downstream packager easy, but because this would also benefit the
> nginx.org open-source nginx repository as well.  With the number of
> third-party dynamic modules increasing, and more users wanting to
> utilize them, it may be detrimental to leave it disabled.  When the
> support was first released, and dynamic modules were 'new', it made
> sense to leave it disabled, but with more and more modules becoming
> dynamically-supported it could be detrimental to leave this 'default
> disabled'.
> 
> With specific regard to the nginx.org repositories, at last I checked a
> couple weeks ago, they aren't currently built with `--with-compat`
> (unless I missed a recent change to the OSS packaging on hg.nginx.org),
> which means it's equally difficult for users to use the nginx
> repositories without compiling NGINX themselves with third-party
> modules.  If with-compat becomes the default, then this makes things
> easier for users using the nginx.org repos as well as other downstream
> distributions' packages going forward.

Repositories as available from nginx.org are built with 
"--with-compat" since it was introduced in 2016:

http://hg.nginx.org/pkg-oss/file/tip/rpm/SPECS/Makefile#l256
http://hg.nginx.org/pkg-oss/rev/fa656182ba2a#l3.220

-- 
Maxim Dounin
http://mdounin.ru/