Port qt_doubleToAscii to qsizetype

Allows central handling of large buffers.

Adjust some callers.

Task-number: QTBUG-103531
Change-Id: Ib55974c3de250883cd0f6d11a7eee051c7fd11bc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit bd43c245e8c641c3a5c86762647f99658167b4db)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 12 insertions, 5 deletions

diff --git a/src/corelib/text/qlocale.cpp b/src/corelib/text/qlocale.cpp
index 73ceecb627..9e689a4fd0 100644
--- a/src/corelib/text/qlocale.cpp
+++ b/src/corelib/text/qlocale.cpp
@@ -3567,7 +3567,7 @@ QString QLocaleData::doubleToString(double d, int precision, DoubleForm form,
         width = 0;
 
     int decpt;
-    int bufSize = 1;
+    qsizetype bufSize = 1;
     if (precision == QLocale::FloatingPointShortest)
         bufSize += std::numeric_limits<double>::max_digits10;
     else if (form == DFDecimal && qIsFinite(d))
diff --git a/src/corelib/text/qlocale_tools.cpp b/src/corelib/text/qlocale_tools.cpp
index 516377c5c5..ccfcbcfa5a 100644
--- a/src/corelib/text/qlocale_tools.cpp
+++ b/src/corelib/text/qlocale_tools.cpp
@@ -75,7 +75,8 @@ QT_BEGIN_NAMESPACE
 
 QT_CLOCALE_HOLDER
 
-void qt_doubleToAscii(double d, QLocaleData::DoubleForm form, int precision, char *buf, int bufSize,
+void qt_doubleToAscii(double d, QLocaleData::DoubleForm form, int precision,
+                      char *buf, qsizetype bufSize,
                       bool &sign, int &length, int &decpt)
 {
     if (bufSize == 0) {
@@ -129,7 +130,12 @@ void qt_doubleToAscii(double d, QLocaleData::DoubleForm form, int precision, cha
     } else {
         mode = double_conversion::DoubleToStringConverter::FIXED;
     }
-    double_conversion::DoubleToStringConverter::DoubleToAscii(d, mode, precision, buf, bufSize,
+    // libDoubleConversion is limited to 32-bit lengths. It's ok to cap the buffer size,
+    // though, because the library will never write 2GiB of chars as output
+    // (the length out-parameter is just an int, too).
+    const auto boundedBufferSize = static_cast<int>((std::min)(bufSize, qsizetype(INT_MAX)));
+    double_conversion::DoubleToStringConverter::DoubleToAscii(d, mode, precision, buf,
+                                                              boundedBufferSize,
                                                               &sign, &length, &decpt);
 #else // QT_NO_DOUBLECONVERSION || QT_BOOTSTRAPPED
 
@@ -619,7 +625,7 @@ QString qdtoa(qreal d, int *decpt, int *sign)
     int length = 0;
 
     // Some versions of libdouble-conversion like an extra digit, probably for '\0'
-    constexpr int digits = std::numeric_limits<double>::max_digits10 + 1;
+    constexpr qsizetype digits = std::numeric_limits<double>::max_digits10 + 1;
     char result[digits];
     qt_doubleToAscii(d, QLocaleData::DFSignificantDigits, QLocale::FloatingPointShortest,
                      result, digits, nonNullSign, length, nonNullDecpt);
diff --git a/src/corelib/text/qlocale_tools_p.h b/src/corelib/text/qlocale_tools_p.h
index a4dbcf209b..27d5cdfd78 100644
--- a/src/corelib/text/qlocale_tools_p.h
+++ b/src/corelib/text/qlocale_tools_p.h
@@ -65,7 +65,8 @@ enum StrayCharacterMode {
 // API note: this function can't process a number with more than 2.1 billion digits
 [[nodiscard]] double qt_asciiToDouble(const char *num, qsizetype numLen, bool &ok, int &processed,
                                       StrayCharacterMode strayCharMode = TrailingJunkProhibited);
-void qt_doubleToAscii(double d, QLocaleData::DoubleForm form, int precision, char *buf, int bufSize,
+void qt_doubleToAscii(double d, QLocaleData::DoubleForm form, int precision,
+                      char *buf, qsizetype bufSize,
                       bool &sign, int &length, int &decpt);
 
 [[nodiscard]] QString qulltoBasicLatin(qulonglong l, int base, bool negative);