这个 C 程序对应的自动机 YA 文件是什么？

Question

In the context of verifying this program using Aorai plugin for frama-c, what would be the corresponding automaton in.ya file format?

void f() {
    ;
}

void g(){
    ;
}

int main(){
    f();
    g();
    return 0;
}

My guess is this

%init: S0;
%accept: S4;

S0 : { CALL(main) } -> S1
   ;
S1 : { CALL(f) } -> S2
   ;
S2 : { CALL(g) } -> S3
   ;
S3 : {RETURN(main) } -> S4
   ;
S4 : -> S4
   ;

But I get this error using Aorai plugin

[aorai] Warning: Call to main does not follow automaton's specification. This path is assumed to be dead
[aorai] Threestateaut.c:12: Warning: 
  Call to main not conforming to automaton (pre-cond). Assuming it is on a dead path

Answer 1

Don't forget that at each event a transition must be taken from the current state of the automaton. Here, when you are in S2 after the CALL to f , the next event that happens is the RETURN from f to main , but the only transition from S2 is guarded by CALL(g) (the beginning of the automaton describes thus a program where f itself calls g ).

To fix this, you can either take the RETURN into account, as in

...
S2: { RETURN(f) } -> S3;
S3: { CALL(g)   } -> S4;
...

or use YA extensions (as described in section 3.1.3 of the manual , which in particular allow indicating that you have a CALL(f) directly followed by a RETURN(f) with:

...
S2: { f() } -> S3;
...

Actually, with these extensions, the complete execution flow can be specified in a more compact way, since you can nest call sequences:

%init: S0;
%accept: S1;

S0 : { main([f();g()]) } -> S1;

S1: -> S1;