how value flow generate the values of a relational operator

[wy163]

Hi, I made a test file and tried to figure out how the value flow works. I attached the input file and the output from the cppcheck.

#include <stdio.h>

int func();

void main() {
    int k = 0;
    int j = 0;
    k = func();
    if(k > 0 && k < 10) {
        j = k + 1;
        printf("j is %d\n", j);
    }
}

3: int func ( ) ;
4:
5: void main ( ) {
6: int k@var1 ; k@var1 = 0 ;
7: int j@var2 ; j@var2 = 0 ;
8: k@var1 =@exprUNIQUE func (@exprUNIQUE ) ;
9: if ( k@var1 >@exprUNIQUE 0 &&@exprUNIQUE k@var1 <@exprUNIQUE 10 ) {
10: j@var2 =@exprUNIQUE k@var1 +@exprUNIQUE 1 ;
11: printf (@exprUNIQUE "j is %d\n"@exprUNIQUE ,@exprUNIQUE j@var2 ) ;
12: }
13: }

Line 6
  = always 0
  0 always 0
Line 7
  = always 0
  0 always 0
Line 9
  > always {!<=-1,!>=2}
  0 always 0
  && always {!<=-1,!>=2}
  k {>=1,!<=0}
  < {!<=-1,!>=2,>=1}
  10 always 10
Line 10
  = {>=2,!<=1,<=10,!>=11}
  k {>=1,!<=0,<=9,!>=10}
  + {>=2,!<=1,<=10,!>=11}
  1 always 1
Line 11
  "j is %d\n" always "j is %d\n"
  j {symbolic=(k+1),>=2,<=10,!<=1,!>=11}

For line 9,

if(k > 0 && k < 10) {

we get the output '> always {!<=-1,!>=2}'. As I understand, that '!<=-1' is output is because 'k > 0' and we have 'int k = 0' at the beginning, but I an not sure if I am right. But why '!>=2' is output?
Thanks a lot!

[CHR]

The comparison operator is Boolean, so this > always {!<=-1,!>=2} is just the range of possible values.