I'm trying to compile a statically linked binary with GCC and I'm getting warning messages like:
warning: Using 'getpwnam_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
I don't even know what getwnam_r does, but I assume it's getting called from inside some higher level API. I receive a similar message for gethostbyname.
Why would it not be possible to just statically link these functions in like every other function?
Function calls that need access to NSS or iconv need access will open other libs dynamically, since NSS needs plugins to work (the helper modules like pam_unix.so). When the NSS system dlopens these modules, there will be two conflicting versions of glibc - the one your program brought with it (statically compiled in), and the one dlopen()ed by NSS dependencies. Shit will happen.
This is why you can't build static programs using getpwnam_r and a few other functions.