[Cocci] Type propagation of unknown field types in arithmetic operations

[Cocci] Type propagation of unknown field types in arithmetic operations

[Michael Stefaniuc]

[-- Attachment #1: Type: text/plain, Size: 603 bytes --]

Hello,

I've run into a new set of false positives in my quest to remove casts
to self:

If the type of a field is unknown then the cast to int will be kept
  (int)s->unknown

But if that field is involved in an arithmetic operation with a numeric
constant and the result gets casted to int then the cast gets
erroneously removed:
  (int)(s->unknown / 1000)

That happens only for fields as a the cast will be kept in for variables:
  (int)(unknown / 1000)

Also if the type of the field is known and doesn't matches then the cast
is correctly kept.

Test case is attached.


thanks
bye
     michael




[-- Attachment #2: selfcast.cocci --]
[-- Type: text/plain, Size: 51 bytes --]

@ disable drop_cast @
type T;
T E;
@@
- (T)
     E

[-- Attachment #3: type.c --]
[-- Type: text/x-csrc, Size: 431 bytes --]

struct _sk {
    int i;
    long l;
};

int foo(int i, long l, bar b, struct _sk *sk, struct _su *su)
{
    int tmp = (int)i;
    tmp += (int)(i / 1000);
    tmp += (int)l;
    tmp += (int)(l / 1000);
    tmp += (int)b;
    tmp += (int)(b / 1000);
    tmp += (int)sk->i;
    tmp += (int)(sk->i / 1000);
    tmp += (int)sk->l;
    tmp += (int)(sk->l / 1000);
    tmp += (int)su->l;
    tmp += (int)(su->l / 1000);
    return tmp;
}

[-- Attachment #4: type.diff --]
[-- Type: text/x-patch, Size: 610 bytes --]

--- type.c
+++ /tmp/cocci-output-10499-bbfa36-type.c
@@ -5,17 +5,17 @@ struct _sk {
 
 int foo(int i, long l, bar b, struct _sk *sk, struct _su *su)
 {
-    int tmp = (int)i;
-    tmp += (int)(i / 1000);
+    int tmp = i;
+    tmp += (i / 1000);
     tmp += (int)l;
     tmp += (int)(l / 1000);
     tmp += (int)b;
     tmp += (int)(b / 1000);
-    tmp += (int)sk->i;
-    tmp += (int)(sk->i / 1000);
+    tmp += sk->i;
+    tmp += (sk->i / 1000);
     tmp += (int)sk->l;
     tmp += (int)(sk->l / 1000);
     tmp += (int)su->l;
-    tmp += (int)(su->l / 1000);
+    tmp += (su->l / 1000);
     return tmp;
 }

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