shared.c:

int g_var = 0;

void f1(void)
{
   if (g_var)
     // do something

Then I have an executable that links in the shared library, and
updates the global variable:

main.c:

extern int g_var;

int main(void)
{
   g_var = 1;
   fl();

When I'm inside main(), my de{*filter*} (gdb) tells me that g_var is
indeed equal to 1 before the call to fl().  &g_var contains
0x81823820. When I'm inside fl(), however, gdb tells me that g_var is
0!  When I ask gdb to display &g_var, it gives me 0x450340F0!  Why are
there two different versions of g_var!?!?!?  And how do I fix this?

Use pointers?

It appears to be a bug in gdb!  If I single-step through the code, it
functions correctly.  I'm using gdb 5.1.90CVS-5 on Red Hat 7.3.