First thanks for your quick reply,
After rewritting the code as suggested so that it uses "method vinst i"
(looks much cleaner), I face 2 problems here.
1) After I change the original statement s to a new one s' , I want s'.id
to be the same as s.id. Using the "method vinst", I cannot do this.
2) And the return type of "method vinst" is "Cil.instr list
Cil.visitAction" so I cannot call ChangeTo(new_stmt) .
The two errors are shown in the code below. Hopefully you can help me fix
these problems.
What I intend to do eventually is changing statements "sprintf" to
"snprintf". Note that I don't want to change _all_ of these sprintf
statements but only specific ones based on their sid's.
For example I'd like to change a statement looking like
sprintf(fixed_buf,"a string\n"); where fixed_buff is an array holding
char (e.g., char fixed_buff[100])
to
snprintf(fixed_buf,sizeof(fixed_buf),"a string\n");
---------------
class sprintfV ? file = object
inherit nopCilVisitor
method vstmt s = (
match s.skind with
|If (_, _, _, _) |Switch (_, _, _, _) |Block _ -> DoChildren
|Instr il when s.sid == WHAT_I_WANT -> DoChildren
|_ -> SkipChildren
)
method vinst i = (
match i with
|Call (None,Lval(Var v,os),expl,loc) -> (
v.vname <- v.vname ^ "_NEW" ;
let new_stmt = mkStmtOneInstr (Call(None,Lval(Var v,os),expl,loc))
in
(*new_stmt.sid <- s.sid; (* ERROR: I cannot change the sid
because s is no longer known*)
ChangeTo(new_stmt) (*ERROR: it expects Cil.instr list
Cil.visitAction*)
)
|_ -> SkipChildren
)
end
VN -
On Thu, Dec 17, 2009 at 1:58 AM, Gabriel Kerneis <[email protected]>wrote:
> Hi,
>
> Your code might work on simple examples, but it will probably break on
> real programms. Could you give a real example of what you are trying to
> do? Don't you want to change the name of the function in it's
> definition too? What if there are function pointers? All this can be
> changed very easily, but you have to define precisely what you want.
>
> If you wished to rename the function everywhere (definition, use, etc.),
> then the following very simple code would be enough:
>
> class testVisitor = object
> inherit nopCilVisitor
>
> method vvdec vi =
> if List.mem vi.vname ["foo"; "bar"]
> then vi.vname <- vi.vname ^ "_new"
> (* No ChangeTo, imperative mutation *);
> SkipChildren
>
> end
>
> Back to your code.
>
> You should use the various methods of the cil visitor to make things
> easier to read. Moreover, this would have let you spot the fact that you
> do NOT dive into Block, If, and other statements. Therefore, you only
> perform variable substitution in top-level instructions. You cut the
> Instr statement to keep only the first element: what if the function you
> are interested in is later in the call sequence? Check out List.map in
> the OCaml doc, it might help you a lot. Using ChangeTo with statements
> can be tricky, too: this potentially breaks gotos (read the CIL API
> documentation, this is mentionned). One last thing: use richer patterns
> in your match cases (see vinst below).
>
> class testVisitor = object
> inherit nopCilVisitor
>
> method vinst i = match i with
> | Call(None, Lval (Var lv, NoOffset), es,loc) ->
> (* Do what you want here --- I do not understand exactly what you
> want *)
> let lv' = (* ... *) in
> ChangeTo (Call(None, Lval (Var lv', NoOffset), es,loc))
> | Call(None, _, _, _) ->
> debug "don't know";
> SkipChildren
> | _ -> SkipChildren
>
> method vstmt s = match s.skind with
> | Instr [] -> SkipChildren (* this is useless, but I put it there to
> show you a convenient way to remove
> if/else in your code *)
> | Instr l ->
> debug "gh\n";
> if s.sid = WHAT_I_WANT (* I'm not sure how you can figure out
> which sid you want, but anyway... *)
> then DoChildren
> else SkipChildren
> | _ -> DoChildren
>
> end
>
> Regards,
> --
> Gabriel
>
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