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

  • From: Vladislav Shpilevoy <v.shpilevoy@xxxxxxxxxxxxx>
  • To: Kirill Shcherbatov <kshcherbatov@xxxxxxxxxxxxx>, tarantool-patches@xxxxxxxxxxxxx
  • Date: Mon, 16 Jul 2018 13:23:36 +0300

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);
                        }

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