In the last episode (Dec 29), Charlie Root said:
> I expect (want) a runtime error but I do expect it to compile when
> linked with the openldap libraries. Here's my quandery:
>
> vv# gcc -L/usr/local/lib -I/usr/local/include -lldap -llber test.c
> /tmp/ccj67244.o: In function `main':
> /tmp/ccj67244.o(.text+0x7): undefined reference to `ldap_init'
>
> Very odd... but if I changed the ordering of the arguments:
>
> vv# gcc -L/usr/local/lib -I/usr/local/include test.c -lldap -llber
> vv#
>
> It compiles fine. I thought gcc proccessed files in the order in which
> they appeard? I further thought that the only difference between
> specifying a fullname and using -l was that -l surrounding the name
> with lib*.a and searched multiple directories. If thats all true why
> would the ordering matter here?
-l specifies libraries. Libraries are special in that symbols are only
used when *needed*. Your "-lldap -llber test.c" basically was a no-op
for the libraries, since there were no unresolved symbols until
"test.o" got linked in and asked for "ldap_init". But by that time it
was too late. Moving the libs to the end of the commandline lets them
resolve the "ldap_init" symbol. This is why you always see libraries
at the *end* of commandlines :)
--
Dan Nelson
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