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| author | Tor Arne Vestbø <tor.arne.vestbo@qt.io> | 2021-05-18 17:35:40 +0200 |
|---|---|---|
| committer | Tor Arne Vestbø <tor.arne.vestbo@qt.io> | 2021-05-18 19:07:51 +0000 |
| commit | 0855f6279182af9cb54ac5113ba5c99db8ecb819 (patch) | |
| tree | 38642474ba7946e3d80516ce54a729f1ae5036c1 /src/corelib/global/qglobal.h | |
| parent | f2d26f95fe12fe66ea1d30cf6205b667de1b9fb2 (diff) | |
Fix single argument QT_OVERLOADED_MACRO with pedantic warnings enabled
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>
Diffstat (limited to 'src/corelib/global/qglobal.h')
| -rw-r--r-- | src/corelib/global/qglobal.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h index 481ee695ca..16bcb14e7d 100644 --- a/src/corelib/global/qglobal.h +++ b/src/corelib/global/qglobal.h @@ -1397,7 +1397,7 @@ inline int qIntCast(float f) { return int(f); } #define QT_VA_ARGS_CHOOSE(_1, _2, _3, _4, _5, _6, _7, _8, _9, N, ...) N #define QT_VA_ARGS_EXPAND(...) __VA_ARGS__ // Needed for MSVC -#define QT_VA_ARGS_COUNT(...) QT_VA_ARGS_EXPAND(QT_VA_ARGS_CHOOSE(__VA_ARGS__, 9, 8, 7, 6, 5, 4, 3, 2, 1)) +#define QT_VA_ARGS_COUNT(...) QT_VA_ARGS_EXPAND(QT_VA_ARGS_CHOOSE(__VA_ARGS__, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)) #define QT_OVERLOADED_MACRO_EXPAND(MACRO, ARGC) MACRO##_##ARGC #define QT_OVERLOADED_MACRO_IMP(MACRO, ARGC) QT_OVERLOADED_MACRO_EXPAND(MACRO, ARGC) #define QT_OVERLOADED_MACRO(MACRO, ...) QT_VA_ARGS_EXPAND(QT_OVERLOADED_MACRO_IMP(MACRO, QT_VA_ARGS_COUNT(__VA_ARGS__))(__VA_ARGS__)) |