... by not injecting potentially-expensive temporary objects into the
caller's stack frame.
Default arguments are a convenient way to avoid overloads, but if the
defaulted argument isn't a Trivial Type, and the common use case is
not to pass the extra argument explicitly, the construction of the
temporary can dominate the call's runtime.
Since QHash is generic code, we don't know whether T or Key are
expensive or cheap to construct, so use overloading instead of default
arguments to avoid injecting needless code into call sites.
[ChangeLog][QtCore][Potentially Source-Incompatible
Changes][QHash/QMultiHash] The value(key) and key(value) functions are
now overloaded on presence of the defaultValue (was: defaulted
argument) to avoid injecting temporary objects into the caller's stack
frame.
Task-number: QTBUG-98117
Change-Id: I80fdd5436f3de3e4bbe20242fe45916aef62ff0c
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
7fe5611365