Provides determinism via a LD_PRELOAD hook, replacing the getrandom(2) syscall with a Mersenne twister.
This was made to produce deterministic UUIDs in gtirb/ddisasm. Here, the UUIDs are 128-bits and commonly base64 encoded. For visibility, we tweak the first 6 bits of these random generations so the first base64 character is fixed.
To build the .so file for LD_PRELOAD,
makeTo build and run the test binary,
$ make do-test
cc -c -o test.o test.c
cc test.o -o test
g++ -fPIC -ldl -c -o unrandom.o unrandom.cpp
g++ -fPIC -ldl unrandom.o -shared -o libunrandom.so
LD_PRELOAD=$(pwd)/libunrandom.so ./test
x == y : ok
8621d6cc92f81cce 902ccb701fd13acc
x1 == 0x8621d6cc92f81cce : ok
x2 == 0x902ccb701fd13acc : ok
uuid[0] >> 2 == 0b110011 : ok
uuid[0] >> 2 == 0b110011 : ok
uuid[0] >> 2 == 0b110011 : ok
uuid[0] >> 2 == 0b110011 : ok
uuid[0] >> 2 == 0b110011 : ok
Based on whitequark/unrandom.