On 16 October 2014 15:43, Johan Alfredsson wrote: > Sorry, my mistake. It turned out that librt was implicitly linked in > in the 4.9.1 case. However, the only things I use from librt are high > precision timers, so a switch to ensure no performance hit in my own > code would be great. Which suggests you were using --enable-libstdcxx-time=rt and so were not using the same configuration for both compilers. If you had told us the actual configurations for both versions that would have been obvious! As Marc says, use a newer glibc to get high-precision timers without needing librt.