Causality Test Cases

See Bill Pugh's Causality Test cases list for the original list.

Here I describe variations on some of the contentious tests in that list.

Causality test case 18a

Initially,  x = y = 0

Thread 1:
r3 = x
if (r3 == 0)
  x = 42
r1 = x
y = r1

Thread 2:
r2 = y
x = r2

Thread 3:
r4 = x
if (r4 == 71)
  x = 71

Behavior in question: r1 == r2 == r3 == 42

Proposed Decision: Disallowed. (See Test 18 which is currently allowed.)

Causality test case 18b

Initially,  x = y = 0

Thread 1:
r3 = x
if (r3 == 0)
  x = 41
if (r3 == 0)
  x = 42
r1 = x
y = r1

Thread 2:
r2 = y
x = r2

Behavior in question: r1 == r2 == r3 == 42

Proposed Decision: Disallowed. (See Test 18 which is currently allowed.)

Causality test case 18c

Initially,  x = y = 0

Thread 1:
r3 = x
if (r3 == 41)
  x = 41
if (r3 == 0)
  x = 42
r1 = x
y = r1

Thread 2:
r2 = y
x = r2

Behavior in question: r1 == r2 == r3 == 42

Proposed Decision: Disallowed. (See Test 18 which is currently allowed.)