Post by Robert LaricePost by Julia LawallPost by Julia LawallPost by Robert LariceDear People,
I'm completely new here.
Attached is a small piece of .c and a .cocci file.
There is a "return 41;" in both files, commented out.
If I uncomment this "return 41;" in both files then
spatch will not match the pieces any more.
Could you please help me to undertand and circumvent this issue ?
I have not noticed this problem before, but I suspect that it is due to
the fact that Coccinelle is matching the control-flow path and not the
abstract syntax tree. In a control-flow graph, nothing follows a return.
julia
Thank You,
I tried to sneak around the problem with a second "rule" which
translates "return 42" to "auxiliary(42)".
My intention was to first change the source in such a way
that the "control-flow" graph does not end at the "return",
and then hope that the second (accordingly modified) rule would
match.
This didn't work, I assume I would have to express the idea of
first applying the first rule
then to rebuild the control-flow graph
then try the second rule.
(and finally undo the changes of the first rule in a third rule)
I can not force "rebuild" without invoking spatch myself a second time.
If you change all the returns to something else and then match your
pattern, and then change them it should work.
---
I'm a bit of a maintainer for the "ngspice" project, which has a vast
amount of very old files, and lots of semi duplicated stuff often crying
for a thourough hair wash,
stumbled over this intresting tool, and am tying it for a certain
rewrite I'm currently busy with.
OK,feel free to ask more questions if you run into further issues.
julia
Hello,
Thank you for your help. I've four or five .cocci files now which
do the job at hand for ngspice quite well. The rewrite of return
to something else with two times invocation of spatch did work.
Then I found another simpler way. So thats done.
Playing around, trying to better understand what it means
to have more than one rule, their interaction etc ..
I came to the attached example.
Here I have basically tried to remove the whole body of a function
It seems to work if I use the '*' notation, but doesnt if I use
'+/-'
Can you give me a hint which helps me to understand this ?
For -+, Coccinelle requires that all control-flow paths from the starting
point of the match match the complete rule. So for example a() ... b()
would match the following:
a();
if (x)
b();
else b();
For *, it only requires the existence of such a path.
If you have a -+ somewhere in the semantic patch, then all rules use the
forall semantics. If you have a * somewhere in the semantic patch, then
all rules use the exists semantics.
In your rule r2, you have ... Label: but this label is not reached on the
execution path that ends in return 1. When you have -+ somewhere in the
semantic patch this rule is not satisfied.
If you want to change the default for a rule, you can add exists for
forall to the rule header, or put when exists or when forall on the ...
julia