Combining Slicing and Constraint Solving for Better Debugging: The CONBAS Approach

Algorithm 3

CONSTRAINTS (ET,(𝐼,𝑂), ssa).

Require: An execution trace ET=⟨𝑠₁,…,𝑠_𝑚⟩ in SSA form, a test case (𝐼,𝑂),

 and a function ssa returning the final index value for each variable.

Ensure: The constraint representation of ET and the test case.

(1) Let CO be the empty set.

(2) for all  (𝑥,𝑣)∈𝐼  do

(3) Add “(𝑥_0==𝑣)” to 𝐶𝑂.

(4) end for

(5) for all  (𝑦,𝑤)∈𝑂   do

(6) Add “(𝑦_𝑠𝑠𝑎(𝑦)==𝑤)” to 𝐶𝑂.

(7) end for

(8) for  𝑗=1 to 𝑚   do

(9)   if  𝑠_𝑗 is an assignment statement of the form 𝑥=𝐸  then

(10)    Add “ (AB(𝑖𝑛𝑑𝑒𝑥(𝑠_𝑗))∨(𝑥==𝐸))” to 𝐶𝑂.

(11)  else

(12)     Let 𝑐 be the condition of 𝑠_𝑗 where & is replaced with ∧ and | with ∨.

(13)     Add “(AB(𝑖𝑛𝑑𝑒𝑥(𝑠_𝑗))∨(𝑐))” to 𝐶𝑂.

(14)  end if

(15) end for

(16) Return 𝐶𝑂.