llvm-cov has a bug that the report may contain data that has invalid format, and the following is an example:

Filename  Regions    Missed Regions     Cover   Functions  Missed Functions  Executed  Instantiations   Missed Insts.  Executed       Lines      Missed Lines     Cover
['base/memory/aligned_memory.cc', '57', '57', '0.00%', '1', '1', '0.00%', '1', '1', '0.00%', '64', '6528823037615171174400.00%']

Where there are 13 items in the header, but only 12 in the data, so they don't match. Additionally, the last number '6528823037615171174400.00%' doesn't make any sense.

I will report this bug to llvm-cov, and for now, work this around in the code coverage script.