Hello, uClibc-ng is missing the definition of RUSAGE_THREAD. It is available in glibc: sysdeps/unix/sysv/linux/alpha/bits/resource.h: RUSAGE_THREAD = 1 sysdeps/unix/sysv/linux/bits/resource.h: RUSAGE_THREAD = 1 sysdeps/unix/sysv/linux/mips/bits/resource.h: RUSAGE_THREAD = 1 sysdeps/unix/sysv/linux/sparc/bits/resource.h: RUSAGE_THREAD = 1 We have a real-world usage of RUSAGE_THREAD by the pistache project, https://github.com/oktal/pistache. Best regards, Thomas -- Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com