[PATCH] msvcrt: Handle negative zero (-0.0) in _ecvt and others.

[Lauri Kenttä]

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=50885
Signed-off-by: Lauri Kenttä <lauri.kentta(a)gmail.com>

---
v2: More compact version.

 dlls/msvcrt/math.c         | 18 ++++++++----------
 dlls/msvcrt/tests/printf.c |  4 ++++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 6b2d08a8294..eb25b578a2b 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -2585,7 +2585,7 @@ char * CDECL _ecvt( double number, int ndigits, int *decpt, int *sign )
     if (!data->efcvt_buffer)
         data->efcvt_buffer = malloc( 80 ); /* ought to be enough */
 
-    if( number < 0) {
+    if (number < 0 || (number == 0 && signbit(number))) {
         *sign = TRUE;
         number = -number;
     } else
@@ -2648,7 +2648,7 @@ int CDECL _ecvt_s( char *buffer, size_t length, double number, int ndigits, int
     if( prec < 1) prec = 2;
     result = malloc(prec + 7);
 
-    if( number < 0) {
+    if (number < 0 || (number == 0 && signbit(number))) {
         *sign = TRUE;
         number = -number;
     } else
@@ -2690,10 +2690,9 @@ char * CDECL _fcvt( double number, int ndigits, int *decpt, int *sign )
     if (!data->efcvt_buffer)
         data->efcvt_buffer = malloc( 80 ); /* ought to be enough */
 
-    if (number < 0)
-    {
-	*sign = 1;
-	number = -number;
+    if (number < 0 || (number == 0 && signbit(number))) {
+        *sign = 1;
+        number = -number;
     } else *sign = 0;
 
     stop = _snprintf(buf, 80, "%.*f", ndigits < 0 ? 0 : ndigits, number);
@@ -2774,10 +2773,9 @@ int CDECL _fcvt_s(char* outbuffer, size_t size, double number, int ndigits, int
         return EINVAL;
     }
 
-    if (number < 0)
-    {
-	*sign = 1;
-	number = -number;
+    if (number < 0 || (number == 0 && signbit(number))) {
+        *sign = 1;
+        number = -number;
     } else *sign = 0;
 
     stop = _snprintf(buf, 80, "%.*f", ndigits < 0 ? 0 : ndigits, number);
diff --git a/dlls/msvcrt/tests/printf.c b/dlls/msvcrt/tests/printf.c
index 8960671f23e..14fd75d2b3c 100644
--- a/dlls/msvcrt/tests/printf.c
+++ b/dlls/msvcrt/tests/printf.c
@@ -647,6 +647,10 @@ static struct {
     {           0.0,   5,     "00000",          "00000",          0,      0,     0 },
     {           0.0,   0,          "",               "",          0,      0,     0 },
     {           0.0,  -1,          "",               "",          0,      0,     0 },
+    /* -0.0 with different precisions */
+    {          -0.0,   5,     "00000",          "00000",          0,      0,     1 },
+    {          -0.0,   0,          "",               "",          0,      0,     1 },
+    {          -0.0,  -1,          "",               "",          0,      0,     1 },
     /* Numbers > 1.0 with 0 or -ve precision */
     {     -123.0001,   0,          "",            "123",          3,      3,     1 },
     {     -123.0001,  -1,          "",             "12",          3,      3,     1 },
-- 
2.31.0

[Piotr Caban]

Hi Lauri,

I've sent modified version of your patch (so it also handles e.g. -NAN):
https://source.winehq.org/patches/data/203047

Thanks,
Piotr

[Lauri Kenttä]

On 2021-04-01 22:00, Piotr Caban wrote:
> Hi Lauri,
>
> I've sent modified version of your patch (so it also handles e.g. 
> -NAN):
> https://source.winehq.org/patches/data/203047

Looks good! I was focused only on my own use case, but evidently there 
was a lot more to do.

It's nice to send occasional patches when the response is so helpful and 
constructive. Thanks to all wine-devel people who make this happen.

-- 
Lauri