The use of QT_OVERLOADED_MACRO combined with pedantic warnings would
result in
warning: must specify at least one argument for '...' parameter of
variadic macro [-Wgnu-zero-variadic-macro-arguments]
when used with a single argument, as the QT_VA_ARGS_COUNT macro would
end up not passing anything to the last ... argument of the helper macro
QT_VA_ARGS_CHOOSE.
To work around this we extend the arguments passed to QT_VA_ARGS_CHOOSE
by one, adding a zero-count, so that the variadic parameter always has
at least one argument.
Unfortunately this doesn't give us a count of 0 if a overloaded Qt macro
is used without arguments, due to __VA_ARGS__ always being treated as an
argument to QT_VA_ARGS_CHOOSE, even when empty, due to the comma after it.
The result is that we end up calling the 1-argument macro for this case
as well.
Getting a correct zero-count, for both MSVC and GCC/Clang, without using
GCC extensions, is quite involved, so we're opting to live with this
limitation. See https://stackoverflow.com/a/62183700 for details.
Fixes: QTBUG-93750
Pick-to: 6.1
Change-Id: Ib7b26216f36a639642a70387e0d73223633ba6b6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
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