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Use when code uses modulo operations (%) in conditional expressions that involve symbolic variables
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| name | avoid-modulo-in-constraints |
| description | Use when code uses modulo operations (%) in conditional expressions that involve symbolic variables |
A KLEE-coverage code transformation. Applying it rewrites C source so symbolic execution explores more of the program's behavior.
When code uses modulo operations (%) in conditional expressions that involve symbolic variables
Replace integer arithmetic with modulo checks by using floating-point arithmetic and checking if the result is an integer (e.g., checking if rounded value equals original value)
Modulo operations create complex non-linear constraints that are difficult for SMT solvers to reason about, while floating-point comparisons with rounding create simpler constraints that KLEE can explore more efficiently
Before:
#include <stdio.h>
int n;
int main()
{
scanf("%d",&n);
//printf("y");
for (long long i=1;i<=3500;i++)
for (long long j=i;j<=3500;j++)
{
//printf("%lld %lld %lld\n",i,j,(i*j*n) );
if ( (3*i*j>n*(i+j) ) && (i*j*n)%( 4*i*j-n*(i+j) )==0 )
{
printf("%lld %lld %lld\n",i,j,(i*j*n)/(4*i*j-n*(i+j) ) );
return 0;
}
}
}
After:
#include <stdio.h>
#include <math.h>
int main(void){
double n,i,j,k,ans,ap;
scanf("%lf",&n);
ans = 4/n;
for (i=1;i<5000;i++)
{
for (j=1;j<5000;j++)
{
ap = ans - 1/i - 1/j;
if (ap >0)
{
ap = 1.0/ap;
ap = roundl(ap * 10000000) / 10000000;
if ((int)(ap) == ap)
{
printf("%d %d %d",(int)(i),(int)(j),(int)(ap));
return 0;
}
}
}
}
return 0;
}
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