ATAN2 (man3p)
atan2, atan2f, atan2l — arc tangent functions
atan2, atan2f, atan2l — arc tangent functions
pthread_join — wait for thread termination
setreuid — set real and effective user IDs
wcswidth — number of column positions of a wide-character string
localeconv — return locale-specific information
strerror, strerror_l, strerror_r — get error message string
sendto — send a message on a socket
setvbuf — assign buffering to a stream
chmod, fchmodat — change mode of a file
wcstoimax, wcstoumax — convert a wide-character string to an integer type