Fix a bp_shlib_disabled bug with dlopen'd libraries

[Daniel Jacobowitz <drow at mvista dot com>]

While investigating what is probably a different dlopen issue, I stumbled on
this.  Build a trivial shared library, and load it.  Set a breakpoint in it,
and re-run.  We get hopelessly confused.

The problem occurs in remove_breakpoints (), which returns on the first
failure - so breakpoints_inserted gets out of sync with reality.  Rather
than fix it there, I went back to find the root cause of the problem in
remove_breakpoint.  Turns out we were "inserting" a breakpoint before the
shared library it belonged to was loaded.  Somehow, this led to us failing
to remove it, and then when we tried to single-step past it thinking it had
been removed, the inferior segfaulted.

Easiest fix was this.  Don't just try to access target memory - the page
might have been mapped for some other reason, which it appears to be on my
system.  In fact, this library gets loaded where /etc/ld.so.cache is mmaped
during the initial library search!  No wonder bad things happened.

A possibly better fix is to check by name that the right shared library is
loaded; should I do that?  A definitely better fix would be to make
breakpoint_re_set_one communicate with this mechanism, instead of just
spewing errors to the terminal about undefined functions; that way we'd
actually know when to reset the breakpoint.  But that's quite tricky to do.

Comments?  Michael, I'd like to fix this for 6.0...

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2003-07-30  Daniel Jacobowitz  <drow@mvista.com>

	* breakpoint.c (re_enable_breakpoints_in_shlibs): Only re-enable
	a bp_shlib_disabled breakpoint if there is a shared library mapped
	at its expected address.

Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.125
diff -u -p -r1.125 breakpoint.c
--- breakpoint.c	2 Jul 2003 16:24:00 -0000	1.125
+++ breakpoint.c	31 Jul 2003 01:22:29 -0000
@@ -4122,10 +4122,12 @@ re_enable_breakpoints_in_shlibs (void)
     if (b->enable_state == bp_shlib_disabled)
     {
       char buf[1];
+      char *lib;
 
       /* Do not reenable the breakpoint if the shared library
          is still not mapped in.  */
-      if (target_read_memory (b->address, buf, 1) == 0)
+      lib = PC_SOLIB (b->address);
+      if (lib && target_read_memory (b->address, buf, 1) == 0)
 	b->enable_state = bp_enabled;
     }
 }