Insufficient memory allocation in C++ generated code

[olomix]

I have found a place where generated C++ code uses array element out of bound.

Steps to reproduce. There is a SMTLevIns template in the circomlib repository: https://github.com/iden3/circomlib/blob/master/circuits/smt/smtlevins.circom

We create a simple circuit circuit1.circom

pragma circom 2.0.0;

include "smt/smtlevins.circom";
include "comparators.circom";

component main = SMTLevIns(40);

And compile it using recent circom version to C++ code:

circom -c -l "<path_to_circomlib>/circuits" circuit1.circom

If we take a look at the SMTLevIns_1_run function inside the generated circuit1_cpp/circuit1.cpp file we can see that there is a variable declaration

FrElement expaux[4];

And later in the code we are trying to use the 5th element of this 4-element long array:

Fr_sub(&expaux[4],&lvar[1],&circuitConstants[1]); // line circom 98