man page and SO post#1/SO post#2 all suggest that
gettid() was implemented in glibc 2.30. I think I am using GLIBC 2.30-8, according to
ldd --version, but
gcc still complains - warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]. I can ignore the warning, and the program runs fine.
The header I tried to use with
<sys/types.h>, following the man page. Did I miss something?
syscall(SYS_gettid) with header
<sys/syscall.h> triggers no warning from