See description at https://lists.mcs.anl.gov/pipermail/darshan-users/2018-November/000516.html

The short version is that recent versions of glibc will translate some open() calls using an inline function in fcntl2.h so that they are __open_2() calls at the glibc library level. __open_2() is not intercepted by Darshan.

Will open PR with wrapper for __open_2(). Is there any other solution?