QMimeTypeParser: don't use the heap to create QMimeMagicRules

The function createMagicMatchRule() returned a heap-allocated
QMimeMagicRule, and the caller code did not check the return
value for nullptr, but copied the rule into a container before
deleting the original again.

Fix by returning by-value instead. Every C++ compiler will
use RVO for this. On top, add an optimistic std::move()
when inserting the rule into the container (currently QList,
so no rvalue-push_back, yet).

While touching the return value, also remove an unholy
out-parameter with just local effects by returning a Result
struct instead. The rest of the code remains full of out-
parameters, of course.

Add one Q_UNLIKELY and two qUtf16Printable() as drive-bys.

Saves ~300b in text size on optimized GCC 5.3 Linux AMD64
builds.

Change-Id: I4374ab41f38502cd5c64ac37d106ca4bc6e00327
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

0 files changed, 0 insertions, 0 deletions