Coccinelle: Add iterators/itnull.cocci

/// Many iterators have the property that the first argument is always bound

/// to a real list element, never NULL.  False positives arise for some

/// iterators that do not have this property, or in cases when the loop

/// cursor is reassigned.  The latter should only happen when the matched

/// code is on the way to a loop exit (break, goto, or return).

///

// Confidence: Moderate

// Copyright: (C) 2010 Nicolas Palix, DIKU.  GPLv2.

// Copyright: (C) 2010 Julia Lawall, DIKU.  GPLv2.

// Copyright: (C) 2010 Gilles Muller, INRIA/LiP6.  GPLv2.

// URL: http://coccinelle.lip6.fr/

// Comments:

// Options: -no_includes -include_headers

virtual patch

@@

iterator I;

expression x,E,E1,E2;

statement S,S1,S2;

@@

I(x,...) { <...

(

- if (x == NULL && ...) S

|

- if (x != NULL || ...)

  S

|

- (x == NULL) ||

  E

|

- (x != NULL) &&

  E

|

- (x == NULL && ...) ? E1 :

  E2

|

- (x != NULL || ...) ?

  E1

- : E2

|

- if (x == NULL && ...) S1 else

  S2

|

- if (x != NULL || ...)

  S1

- else S2

|

+ BAD(

  x == NULL

+ )

|

+ BAD(

  x != NULL

+ )

)

  ...> }

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