[tarantool-patches] Re: [PATCH v1 1/1] lua: fix strange behaviour of tonumber64

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Thanks for the patch! See 4 comments below.

On 13/07/2018 14:21, Kirill Shcherbatov wrote:
> Function tonumber64 has worked incorrectly with values less
> than LLONG_MIN.
> Now it works in the interval [LLONG_MIN, ULLONG_MAX] returning
> nil otherwise.
> 
> Closes #3466.
> ---
> Branch: https://github.com/tarantool/tarantool/compare/kshch/gh-3466-tonumber64-strange-behaviour
> Issue: https://github.com/tarantool/tarantool/issues/3466
> 
>   src/lua/init.c         |  6 +++++-
>   test/box/misc.result   | 19 +++++++++++++++++++
>   test/box/misc.test.lua |  8 ++++++++
>   3 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/src/lua/init.c b/src/lua/init.c
> index 9a96030..4b5285d 100644
> --- a/src/lua/init.c
> +++ b/src/lua/init.c
> @@ -222,7 +222,11 @@ lbox_tonumber64(struct lua_State *L)
>   			if (argl == 0) {
>   				lua_pushnil(L);
>   			} else if (negative) {
> -				luaL_pushint64(L, -1 * (long long )result);
> +				if (result > -((unsigned long long )LLONG_MIN)) {

1. Please, do not enclose one-line bodies into {}.

2. How can you cast LLONG_MIN (that is negative) to the unsigned type?

3. Why not 'result > LLONG_MAX'? As I understand, abs(LLONG_MAX) == abs(LLONG_MIN),
it is not? (http://www.cplusplus.com/reference/climits/)

4. Why the function is named to64, but we use non-explicitly sized types?
I mean, why not to use uint64_t result, compare with INT64_MAX etc. According to
the C standard, LLONG_MAX is not restricted with 64 bits.

> +					lua_pushnil(L);
> +				} else {
> +					luaL_pushint64(L, -result);
> +				}
>   			} else {
>   				luaL_pushuint64(L, result);
>   			}