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

Algorithm 2

SSA(ET).

Require: An execution trace ET=⟨𝑠₁,…,𝑠_𝑚⟩.

Ensure: The execution trace in SSA form and a function that maps each variable

    to its maximum index value used in the SSA form.

(1) Let index be a function mapping variables to integers. The initial integer value

  for each variable is 0.

(2) Let ET^′ be the empty sequence.

(3) for  𝑗=1 to 𝑚  do

(4)   If   𝑠_𝑗 is an assignment statement of the form 𝑥=𝐸  then

(5)     Let 𝐸^′ be 𝐸 where all variables 𝑦∈𝐸 are replaced with 𝑦_𝑖𝑛𝑑𝑒𝑥(𝑦).

(6)     Let 𝑖𝑛𝑑𝑒𝑥(𝑥) be 𝑖𝑛𝑑𝑒𝑥(𝑥)+1.

(7)     Add 𝑥_𝑖𝑛𝑑𝑒𝑥(𝑥)=𝐸^′ to the end of the sequence ET^′.

(8)   else

(9)     Let 𝑠^′ be the statement 𝑠_𝑗 where all variables 𝑦∈𝐸 are replaced with

      𝑦_𝑖𝑛𝑑𝑒𝑥(𝑦).

(10)    Add 𝑠^′ to the end of the sequence ET^′.

(11)  end if

(12) end for

(13) Return (ET^′,𝑖𝑛𝑑𝑒𝑥).