opencount set to 2 on dlopen using glibc 2.2.5-16

[Dan Towner]

Hi all,

I am using the dlopen/dlclose functions to dynamically load a set of
library functions. The library is written in C++ (with extern "C"
functions), and the program which uses the dl* functions is written in
C. For one particular library that I load, I was getting strange
errors, which I eventually traced to a sequence something like:

handle = dlopen(someFile)
...
dlclose(handle);
dlopen(someFile);

This closes a library, and reopens it, effectively resetting the
libraries internal structures. I discovered that the dlclose wasn't
actually unloading the library, and thus when the library was
reopened, the original library structures were still present, and
caused various problems.

I eventually traced the reason for the library not being unloaded
(using LD_DEBUG=files), which is that the opencount appears to be set
to 2, the first time the library is loaded:

19792:  calling init: ./addDi.gdb
19792:
19792:  opening file=./addDi.gdb; opencount == 2

Thus, when I call dlclose, the opencount goes to 1, and the library is
not unloaded.

I cannot determine the reason why the opencount is set to 2 the first
time? How do I interpret the LD debug files to work out why this is
set like this?

I do not get this problem when using glibc 2.2.2-6.1 (Mandrake 8).

thanks,

dan.

=============================================================================
Daniel Towner
picoChip Designs Ltd., Riverside Buildings, 108, Walcot Street, BATH, 
BA1 5BG
address@hidden
07786 702589