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Use when the algorithm pads a 2D array with sentinel border values and uses nested initialization loops with per-cell conditionals to set them, creating extra symbolic branches per cell
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基于 SOC 职业分类
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-redundant-bounds-sentinels |
| description | Use when the algorithm pads a 2D array with sentinel border values and uses nested initialization loops with per-cell conditionals to set them, creating extra symbolic branches per cell |
A KLEE-coverage code transformation. Applying it rewrites C source so symbolic execution explores more of the program's behavior.
When the algorithm pads a 2D array with sentinel border values and uses nested initialization loops with per-cell conditionals to set them, creating extra symbolic branches per cell
Replace the padded sentinel array with a tight n×n array and use natural loop bounds (x>=0 && x<n) for boundary detection, initializing all cells uniformly without per-cell branching
KLEE forks on every conditional inside initialization loops; uniform initialization plus arithmetic bound checks collapse many symbolic branches into fewer, simpler path conditions, letting the solver reach the algorithm's interesting logic faster
Before:
#include <stdio.h>
#define N 100
int main(void){
int dx[] = {0,1,0,-1};
int dy[] = {-1,0,1,0};
int map[N+2][N+2];
int datas,d,dd,n;
int x,y;
scanf("%d", &datas);
for (int i=0; i<datas; i++){
// get size
scanf("%d", &n);
// reset map
for (int xx=0; xx<n+2; xx++){
for (int yy=0; yy<n+2; yy++){
if (xx==0 || xx==n+1 || yy==0 || yy==n+1){
map[xx][yy]=-1;
}else {
map[xx][yy]=0;
}
}
}
x=1; y=n; d=0; dd=1;
// set spiral
while(1){
map[x][y]=1;
if (map[x+dx[d]][y+dy[d]]==0){
map[x+dx[dd]][y+dy[dd]]=-1;
} else{
if (map[x+dx[dd]][y+dy[dd]]==-1){
break;
}else{
d = (d+1)%4;
dd = (dd+1)%4;
}
}
x += dx[d];
y += dy[d];
}
// output
for (int yy=1; yy<=n; yy++){
for (int xx=1; xx<=n; xx++){
printf(map[xx][yy]==1?"#":" ");
}
printf("\n");
}
if (i<datas-1) printf("\n");
}
return 0;
}
After:
#include<stdio.h>
int main()
{
const int N = 100;
char a[N][N];
int n,d,caseCount=0,i,j,x,y,dd[]={-1,0,1,0},angle,c;
scanf("%d",&d);
while(d--)
{
scanf("%d",&n);
for(i=0;i<n;++i)for(j=0;j<n;++j)a[i][j]=' ';
x=0;y=n-1;
angle=0;
for(c=0;c<3;++c)
{
for(;x>=0&&y>=0&&x<n&&y<n; x+=dd[(angle+1)%4],y+=dd[angle])
{
a[y][x]='#';
}
x-=dd[(angle+1)%4];
y-=dd[angle];
angle=(angle+1)%4;;
}
if(n>2)
{
for(;n;)
{
c=0;
for(; a[y+2*dd[angle]][x+2*dd[(angle+1)%4]]!='#'; x+=dd[(angle+1)%4],y+=dd[angle])
a[y][x]='#',c++;
if(c<2) break;
angle=(angle+1)%4;;
}
a[y][x]='#';
}
else if(n==2)
a[n-1][n-1]=' ';
printf("%s",(caseCount++?"\n":""));
for(i=0;i<n;++i)
{
for(j=0;j<n;++j)
putchar(a[i][j]);
putchar('\n');
}
}
return 0;
}
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