Deprecate q(v)snprintf()

[ChangeLog][Deprecation Notice][q(v)snprintf()] As warned in advance
in the 6.8 change-log, these functions have now been deprecated with
immediate effect. Due to an unfortunate fallback to
QString::asprintf().toLocal8Bit(), these functions introduce strictly
more platform dependencies than C++11's std::(v)snprintf(), which is
the suggested replacement.

Fixes: QTBUG-127110
Change-Id: Ieee4149ac6c4a9881e1445a77e62edd92c71b36c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qbytearrayalgorithms.h

@@ -139,11 +139,21 @@ Q_CORE_EXPORT int qstrnicmp(const char *, const char *, size_t len);
 Q_CORE_EXPORT int qstrnicmp(const char *, qsizetype, const char *, qsizetype = -1);
 
 #ifndef QT_NO_QSNPRINTF // use std::(v)snprintf() from <cstdio> instead
+#if QT_DEPRECATED_SINCE(6, 9)
+#define QSNPF_DEPR(vsn) \
+    QT_DEPRECATED_VERSION_X_6_9("Use C++11 std::" #vsn "printf() instead, taking care to " \
+                                "ensure that you didn't rely on QString::asprintf() " \
+                                "ideosyncrasies that q" #vsn "printf might, but " \
+                                "std::" #vsn "printf() does not, support.")
 // implemented in qvsnprintf.cpp
+QSNPF_DEPR(vsn)
 Q_CORE_EXPORT int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
     Q_ATTRIBUTE_FORMAT_PRINTF(3, 0);
+QSNPF_DEPR(sn)
 Q_CORE_EXPORT int qsnprintf(char *str, size_t n, const char *fmt, ...)
     Q_ATTRIBUTE_FORMAT_PRINTF(3, 4);
+#undef QSNPF_DEPR
+#endif // QT_DEPRECATED_SINCE(6, 9)
 #endif // QT_NO_QSNPRINTF
 
 // qChecksum: Internet checksum

src/corelib/text/qvsnprintf.cpp

@@ -22,15 +22,15 @@ QT_BEGIN_NAMESPACE
     \sa qsnprintf(), qvsnprintf().
 */
 
+#if QT_DEPRECATED_SINCE(6, 9)
+
 #if !defined(QT_VSNPRINTF) || defined(Q_QDOC)
 
 /*!
     \fn int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
     \relates QByteArray
 
-    \obsolete
+    \deprecated [6.9] Use C++11's \c{std::vsnprintf()} from \c{<cstdio>} instead.
-
-    Use C++11's \c{std::vsnprintf()} from \c{<cstdio>} instead.
 
     A portable \c vsnprintf() function. Will call \c ::vsnprintf(), \c
     ::_vsnprintf(), or \c ::vsnprintf_s depending on the system, or
@@ -89,9 +89,7 @@ int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
     \target bytearray-qsnprintf
     \relates QByteArray
 
-    \obsolete
+    \deprecated [6.9] Use C++11's \c{std::snprintf()} from \c{<cstdio>} instead.
-
-    Use C++11's \c{std::snprintf()} from \c{<cstdio>} instead.
 
     A portable snprintf() function, calls qvsnprintf.
 
@@ -111,10 +109,14 @@ int qsnprintf(char *str, size_t n, const char *fmt, ...)
     va_list ap;
     va_start(ap, fmt);
 
+    QT_IGNORE_DEPRECATIONS(
     int ret = qvsnprintf(str, n, fmt, ap);
+    )
     va_end(ap);
 
     return ret;
 }
 
+#endif // QT_DEPRECATED_SINCE(6, 9)
+
 QT_END_NAMESPACE

tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp

@@ -40,7 +40,9 @@ private slots:
     void base64();
     void fromBase64_data();
     void fromBase64();
+#if QT_DEPRECATED_SINCE(6, 9)
     void qvsnprintf();
+#endif
     void qstrlen();
     void qstrnlen();
     void qstrcpy();
@@ -679,6 +681,9 @@ void tst_QByteArray::fromBase64()
     }
 }
 
+#if QT_DEPRECATED_SINCE(6, 9)
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_DEPRECATED
 void tst_QByteArray::qvsnprintf()
 {
     char buf[20];
@@ -723,6 +728,8 @@ void tst_QByteArray::qvsnprintf()
     QT_WARNING_POP
 #endif
 }
+QT_WARNING_POP
+#endif // QT_DEPRECATED_SINCE(6, 9)
 
 
 void tst_QByteArray::qstrlen()