Fix #5115 (False positive: redundantAssignment when using a union)

[olabetskyi]

No description provided.

[danmar]

might be a working approach.

[danmar]

will we still warn about some redundant assignments properly? maybe you could add a test case where the read is removed.

I would prioritize that we don't write false positives. but if we don't have false negatives that is nice.

[chrchr-github]

Does this also fix https://trac.cppcheck.net/ticket/10093?

[olabetskyi]

It's suppose to I will add the test for it as well when I finished fixing false negatives

[mptre]

This change seem to have introduced a regression.

$ cat fp.c
void
fp(char *ptr)
{
        union {
                char *s8;
                unsigned long long u64;
        } addr;
        addr.s8 = ptr;
        addr.u64 += 8;
}
$ cppcheck --enable-all fp.c
Checking union.c ...
union.c:9:11: style: Variable 'addr.s8' is reassigned a value before the old one has been used. [redundantAssignment]
 addr.u64 += 8;
          ^
union.c:8:10: note: addr.s8 is assigned
 addr.s8 = ptr;
         ^
union.c:9:11: note: addr.s8 is overwritten
 addr.u64 += 8;
          ^

[olabetskyi]

A small fix will solve it. I will push it

[olabetskyi]

d33d29c fix