Add a macro to disable only some 8 bit/16 bit string conversions

This is an opt-in trade-off between type safety and user
code convenience.

QT_NO_CAST_FROM_ASCII is highly beneficial to avoid unintended
conversions from 8 bit data with potentially "unsuitable"
encodings to QString. However, it has the undesirable side-effect
to require user code to wrap character and string literals
in QLatin1Char(...) and QLatin1String(...) or use similar
construction, cluttering the code significantly.

This patch introduces a QT_RESTRICTED_CAST_FROM_ASCII macro
that works almost as QT_NO_CAST_FROM_ASCII, except that it
enables the QChar(char) constructor and adds an additional
QString(const char (&ch)[N]) constructor that matches
C++ string literals, but no arbitrary character pointers.
This avoids a significant share of the need to clutter the
user code by only a slight relaxation of the type-safety.

[ChangeLog][QtCore][QString] Added QT_RESTRICTED_CAST_FROM_ASCII
macro as less intrusive alternative to QT_NO_CAST_FROM_ASCII.

Change-Id: Iac72f1f90f81fbcae9bfb1fe68b0fec6ffb36c50
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/corelib/tools/qchar.h b/src/corelib/tools/qchar.h
index 4db09e0f82..dcbe3fb0c2 100644
--- a/src/corelib/tools/qchar.h
+++ b/src/corelib/tools/qchar.h
@@ -83,8 +83,10 @@ public:
 
 #ifndef QT_NO_CAST_FROM_ASCII
     QT_ASCII_CAST_WARN Q_DECL_CONSTEXPR explicit QChar(char c) : ucs(uchar(c)) { }
+#ifndef QT_RESTRICTED_CAST_FROM_ASCII
     QT_ASCII_CAST_WARN Q_DECL_CONSTEXPR explicit QChar(uchar c) : ucs(c) { }
 #endif
+#endif
     // Unicode information
 
     enum Category