Paul Kranenburg's description:
ld is in error here, assuming that symbols with N_EXT set always have an
entry in the (global) symbol table: this is not the case for C++ generated
constructor/destructor symbols. I can reproduce your failure by fudging
a "multiply defined" constructor symbol by hand. Checking for `g == NULL'
seems to be a ok as a fence for now.
So:
for now, in do_file_warnings() we check if g == NULL, before trying to generate
any warning messages. This prevents a NULL pointer dereference.