[Patch] skipping import libraries for performance reasons - direct auto-import of dll's

[Charles Wilson]

Please separate policy arguments from functional arguments.  Whether 
cygwin/mingw should drop import libs is policy.  Whether libtool should 
use/create import libs is policy.  Whether ld should support auto-import 
when doing "link-directly-to-dll" is functional.

[Note: I haven't tested your patch, but it looks mostly ok]

I think the ability to do auto-import when using ld's virtual, 
on-the-fly import lib feature (e.g. link-directly-to-dll) is valuable, 
and complete support (once achieved) should be accepted.

However...

There does not seem to be any support in your patch for the most recent 
auto-import capabilities -- the runtime-pseudo-reloc stuff added by 
Egor.  So, if your patch is accepted as-is, then we have:

(1) if linking to implib, then "full" auto-import support is available; 
--enable-pseudo-reloc allows auto-import of "complex" data (see ld.info).

(2) if linking directly to the dll without an implib, then "partial" 
auto-import is available; --enable-pseudo-reloc has no effect.  And 
doesn't warn that it fails.  I *think* you'd end up with a runtime 
error, if attempting to import "complex" data.

Bad.

Two solutions:

(1) add support for runtime-pseudo-relocs to your patch, and resubmit. 
You might want to work with Egor on this.

(2) When doing "link-directly-to-dll" AND a symbol has a non-zero addend 
(e.g. "complex" data import), then behave as if 
link_info.pei386_runtime_pseudo_reloc = 0, even if --enable-pseudo-reloc 
has been specified.  (Of course, IF --enable-pseudo-reloc has been 
specified and the current link obj is an import lib, then psuedo-reloc 
should occur).  This complex behavior may actually be more difficult -- 
and more confusing -- than simply implementing solution (1).

Minor nit about patch format: watch out for your tab/indentation.  It 
doesn't match the surrounding text in many cases.

Note: yes, I realize that the runtime-pseudo-reloc stuff requires actual 
runtime support (extra code in crt0.o for mingw, extra code in 
cygwin1.dll for cygwin) which does not yet exist.  But it will, 
eventually -- and that's outside ld's purview.  If "normal" 
import-lib-based linking includes support for --enable-pseudo-relocs, 
then "virtual on-the-fly direct" linking should support it too.  Let 
mingw/crt0.o and cygwin/cygwin1.dll take care of themselves.  Downside: 
it's hard for you, Ralf, test test whether you have properly implemented 
the runtime-pseudo-reloc support for virtual on-the-fly direct linking, 
unless you build your own cygwin kernel with the appropriate 
support...talk to Egor...

--
Chuck


--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Bug reporting:         http://cygwin.com/bugs.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/