This appears to be a false positive.
According to:
https://msdn.microsoft.com/en-us/library/9t02bbsx.aspx
...the warning is generated because "If the shift overflowed the 32-bit value, bits are lost." But that's what is actually intended in bitop (it's a 32-bit bit operations library).
I believe the error gets flagged by MSVC because of this line in lua_bitop.c, line #96:
#define BRET(b) lua_pushnumber(L, (lua_Number)(SBits)(b)); return 1;
...since 'b' resolves to (b << n), and lua_Number is a double, then line #116 ends up being this:
static int bit_lshift(lua_State *L) {
uint32_t b = barg(L, 1);
uint32_t n = barg(L, 2) & 31;
lua_pushnumber(L, (double)(int32_t)(b << n));
return 1;
}
So MSVC doesn't like that lua_pushnumber() line, apparently. But that's the intended behavior, because Lua numbers are doubles.
-hadriel
On Feb 7, 2015, at 4:54 PM, Bill Meier <wmeier@xxxxxxxxxxx> wrote:
> Hadriel:
>
> MSVC2013 Code Analysis is giving the following warning:
>
>
> ...\ws-git\epan\wslua\lua_bitop.c(116) : warning C6297: Arithmetic overflow: 32-bit value is shifted, then cast to 64-bit value. Results might not be an expected value.
>
> After quick look at the code, my reaction:
> Uh Oh... Twisty maze of passages
>
> So I'm going to punt.
>
> Can you take a look (or redirect upstream) or whatever ?
>
> Thanks
>
> Bill
