...
[N1401-C1X Draft] Section 7.21.2.1 rand() function, Section 7.21.4.6 getenv() function, Section 7.22.5.8 strtok() function, Section 7.22.6.2 strerror() function, Section 7.25.3.1 asctime() function, Section 7.25.3.2 ctime() function
[Historical information about POSIX.1 Thread Safety]
...
CON32-C. When data must be accessed by multiple threads, provide a mutex and guarantee no adjacent data is also accessed 14. Concurrency (CON)