From: Nobuyoshi Nakada <nobu@...>
Date: 2013-10-11T01:56:02+09:00
Subject: [ruby-core:57817] Re: ruby-2.0.0-p247siphash.c:443: bug report

(13/10/10 23:43), David Binderman wrote:
> I just ran the static analysis tool cppcheck over the source code
> of ruby-2.0.0-p247
> 
> It said
> 
> [siphash.c:443] -> [siphash.c:445]: (warning) Variable 'last' is reassigned a value before the old one has been used. 'break;' missing?
> [siphash.c:445] -> [siphash.c:447]: (warning) Variable 'last' is reassigned a value before the old one has been used. 'break;' missing?
> [siphash.c:447] -> [siphash.c:460]: (warning) Variable 'last' is reassigned a value before the old one has been used. 'break;' missing?
> [siphash.c:460] -> [siphash.c:462]: (warning) Variable 'last' is reassigned a value before the old one has been used. 'break;' missing?
> [siphash.c:462] -> [siphash.c:464]: (warning) Variable 'last' is reassigned a value before the old one has been used. 'break;' missing?
> 
> Source code is
> 
>     switch (len % sizeof(uint64_t)) {
>     case 7:
>         OR_BYTE(6);
>     case 6:
>         OR_BYTE(5);
>     case 5:
>         OR_BYTE(4);

OR_BYTE() macro is defined as:
  #define OR_BYTE(n) (last |= ((uint64_t) end[n]) << ((n) * 8))

So 'last' is actually used before reassignment.

Seems a flaw in cppcheck's analysis.

-- 
Nobu Nakada