[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>
---
 dlls/msvcrt/math.c         | 24 ++++++++++++++++++++----
 dlls/msvcrt/tests/printf.c |  4 ++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 6b2d08a8294..cdc93a6b75a 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -2588,6 +2588,10 @@ char * CDECL _ecvt( double number, int ndigits, int *decpt, int *sign )
     if( number < 0) {
         *sign = TRUE;
         number = -number;
+    } else if(number == 0) {
+        /* handle negative zero correctly */
+        *sign = signbit(number) ? TRUE : FALSE;
+        number = 0;
     } else
         *sign = FALSE;
     /* handle cases with zero ndigits or less */
@@ -2651,6 +2655,10 @@ int CDECL _ecvt_s( char *buffer, size_t length, double number, int ndigits, int
     if( number < 0) {
         *sign = TRUE;
         number = -number;
+    } else if(number == 0) {
+        /* handle negative zero correctly */
+        *sign = signbit(number) ? TRUE : FALSE;
+        number = 0;
     } else
         *sign = FALSE;
     len = _snprintf(result, prec + 7, "%.*le", prec - 1, number);
@@ -2692,8 +2700,12 @@ char * CDECL _fcvt( double number, int ndigits, int *decpt, int *sign )
 
     if (number < 0)
     {
-	*sign = 1;
-	number = -number;
+        *sign = 1;
+        number = -number;
+    } else if(number == 0) {
+        /* handle negative zero correctly */
+        *sign = signbit(number) ? 1 : 0;
+        number = 0;
     } else *sign = 0;
 
     stop = _snprintf(buf, 80, "%.*f", ndigits < 0 ? 0 : ndigits, number);
@@ -2776,8 +2788,12 @@ int CDECL _fcvt_s(char* outbuffer, size_t size, double number, int ndigits, int
 
     if (number < 0)
     {
-	*sign = 1;
-	number = -number;
+        *sign = 1;
+        number = -number;
+    } else if(number == 0) {
+        /* handle negative zero correctly */
+        *sign = signbit(number) ? 1 : 0;
+        number = 0;
     } 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