On Thu, 30 Aug 2012, Dmitry Antipov wrote:
Hello,
Is it possible to use coccinelle to find the structure/union
members which aren't accessed explicitly, via '.' or '->'?
For example, if I have:
struct foo
{
int x;
int y;
int z;
};
and neither X->z nor Y.z (where X is of type 'struct foo *'
and Y is of type 'struct foo') is used, I would like to
get a message about 'z' from type 'struct foo' is never used.
If this isn't possible just now, consider this as the feature
request for the future versions :-).
An implementation is below. It is a rather standard pattern: use position
variables to mark the things that have a property, and then report errors
for everything that is not marked.
The rule ty selects each field in the structure, one by one.
The rules r and rr then take care of the . case and the rules s and ss
take care of the -> case. The rule r finds some object x from which the
field is referenced. The rule rr then puts a position variable on that
field, in the case that some such reference was found (depends on r). The
rules s and ss are similar. Now the bad fields are the ones that are not
marked by either a rr or ss position variable. These are found in the
last rule.
The limitation is that the structure has to be in the same file as the
references, or in a header file that Coccinelle finds when it is treating
the C file. You could use the argument --all-includes and appropriate -I
arguments to get all directly mentioned #include files to be included.
The argument --recursive-includes includes files that are included by
other files, but it may make things extremely slow, if there are many such
files.
julia
@ty@
identifier i,fld;
type T;
position p;
@@
struct i@p {
...
T fld;
...
};
@r@
identifier ty.i;
struct i x;
identifier ty.fld;
@@
x.fld
@rr depends on r@
identifier ty.i,ty.fld;
type ty.T;
position p1,ty.p;
@@
struct i@p {
...
T fld@p1;
...
};
@s@
identifier ty.i;
struct i *x;
identifier ty.fld;
@@
x->fld
@ss depends on s@
identifier ty.i,ty.fld;
type ty.T;
position p2,ty.p;
@@
struct i@p {
...
T fld@p2;
...
};
@@
identifier ty.i,ty.fld;
type ty.T;
position bad!={rr.p1,ss.p2},ty.p;
@@
struct i@p {
...
*T fld@bad;
...
};
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