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Message-ID: <33E5280D.6672D029@csl.sri.com>
Date: Sun, 03 Aug 1997 17:53:33 -0700
From: Livio Ricciulli <livio@csl.sri.com>
Organization: SRI International
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Subject: dynamic loading semantic difference
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I have noticed that there is a difference in the behavior 
of dynamically loaded objects between freebsd and (sunos, 
solaris and linux).

When two shareable objects which contain a global variable 
with the same name are loaded,

in freebsd the global variable is shared by the objects
and in (sunos, solaris, linux) the variable is private for each
separate object.

for example, if the two following objects

int global=0;
try0()
{
  int local=0;
  global++;
  local++;
  printf("try0 global=%d local=%d\n",global,local);
} 
---------------------------------------------------
int global=0; 
try1()
{
  int local=0;
  global++;
  local++;
  printf("try1 global=%d local=%d\n",global,local);
}

are loaded with dlopen and dlsym
 
and called as: 
try0();try1();

their output is
FreeBSD
try0 global=0 local=0
try1 global=1 local=0

sunos,solaris,linux
try0 global=0 local=0
try1 global=0 local=0

As I said before, in bsd the global variable is shared while in other
OSs it is not.

Can someone tell me why?
Is there a way to get bsd to conform to the other OSs (because of
inter-operability concerns)?

Thanks in advance, 
Livio Ricciulli.