foo.cc: In function 'void new_thread()':
foo.cc:7:17: warning: unused variable 'th' [-Wunused-variable]
    7 |         thread *th = new thread(new_thread);
      |                 ^~
/usr/bin/ld: /tmp/ccS8ExGJ.o: in function `new_thread()':
foo.cc:(.text+0x54): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status

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