Long live QString::asprintf()!

asprintf() is a GNU extension that prints into a string it
allocates internally. Arguably, that's a better name for
QString::sprintf() since it also allocates memory internally.

The main problem with QString::sprintf() isn't that it's
dangerous to use (it is), but that it's not static. It also
returns a reference instead of by-value, breaking RVO.

There is a comment about removing this function completely
in Qt 6.0, but it remains the only printf-style function
in Qt that can allocate the target string, so it's vital
for logging, e.g., and the recommended replacement code
(http://linux.die.net/man/3/vsnprintf) is a nightmare.

So this patch adds static (v)asprintf() methods to replace it.

Further patches will fix up all in-tree callers and finally
deprecate the old (v)sprintf().

Test coverage is provided through the existing tests of
sprintf(), which is implemented in terms of asprintf().

Arguably, the in-tree callers show that QByteArray would
benefit from having an asprintf(), too, as most of the
in-tree code works around its lack with calls
to to{Latin1,Local8Bit}() after using the QString version.

[ChangeLog][QtCore][QString] Added asprintf(), vasprintf().

Change-Id: I8510f8d67c22230653ec0f1c252c01bc95f3c386
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/corelib/tools/qvsnprintf.cpp b/src/corelib/tools/qvsnprintf.cpp
index 2526d1cd77..e9590c3971 100644
--- a/src/corelib/tools/qvsnprintf.cpp
+++ b/src/corelib/tools/qvsnprintf.cpp
@@ -58,10 +58,10 @@ QT_BEGIN_NAMESPACE
     platforms, you should not rely on the return value or on the fact
     that you will always get a 0 terminated string back.
 
-    Ideally, you should never call this function but use QString::sprintf()
+    Ideally, you should never call this function but use QString::asprintf()
     instead.
 
-    \sa qsnprintf(), QString::sprintf()
+    \sa qsnprintf(), QString::asprintf()
 */
 
 int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
@@ -107,9 +107,9 @@ int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
 
     \warning Call this function only when you know what you are doing
     since it shows different behavior on certain platforms.
-    Use QString::sprintf() to format a string instead.
+    Use QString::asprintf() to format a string instead.
 
-    \sa qvsnprintf(), QString::sprintf()
+    \sa qvsnprintf(), QString::asprintf()
 */
 
 int qsnprintf(char *str, size_t n, const char *fmt, ...)