On Fri, 25 Feb 2022, Johannes Schindelin wrote:

Hi Julia,

On Tue, 22 Feb 2022, Julia Lawall wrote:

quoted

[I]f there are some cases that are useful to do statically, with only
local information, then using Coccinelle could be useful to get the
problem out of the way once and for all.  Coccinelle doesn't support
much processing of strings directly, but you can always write some
python code to test the contents of a string and to create a new one.

Let me know if you want to try this.  You can also check, eg the demo
demos/pythontococci.cocci to see how to create code in a python script and
then use it in a normal SmPL rule.

If some context has to be taken into account and the context in the same
function, then that can also be done with Coccinelle, eg

A
...
B

matches the case where after an A there is a B on all execution paths
(except perhaps those that end in an error exit) and

A
... when exists
B

matches the case where there is a B sometime after executing A, even if
that does not always occur.

If the context that you are interested in is in a called function or is in
the calling context, then Coccinelle might not be the ideal choice.
Coccinelle works on one function at a time, so to do anything
interprocedural, you have to do some hacks.

Right. The code in question is not actually calling a function, but a
macro, and passes a literal string to the macro that we would want to
check statically.

Coccinelle doesn't care about whether a function is called or whether a
macro is called.  It considers everything to be a function.

I did have my doubts that it would be easy with Coccinelle, but since Ævar
seemed so confident, I tried it, struggled, and decided to follow up with
you.

Something like this:

@r1@
expression e;
@@

N(e)

@script:python s@
e << r1.e;
replacement;
@@

if string_ok e
then cocci.include_match(False)
else coccinelle.replacement = "\"better string\""

@@
expression r1.e;
expression s.replacement;
@@
- N(e)
+ N(replacement)

------------------

You can fill in the definition of string_ok and better string.  I think
the \" will be necessary, because the value of an expression metavariable
at the python level is a string, so there should be a string inside of it
to make it a string expression.

julia