Compiled a.osl -> a.oso
Compiled b.osl -> b.oso
lazyerror=1:

b: uv = 0 0.5
b: CCin = 
b: Ci = (0.18, 0, 0) * diffuse ((0, 0, 1), "label", "")

b: uv = 1 0.5
b: CCin = 
b: Ci = (0.18, 0, 0) * diffuse ((0, 0, 1), "label", "")

lazyerror=0:
WARNING: Optimization warning:
  group:  unnamed_group_1
  layer:  alayer
  source: a.osl:12
  issue:  error() call present in optimized shader.
a: uv = 0 0.5
a: CCout = (0, 0.18, 0) * diffuse ((0, 0, 1), "label", "")
a: Ci = (0, 0.18, 0) * diffuse ((0, 0, 1), "label", "")

b: uv = 0 0.5
b: CCin = 
b: Ci = (0.18, 0, 0) * diffuse ((0, 0, 1), "label", "")
a: uv = 1 0.5
ERROR: Shader error [a]: u should never be > 0.5!

a: CCout = (0, 0.18, 0) * diffuse ((0, 0, 1), "label", "")
a: Ci = (0, 0.18, 0) * diffuse ((0, 0, 1), "label", "")

b: uv = 1 0.5
b: CCin = 
b: Ci = (0.18, 0, 0) * diffuse ((0, 0, 1), "label", "")

