x86_64-pc-linux-gnu-g++ -DHAVE_CONFIG_H -DUSE_OPENSSL -DPCAPPLAY -DRTP_STREAM   -DHAVE_EPOLL -I. -I./include   -D__LINUX -I./include -Wall -pedantic  -O2 -march=native -pipe -c -o src/sipp-sipp.o `test -f 'src/sipp.cpp' || echo './'`src/sipp.cpp
In file included from ./include/strings.hpp:24,
                 from ./include/sipp.hpp:484,
                 from src/sipp.cpp:41:
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/cstddef:52:8: error: expected unqualified-id before string constant
   52 | extern "C++"
      |        ^~~~~