I'm having problems with dlopen() -- in certain circumstances, it
core dumps.

I noticed the other day that my perl5 executable, which passed all
tests when I compiled it on NetBSD-1.0, now core dumps when I try
to use the perl function "dbmopen".  Unfortunately, I didn't compile
the executable with debugging information, and "where" from gdb
just gives this:

    (gdb) where
    #0  0x1005e75c in end ()
    #1  0x10069060 in end ()
    #2  0x1005fa6a in end ()
    #3  0x1005f84a in end ()

I figured I probably just need to recompile it, but then I noticed
that one of the programs that perl5's Configure script runs also
core dumps, which the script doesn't deal with correctly.  "fred"
is the name of the program is creates, which tests if names passed
to dlsym() need underscores.  It uses dlopen() to open a shared-library
which only contains one nullary function.  Stepping through fred
with gdb indicates that it crashes in dlopen.

Apparently, fred and perl are crashing for the same reason, because
gdb's "where" gives the same output (except for addrs), and the tail
of their ktraces are also the same.  Here's the tail of the ktrace
for perl when it dumps core trying to load the NDBM dynamically-loaded
module:

  [...]
  7556 perl     CALL  stat
  7556 perl     NAMI  "/usr/local/lib/perl5/netbsd/auto/NDBM_File"
  7556 perl     RET   stat 0
  7556 perl     CALL  stat
  7556 perl     NAMI  "/usr/local/lib/perl5/netbsd/auto/NDBM_File/NDBM_File.so"
  7556 perl     RET   stat 0
  7556 perl     CALL  stat
  7556 perl     NAMI  "/usr/local/lib/perl5/netbsd/auto/NDBM_File/NDBM_File.bs"
  7556 perl     RET   stat 0
  7556 perl     CALL  open
  7556 perl     NAMI  "/usr/local/lib/perl5/netbsd/auto/NDBM_File/NDBM_File.bs"
  7556 perl     RET   open 3
  7556 perl     CALL  fstat
  7556 perl     RET   fstat 0
  7556 perl     CALL  read
  7556 perl     GIO   fd 3 read 248 bytes
       "# NDBM_File DynaLoader bootstrap file for netbsd architecture.
	# Do not edit this file, changes will be lost.
	# This file was automatically generated by the
	# mkbootstrap routine in ExtUtils/MakeMaker.pm.
	@DynaLoader::dl_resolve_using =   qw();
	1;
       "
  7556 perl     RET   read 248/0xf8
  7556 perl     CALL  read
  7556 perl     GIO   fd 3 read 0 bytes
       ""
  7556 perl     RET   read 0
  7556 perl     CALL  close
  7556 perl     RET   close 0
  7556 perl     CALL  open
  7556 perl     NAMI  "/usr/local/lib/perl5/netbsd/auto/NDBM_File/NDBM_File.so"
  7556 perl     RET   open 3
  7556 perl     CALL  read
  7556 perl     GIO   fd 3 read 32 bytes
       "\M-@\M^F\^A\v\0 \0\0\0\^P\0\0\0\0\0\0\M-x\^A\0\0 \0\0\0\0\0\0\0\0\0\0\
	\0"
  7556 perl     RET   read 32/0x20
  7556 perl     CALL  mmap
  7556 perl     RET   mmap 269393920/0x100ea000
  7556 perl     CALL  mprotect
  7556 perl     RET   mprotect 0
  7556 perl     CALL  mmap
  7556 perl     RET   mmap 269406208/0x100ed000
  7556 perl     CALL  close
  7556 perl     RET   close 0
  7556 perl     PSIG  SIGSEGV SIG_DFL
  7556 perl     NAMI  "perl.core"

And yet dynamic loading works for several other modules in perl.

I suspect the bug was introduced in rtld/rtld.c on March 8, the
last time it was modified.  Paul, I'd be happy to provide you with
an account on my machine if it would help, or whatever
binaries/cores/examples you need.

	Mark
--------------------------------------------------------------------
Email: Mark_Weaver@brown.edu           | Brown University
PGP Key: finger mhw@cs.brown.edu       | Dept of Computer Science