Error while compiling krb 1.5

[Marcus Watts]

Theodore Tso <tytso at MIT.EDU> had replied to
"Henry B. Hotz" <hotz at jpl.nasa.gov>
> Date: Mon, 10 Jul 2006 19:43:20 -0400
> From: Theodore Tso <tytso at MIT.EDU>
> To: "Henry B. Hotz" <hotz at jpl.nasa.gov>
> Subject: Re: Error while compiling krb 1.5
> 
> On Mon, Jul 10, 2006 at 04:22:35PM -0700, Henry B. Hotz wrote:
> > As someone noted, you can use libdl to access symbols in a statically  
> > linked program.  
> 
> Err, no, you can't.  dlopen() is only supported on dynamically linked
> programs.  (This is true as far as I can tell for both Solaris and
> Linux, although for Solaris 10 Sun has effectively eliminated static
> linking by not providing libc.a anymore.)

I believe you're right for Solaris, and probably most "right thinking"
platforms.

For Linux, (more precisely gnu libc) the truth is *far far* stranger.
If you link statically, but call "dlopen", a horrible glob of code
inside of your static copy of libc will reach out, mmap in your dynamic
library, and will then mmap a dynamic copy of libc.so since your
dynamic library probably claims it needs that, after which it will then
mmap in a dynamic copy of ld-linux.so, since libc.so claims it needs
that.  I find the last part particularly baffling.  Oh, and your minimal
sized "static" program to do all this is half a meg in size.
All this can happen even if you don't actually call dlopen directly; calling
"gethostbyname" is good enough.  So here's a trivial example:

size,k	filename
  2 /afs/umich.edu/user/m/d/mdw/source/gh.c
 11 /afs/umich.edu/user/m/d/mdw/source/gh
528 /afs/umich.edu/user/m/d/mdw/source/gh.static
 24 /afs/umich.edu/user/m/d/mdw/source/gh.diet

gh.diet is compiled with "diet cc".  Same version of gcc, completely
different library (unfortunately, GPL'd).
	
				-Marcus