Multiply defined symbols in dhcp server

[Patrick Baggett]

I was building dhcpd 4.2.0 on IRIX 6.5 using the native system compilers,
and right before linking, I got a huge number of warnings from the linker
talking about multiply defined symbols, specifically:

"unknown_class"
"known_class"
"default_collection"
"collections"

The linker still spat out a binary, but lo and behold, the moment I started
the program, it segfaulted.

Checking dhcpd.h, I found (ln 2900-2904) that these symbols are declared
/without/ the "extern" directive, meaning that each file that includes this
creates a globally-visible copy of this symbol. This is a terrible idea and
almost assuredly illegal. Since the comment above says "class.c", I checked
class.c and found "default_collection" and "collections" being declared and
initialized. I couldn't find "unknown_class" or "known_class" -- it looks
like they aren't used in dhcpd (tried "cat *.c | grep known_class" gave
nothing in server/ dir)

Apparently the linker accepted the first definition of the symbol and
rejected the rest, so that meant that if class.o was not the first file that
linker checked, the dhcp server would segfault since the fields are not
initialized as they are in class.c.



The problem is that when I added these extern definitions, dhclient fails to
link due to an undefined reference to "collections" (remember that
server/class.c had the actual symbol?). Even though I'm not trying to use
dhclient, this is another problem. It seems like the "right" thing to do is
to move the declaration of shared, initialized global data to a separate
file.

I'm also seeing other multiply defined symbols: "remote_port", "local_port",
"dhcp_type_interface" (appearing in "dhclient.o" and "discover.o")

Any thoughts on how to resolve these errors cleanly?


Patrick Baggett
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