Sven Baars : oleaut32: Use scientific notation if it prevents a loss of accuracy.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 8a8d1dedcf1229abb0fd90b93a8beae7765af5fd
URL:    https://gitlab.winehq.org/wine/wine/-/commit/8a8d1dedcf1229abb0fd90b93a8beae...

Author: Sven Baars <sbaars(a)codeweavers.com>
Date:   Sat Feb 24 21:11:17 2024 +0100

oleaut32: Use scientific notation if it prevents a loss of accuracy.

---

 dlls/oleaut32/tests/vartype.c | 22 ++++++++++++++++------
 dlls/oleaut32/vartype.c       | 14 +++++++++++---
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/dlls/oleaut32/tests/vartype.c b/dlls/oleaut32/tests/vartype.c
index 795446d0987..8516689d1bd 100644
--- a/dlls/oleaut32/tests/vartype.c
+++ b/dlls/oleaut32/tests/vartype.c
@@ -4679,12 +4679,22 @@ static void test_VarBstrFromR8(void)
 {
   static const struct r8_test tests_en[] =
   {
-    { 0.5, L"0.5" },
-    { 0.05, L"0.05" },
-    { 0.005, L"0.005" },
-    { 0.0005, L"0.0005" },
-    { 0.00005, L"0.00005" },
-    { 0.000005, L"0.000005" },
+    { 0.56789, L"0.56789" },
+    { 5.6789e-2, L"0.056789" },
+    { 5.6789e-3, L"0.0056789" },
+    { 5.6789e-4, L"0.00056789" },
+    { 5.6789e-5, L"0.000056789" },
+    { 5.6789e-6, L"0.0000056789" },
+    { 5.6789e-7, L"0.00000056789" },
+    { 5.6789e-8, L"0.000000056789" },
+    { 5.6789e-9, L"0.0000000056789" },
+    { 5.6789e-10, L"0.00000000056789" },
+    { 5.6789e-11, L"0.000000000056789" },
+    { 5.6789e-12, L"5.6789E-12" },
+    { 5.6789e-13, L"5.6789E-13" },
+    { 5.6789e-14, L"5.6789E-14" },
+    { 5.6789e-15, L"5.6789E-15" },
+    { 5.6789e-16, L"5.6789E-16" },
 
     { 1.0e8, L"100000000" },
     { 1.0e12, L"1000000000000" },
diff --git a/dlls/oleaut32/vartype.c b/dlls/oleaut32/vartype.c
index d11fb41d1b3..747705f94e2 100644
--- a/dlls/oleaut32/vartype.c
+++ b/dlls/oleaut32/vartype.c
@@ -6550,10 +6550,18 @@ static HRESULT VARIANT_BstrFromReal(DOUBLE dblIn, LCID lcid, ULONG dwFlags,
   if (!(locale = _create_locale(LC_ALL, "C"))) return E_OUTOFMEMORY;
   len = _swprintf_l(buff, ARRAY_SIZE(buff), L"%.*G", locale, ndigits, dblIn);
   e = wcschr(buff, 'E');
-  if (e && labs(wcstol(e+1, NULL, 10)) < ndigits)
+  if (e)
   {
-    len = _swprintf_l(buff, ARRAY_SIZE(buff), L"%.*f", locale, ndigits, dblIn);
-    while (len > 0 && (buff[len-1] == '0')) len--;
+      int extra_decimals;
+      WCHAR *dot;
+
+      dot = wcschr(buff, '.');
+      extra_decimals = dot ? e - dot - 2 : 0;
+      if (labs(wcstol(e+1, NULL, 10)) + extra_decimals < ndigits)
+      {
+          len = _swprintf_l(buff, ARRAY_SIZE(buff), L"%.*f", locale, ndigits, dblIn);
+          while (len > 0 && (buff[len-1] == '0')) len--;
+      }
   }
   buff[len] = 0;
   _free_locale(locale);