[Dev] Tizen 3.0 proposal for applications launch

Schaufler, Casey casey.schaufler at intel.com
Wed Oct 16 15:06:00 GMT 2013


From: dev-bounces at lists.tizen.org [mailto:dev-bounces at lists.tizen.org] On Behalf Of Carsten Haitzler
Sent: Tuesday, October 15, 2013 8:43 PM
To: dev at lists.tizen.org
Subject: Re: [Dev] Tizen 3.0 proposal for applications launch


On 10/16/2013 01:24 AM, Thiago Macieira wrote:

On terça-feira, 15 de outubro de 2013 17:35:13, Łukasz Stelmach wrote:

This is not madness. Before we had dynamic shared libraries we had

static shared libraries. No runtime linking required, everything is

done via table lookups. You can't delete interfaces from a static

shared library, so they make development slightly more difficult. They

are lots faster.



a.out? I may be too young to remember.



Yeah, that's pre-ELF. It's also before my day. My first Linux install still had

a.out support and libc.so.4, but that was only for compatibility.



ELF is a big beast, however. To speed up, I recommend prelinking libraries,

executables, using techniques like ELF symbol visibility, protected

visibility, -Bsymbolic, etc.

i'm not so sure on prelinking. it does have perf upsides, but comes with downsides. namely ANY change of a shared lib (eg upgrade, security fix etc.) requires re-running prelink on all binaries and other shred libs that depend on it. this is costly and requires a lot of tracking. it also negates the ability to keep md5/sha1 hashes of all files in a "secure place" and compare against it to detect intrusion and hacking... :( prelink is a bit of a faustian bargain... :)

But don't you have those same problems with a launcher? The launcher pre-links everything so the application doesn't get slowed by doing so. If you change a library the launcher needs to do the relinking. Granted, that's one place so it's a little bit better.

And let's be clear. On a deployed phone, how often are you changing system libraries in an API incompatible way? Dynamic libraries are a boon for developers. For product they add unnecessary overhead and precious little else.







See

http://www.macieira.org/blog/2012/01/sorry-state-of-dynamic-libraries-on-linux/

http://www.macieira.org/blog/2012/01/update-and-benchmark-on-the-dynamic-library-proposals/




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