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Use when GCD/LCM is computed via an iterative loop that mutates the input parameters and reuses them as both state and divisor, creating loop-carried symbolic dependencies
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Use when printf statements output strings without trailing newlines
Use when array is accessed with direct user input as index (0-based indexing)
Use when the program accesses a precomputed table using an offset (e.g., arr[n-1]) that introduces an arithmetic operation between the symbolic input and the index
Use when loop variables iterate over character values (e.g., ASCII codes) to represent different operations or choices
Use when code uses a loop to search for an input value in an array and then uses the found index for further computation
Use when code reads a fixed number of characters into an array and only accesses individual elements
| name | avoid-iterative-gcd-with-mutated-params |
| description | Use when GCD/LCM is computed via an iterative loop that mutates the input parameters and reuses them as both state and divisor, creating loop-carried symbolic dependencies |
A KLEE-coverage code transformation. Applying it rewrites C source so symbolic execution explores more of the program's behavior.
When GCD/LCM is computed via an iterative loop that mutates the input parameters and reuses them as both state and divisor, creating loop-carried symbolic dependencies
Replace the iterative parameter-mutating gcd loop with a clean recursive gcd(a,b) returning gcd(b, a%b), and express lcm as (a/gcd(a,b))*b using fresh local computation
Recursive gcd produces simpler, smaller per-call symbolic constraints (each call introduces one modulo expression) instead of a loop whose path condition accumulates compounded modulo expressions over mutated variables, letting KLEE's solver discharge queries faster and reach more downstream paths
Before:
#include<stdio.h>
int lcm(int a,int b){
int m;
int p=a*b;
m = a%b;
while(m>0){
a = b;
b = m;
m = a%b;
}
return p/b;
}
int main(){
int n,a,b;
scanf("%d",&n);
scanf("%d %d",&a,&b);
a = lcm(a,b);
while(n>2){
scanf("%d",&b);
a = lcm(a,b);
n--;
}
printf("%d\n",a);
}
After:
#include <stdio.h>
int gcd(int a, int b)
{
if(b==0) return a;
return gcd(b, a%b);
}
int lcm(int a, int b)
{
return (a/gcd(a,b))*b;
}
int a[20];
int main()
{
int n, l, i;
while(scanf("%d", &n)==1){
l = 0;
scanf("%d", &a[0]);
scanf("%d", &a[1]);
l = lcm(a[0], a[1]);
for(i=2; i<n; i++){
scanf("%d", &a[i]);
l = lcm(l, a[i]);
}
printf("%d\n", l);
}
return 0;
}
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