libmicrohttpd: undefined reference to `pthread_setname_np#GLIBC_2.12' when linking - linker

Question

I am using libmicrohttpd 0.9.53 in my project and decided to update it to the latest version (0.9.71). I am cross-compiling for ARM and this is the output of arm-linux-gcc --version:
arm-linux-gcc (4.4.4_09.06.2010) 4.4.4
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
and the output of /lib/arm-linux-gnueabi/libc.so.6:
GNU C Library (Debian GLIBC 2.19-18+deb8u3) stable release version 2.19, by Roland McGrath et al.
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.8.4.
Compiled on a Linux 3.16.7 system on 2016-02-12.
Available extensions:
crypt add-on version 2.1 by Michael Glad and others
GNU Libidn by Simon Josefsson
Native POSIX Threads Library by Ulrich Drepper et al
BIND-8.2.3-T5B
libc ABIs: UNIQUE
For bug reporting instructions, please see:
<http://www.debian.org/Bugs/>.
The compilation is successful, however, I get these errors when linking with the shared library:
arm-linux-gcc -Llib/libmicrohttpd/lib -Wl,-rpath,./lib -o "proj" build/src/proj.o -lpthread -lm -lmicrohttpd
lib/libmicrohttpd/lib/libmicrohttpd.so: undefined reference to `pthread_setname_np#GLIBC_2.12'
lib/libmicrohttpd/lib/libmicrohttpd.so: undefined reference to `clock_gettime#GLIBC_2.17'
collect2: ld returned 1 exit status
make: *** [makefile:191: proj] Error 1
On the target machine, I ran /lib/arm-linux-gnueabi/libc.so.6 | grep clock_gettime:
782: 000e48e4 116 FUNC GLOBAL DEFAULT 12 __clock_gettime##GLIBC_PRIVATE
1625: 000e48e4 116 FUNC WEAK DEFAULT 12 clock_gettime##GLIBC_2.17
And readelf -Ws /lib/arm-linux-gnueabi/libc.so.6 | grep pthread_setname gives no result.
Apparently, the two symbols mentioned in the error have been added between the old and new releases and it seems like my current version of libc does not define them.
Am I completely off track here? Do I have to somehow update libc? Could you please suggest anything that could point me to the right direction?

Answer 1

It looks like your toolchain defaults -Wl,--as-needed. In this case, link order matters even for shared objects.
Try replacing -lpthread -lm -lmicrohttpd with this:
-lm -lmicrohttpd -lpthread
The clock_gettime#GLIBC_2.17 problem requires a rebuild with the version of glibc in your cross-build environment. It seems it was compiled on the target system (which has glibc 2.19, per your question), but it could have been built against any version that has clock_gettime in libc.so.6, starting with glibc 2.17. Your cross-compilation environment has a glibc version prior to that change (so glibc 2.16 or earlier), so it does not recognize the clock_gettime#GLIBC_2.17 symbol version.