[Cocci] How to write a pattern which crosses two functions?

[Cocci] How to write a pattern which crosses two functions?

[Will Lester]

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Hello,
I want to write a script to solve problems of such pattern.
func_a () {
    x = .*alloc();
}
func_b () {
    foo(..., x, ...);
}
That is, a variable x is allocated by func_a and used by func_b in a file.
I wrote a script like this:
fn_a (...) {
...
- X = fn1(...);
...
}
...
fn_b (...) {
...
- fn2 (..., X, ...);
...
}
But an error was reported between two functions, "..." cannot be used there.
Therefore, what is the correct solution to this problem?

Thanks,
Will

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Re: [Cocci] How to write a pattern which crosses two functions?

[Julia Lawall]

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On Tue, 16 Jul 2019, Will Lester wrote:

> Hello,
> I want to write a script to solve problems of such pattern.
> func_a () {
>     x = .*alloc();
> }
> func_b () {
>     foo(..., x, ...);
> }
> That is, a variable x is allocated by func_a and used by func_b in a file.
> I wrote a script like this:
> fn_a (...) {
> ...
> - X = fn1(...);
> ...
> }
> ...
> fn_b (...) {
> ...
> - fn2 (..., X, ...);
> ...
> }
> But an error was reported between two functions, "..." cannot be used there.
> Therefore, what is the correct solution to this problem?

Just make two separate rules.  You can put a name for a rule between the
initial @@ and then you can refer to the name in the second rule to
obtain the value of a metavariable from the first one.  For example:

@r@
identifier x;
@@

x = fn1(...)

@@
identifier r.x;
@@

fn2(...,x,...)

In your example, fn1 should end with alloc.  If you want to declare a
metavariable like that you can use a regular expression:

identifier alloc =~ "alloc$";

I guess this should match names that end with alloc.

julia

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