QAudioHelpers: fix C++20 -Werror,-Wdeprecated-enum-float-conversion

Says Clang 10.0.0 -std=c++20:

qaudiohelpers.cpp:71:44: error: arithmetic between enumeration type 'QAudioHelperInternal::signedVersion<unsigned char>::(anonymous enum at /home/marc/Qt/qt5/qtmultimedia/src/multimedia/audio/qaudiohelpers.cpp:63:5)' and floating-point type 'double' is deprecated [-Werror,-Wdeprecated-enum-float-conversion]
        pDst[i] = signedVersion<T>::offset + ((typename signedVersion<T>::TS)(pSrc[i] - signedVersion<T>::offset) * factor);
                  ~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix by turning the enum { offset } into a static constexpr int
instead.

Manual conflict resolutions:
  - extended the fix to the Qt5-only quint{16,32} specializations
    which are missing from the Qt 6 code. For the quint32 code,
    chose uint as decltype(offset), because 0x8000'0000 is not a
    proper value for int, and the subtraction for which offset is
    used doesn't promote its arguents to int, like for quint{8,16},
    but stays in uint space, so an uint offset is suitable.

Task-number: QTBUG-104172
Change-Id: I92a22583fc5e1fc524364b64701aa8d416b82671
Reviewed-by: Lars Knoll <lars.knoll@gmail.com>
(cherry picked from commit 94d43085b3f3327b2bf2d644c5f984391f608d3a)
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/multimedia/audio/qaudiohelpers.cpp b/src/multimedia/audio/qaudiohelpers.cpp
index aba4ae38f..2e31286d7 100644
--- a/src/multimedia/audio/qaudiohelpers.cpp
+++ b/src/multimedia/audio/qaudiohelpers.cpp
@@ -103,19 +103,19 @@ template<class T> struct signedVersion {};
 template<> struct signedVersion<quint8>
 {
     typedef qint8 TS;
-    enum {offset = 0x80};
+    static constexpr int offset = 0x80;
 };
 
 template<> struct signedVersion<quint16>
 {
     typedef qint16 TS;
-    enum {offset = 0x8000};
+    static constexpr int offset = 0x8000;
 };
 
 template<> struct signedVersion<quint32>
 {
     typedef qint32 TS;
-    enum {offset = 0x80000000};
+    static constexpr uint offset = 0x80000000;
 };
 
 template<class T> void adjustUnsignedSamples(qreal factor, const void *src, void *dst, int samples)