counterexample_commandline.dfy(31,20): Error: a postcondition could not be proved on this return path
 Related counterexample:
 WARNING: the following counterexample may be inconsistent or invalid. See dafny.org/dafny/DafnyRef/DafnyRef#sec-counterexamples
 Temporary variables to describe counterexamples: 
 ghost var counterexampleLoopGuard0 : bool := false;
 counterexample_commandline.dfy(21,8): initial state:
 assume this != null && |this.p| > 0 && |s| > 0 && 1 == |s| && '\0' == s[0] && 1 == |this.p| && '?' == this.p[0];
 counterexample_commandline.dfy(22,22):
 assume this != null && |this.p| > 0 && |s| > 0 && 1 == |s| && '\0' == s[0] && false == b && 1 == |this.p| && '?' == this.p[0];
 counterexample_commandline.dfy(23,22):
 assume this != null && |this.p| > 0 && |s| > 0 && 1 == |s| && '\0' == s[0] && false == b && 0 == i && '?' == this.p[0] && 1 == |this.p|;
 counterexample_commandline.dfy(24,12): after some loop iterations:
 counterexampleLoopGuard0 := this != null && |this.p| > 0 && |s| > 0 && 1 == |s| && '\0' == s[0] && false == b && 0 == i && '?' == this.p[0] && 1 == |this.p|;
 
counterexample_commandline.dfy(18,22): Related location: this is the postcondition that could not be proved

Dafny program verifier finished with 1 verified, 1 error
