[Cocci] 2 basic question

[Nicholas Mc Guire]

Hi !

Trying to do some verification of the coccinelle tool
it self and one of the tasks was to estimate false
negatives (so reliability not accuracy). To be able
to do that the first task was to determin if a semantic
patch specification would actually be looking at all
instances. The following trivial cocci spec was used:

<snip>
virtual report

@found@
position p;
@@

***@p(...)

@script:python depends on report@
p << found.p;
@@
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)
<snip>

With this I run coccicheck on 4.18-rc8 (linux-stable)

make coccicheck COCCI=kmalloc1.cocci | tee kmalloc.log

which gives me a line count of (wc -l kmalloc.log after
removing the header) 4722 instances

But cscope reports 4746 kmalloc cases - so I´m wondering
if coccinelle is actually checking all cases or where
this difference would come from ?
Is the assumption that the above specification sould actually
report every usage of kmalloc correct ?

The second issue is that to simplify completness verification
I wanted to add simple counters like so:


<snip>
virtual report
@initialize:python@
@@
import sys

count=0

def show():
print("Total %d" % count)

@found@
position p;
@@

***@p(...)

@script:python depends on report@
p << found.p;
@@

count = count + 1
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)

@finalize:python depends on report@
@@
show()
<snip>
this works when run with spach version (spatch --version):
spatch version 1.0.1 with Python support and with PCRE support

And will give me the same as wc -l
Total 4722

but not with a current git version (spatch --version):
spatch version 1.0.7-00500-g97695d0 compiled with OCaml version 4.01.0
Flags passed to the configure script: [none]
OCaml scripting support: yes
Python scripting support: yes
Syntax of regular expresssions: PCRE

where Total 0 is reported

did the python interface change and my usage is obsolete
or is this a regression ?

thx!
hofrat

[Julia Lawall]

Post by Nicholas Mc Guire
Hi !
Trying to do some verification of the coccinelle tool
it self and one of the tasks was to estimate false
negatives (so reliability not accuracy). To be able
to do that the first task was to determin if a semantic
patch specification would actually be looking at all
<snip>
virtual report
@found@
position p;
@@
@script:python depends on report@
p << found.p;
@@
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)
<snip>
With this I run coccicheck on 4.18-rc8 (linux-stable)
make coccicheck COCCI=kmalloc1.cocci | tee kmalloc.log
which gives me a line count of (wc -l kmalloc.log after
removing the header) 4722 instances
But cscope reports 4746 kmalloc cases - so IÂŽm wondering
if coccinelle is actually checking all cases or where
this difference would come from ?
Is the assumption that the above specification sould actually
report every usage of kmalloc correct ?

Coccinelle doesn't process code that it can't parse. The amount of real
function code that is not parsable should be very small, but it is
possible that such code contains a call to kmalloc.

On the other hand, I don't know what cscope gives you. Recently, I have
seen for example a call to kmalloc and then an error message like "kmalloc
failed". So would it find both of them?

Post by Nicholas Mc Guire
The second issue is that to simplify completness verification
<snip>
virtual report
@initialize:python@
@@
import sys
count=0
print("Total %d" % count)
@found@
position p;
@@
@script:python depends on report@
p << found.p;
@@
count = count + 1
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)
@finalize:python depends on report@
@@
show()
<snip>
spatch version 1.0.1 with Python support and with PCRE support
And will give me the same as wc -l
Total 4722
spatch version 1.0.7-00500-g97695d0 compiled with OCaml version 4.01.0
Flags passed to the configure script: [none]
OCaml scripting support: yes
Python scripting support: yes
Syntax of regular expresssions: PCRE
where Total 0 is reported
did the python interface change and my usage is obsolete
or is this a regression ?

I just tested it on drivers/usb and got 347. Did you run it in parallel
in the second case (or with make coccicheck, because by default that runs
in parallel)? If you do that, the counter will only get updated in the
child processes, but the printing happens in the main process. If you
want to run in parallel, you need to merge the values. See
tests/merge_vars_python.cocci. Basically, you write:

@finalize:python@
l1 << merge.v1;
l2 << merge.v2;
l3 << merge.v3;
@@

and then l1 l2 and l3 are lists of the values resulting from the various
iterations. You can then add them up.

julia

[Nicholas Mc Guire]

Post by Julia Lawall

Post by Nicholas Mc Guire
Hi !
Trying to do some verification of the coccinelle tool
it self and one of the tasks was to estimate false
negatives (so reliability not accuracy). To be able
to do that the first task was to determin if a semantic
patch specification would actually be looking at all
<snip>
virtual report
@found@
position p;
@@
@script:python depends on report@
p << found.p;
@@
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)
<snip>
With this I run coccicheck on 4.18-rc8 (linux-stable)
make coccicheck COCCI=kmalloc1.cocci | tee kmalloc.log
which gives me a line count of (wc -l kmalloc.log after
removing the header) 4722 instances
But cscope reports 4746 kmalloc cases - so I´m wondering
if coccinelle is actually checking all cases or where
this difference would come from ?
Is the assumption that the above specification sould actually
report every usage of kmalloc correct ?

Coccinelle doesn't process code that it can't parse. The amount of real
function code that is not parsable should be very small, but it is
possible that such code contains a call to kmalloc.

ok - will try to locate what this could be then

Post by Julia Lawall
On the other hand, I don't know what cscope gives you. Recently, I have
seen for example a call to kmalloc and then an error message like "kmalloc
failed". So would it find both of them?

from my understanding of cscope no - and I just tried a trivial
example - if one searches for regeex then yes if for calls no - but
for trivial examples the counts do not differ :)

Post by Julia Lawall

Post by Nicholas Mc Guire
The second issue is that to simplify completness verification
<snip>
virtual report
@initialize:python@
@@
import sys
count=0
print("Total %d" % count)
@found@
position p;
@@
@script:python depends on report@
p << found.p;
@@
count = count + 1
msg = "kmalloc called"
coccilib.report.print_report(p[0],msg)
@finalize:python depends on report@
@@
show()
<snip>
spatch version 1.0.1 with Python support and with PCRE support
And will give me the same as wc -l
Total 4722
spatch version 1.0.7-00500-g97695d0 compiled with OCaml version 4.01.0
Flags passed to the configure script: [none]
OCaml scripting support: yes
Python scripting support: yes
Syntax of regular expresssions: PCRE
where Total 0 is reported
did the python interface change and my usage is obsolete
or is this a regression ?

I just tested it on drivers/usb and got 347. Did you run it in parallel
in the second case (or with make coccicheck, because by default that runs
in parallel)? If you do that, the counter will only get updated in the
child processes, but the printing happens in the main process. If you
want to run in parallel, you need to merge the values. See
@finalize:python@
l1 << merge.v1;
l2 << merge.v2;
l3 << merge.v3;
@@
and then l1 l2 and l3 are lists of the values resulting from the various
iterations. You can then add them up.

works perfectly - I simply did not notice that on the one sysem
it was running single while on the other concurrent and that
was in fact the reason why it worked.

many thx!
hofrat