Pointer issues in Coccinelle

Question

I want to change my code using a Coccinelle script:

// Before modification

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i;
    int *p;

    *p=i;

    return 0;
}

The expected result is:

// After modification

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i;
    int *p;

    if (p!=NULL)
        *p=i;

    return 0;
}

My Coccinelle script is as follows:

@rule1@
type T;
T* ptr;
expression E;
@@

-*ptr= E;
+ if (ptr!=NULL)
+ptr=E;

My script is wrong because the "star" operator is used by Coccinelle. Could anyone help me to know for what the "star" operator is useful because I am a little bit confused about this operator. How can I modify my script to get the expected result?

The C code you presented is just an example right? Since you are reading uninitialized variables. — this, Aug 07 '15 at 16:50
Your example C program would crash (if you're lucky). You're attempting to write to unallocated memory. — Filipe Gonçalves, Aug 07 '15 at 16:52
@FilipeGonçalves: And the modified version reads an uninitialized variable. — EOF, Aug 07 '15 at 16:53
you mean `p = &i` instead of `*p = i ?` it is referred to as `pointer` a c programming book can help you. — Soner from The Ottoman Empire, Aug 07 '15 at 16:53
@itsnotmyrealname See, and it even solves your star problems. :-) — this, Aug 07 '15 at 16:56
Yes it could be another problem to check ,but the problem is not here the problem consists in pattern matching a line that contains "star operator" — fedi, Aug 07 '15 at 17:11
I tried to escape * by a backslash \* but still not working i got this error Fatal error: exception Lexer_cocci.Lexical ("unrecognised symbol, in token rule:\") — fedi, Aug 10 '15 at 07:48

score 2 · Accepted Answer · answered Oct 10 '15 at 14:05

2

Put a space before the *.

Coccinelle uses * to indicate that a match is wanted, rather than a transformation. The * indicates a line that should be highlighted in the result.

answered Oct 10 '15 at 14:05

user2777045

86
3

score 0 · Answer 2 · answered Aug 07 '15 at 16:51

0

I suppose that the * operator is used by cocinelle for pattern matching, x* would match several occurrences of x in a row.

I would try to escape the * with a backslash \*.

Also, the * is missing from your replacement pattern, I think.

answered Aug 07 '15 at 16:51

Jens Gustedt

76,821
6
102
177

In the Coccinelle script above i escaped * with backslash \* but i got an error :Fatal error: exception Lexer_cocci.Lexical ("unrecognised symbol, in token rule:\") – fedi Aug 10 '15 at 07:46

Pointer issues in Coccinelle

2 Answers2