...
In this noncompliant code example described in "More Randomness or Less" [Wang 2012], the process ID, time of day, and uninitialized memory junk is used to seed a random number generator. This behavior is characteristic of some distributions derived from Debian that use uninitialized memory as a source of entropy because the value stored in junk is indeterminate. However, because accessing accessing an indeterminate value is undefined behavior, compilers may optimize out the uninitialized variable access completely, leaving only the time and process ID and resulting in a loss of desired entropy.
...