Re: [Tarantool-patches] [PATCH luajit 2/2] Fix tonumber("-0") in dual-number mode.

[sergos via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi!

Thanks for the patch, jut nits in the changelog.

LGTM

Sergos

> On 26 Jan 2022, at 15:19, Sergey Kaplun <skaplun@tarantool.org> wrote:
> 
> From: Mike Pall <mike>
> 
> Reported by Sergey Kaplun.
> 
> For DUALNUM build `tonumber("-0x0")` or `tonumber("-0")` returns 0
    the            a call to             to
> instead -0 due to the STRSCAN_OPT_TOINT option of `lj_strscan_scan()`
        of                                        the
> and cast value to integer with losing information about its sign.
    a    of the
> 
> This patch adds special checks for these corner cases during strscan.
                                                             The
> 
> Sergey Kaplun:
> * added the description and the test for the problem
> 
> Part of tarantool/tarantool#6548
> ---
> src/lj_strscan.c                                |  8 ++++++--
> test/tarantool-tests/lj-528-tonumber-0.test.lua | 10 ++--------
> 2 files changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/src/lj_strscan.c b/src/lj_strscan.c
> index 4e4ef6d3..11d341ee 100644
> --- a/src/lj_strscan.c
> +++ b/src/lj_strscan.c
> @@ -121,7 +121,8 @@ static StrScanFmt strscan_hex(const uint8_t *p, TValue *o,
>   /* Format-specific handling. */
>   switch (fmt) {
>   case STRSCAN_INT:
> -    if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg) {
> +    if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg &&
> +	!(x == 0 && neg)) {
>       o->i = neg ? -(int32_t)x : (int32_t)x;
>       return STRSCAN_INT;  /* Fast path for 32 bit integers. */
>     }
> @@ -498,6 +499,9 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, MSize len, TValue *o,
>       if ((opt & STRSCAN_OPT_TONUM)) {
> 	o->n = neg ? -(double)x : (double)x;
> 	return STRSCAN_NUM;
> +      } else if (x == 0 && neg) {
> +	o->n = -0.0;
> +	return STRSCAN_NUM;
>       } else {
> 	o->i = neg ? -(int32_t)x : (int32_t)x;
> 	return STRSCAN_INT;
> @@ -515,7 +519,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, MSize len, TValue *o,
>       fmt = strscan_dec(sp, o, fmt, opt, ex, neg, dig);
> 
>     /* Try to convert number to integer, if requested. */
> -    if (fmt == STRSCAN_NUM && (opt & STRSCAN_OPT_TOINT)) {
> +    if (fmt == STRSCAN_NUM && (opt & STRSCAN_OPT_TOINT) && !tvismzero(o)) {
>       double n = o->n;
>       int32_t i = lj_num2int(n);
>       if (n == (lua_Number)i) { o->i = i; return STRSCAN_INT; }
> diff --git a/test/tarantool-tests/lj-528-tonumber-0.test.lua b/test/tarantool-tests/lj-528-tonumber-0.test.lua
> index 03ba2aff..f3ad53d3 100644
> --- a/test/tarantool-tests/lj-528-tonumber-0.test.lua
> +++ b/test/tarantool-tests/lj-528-tonumber-0.test.lua
> @@ -1,15 +1,9 @@
> local tap = require('tap')
> 
> --- Test disabled for DUALNUM mode default for some arches.
> --- See also https://github.com/LuaJIT/LuaJIT/pull/787.
> -require("utils").skipcond(
> -  jit.arch ~= "x86" and jit.arch ~= "x64",
> -  jit.arch.." in DUALNUM mode is clumsy for now"
> -)
> -
> -- Test file to demonstrate LuaJIT `tonumber('-0')` incorrect
> -- behaviour.
> --- See also https://github.com/LuaJIT/LuaJIT/issues/528.
> +-- See also https://github.com/LuaJIT/LuaJIT/issues/528,
> +-- https://github.com/LuaJIT/LuaJIT/pull/787.
> local test = tap.test('lj-528-tonumber-0')
> test:plan(1)
> 
> -- 
> 2.34.1
>