"Eagerly instantiate used constexpr function upon definition" broke compiling Qt #74069
Closed as not planned
Description
Since 030047c, Qt (tested with 6.6) fails to compile, with errors like this:
In file included from /home/martin/code/qt/src-6.6/src/corelib/compat/removed_api.cpp:12:
In file included from include/QtCore/qmetatype.h:1:
include/QtCore/../../../src-6.6/src/corelib/kernel/qmetatype.h:2669:1: error: explicit specialization of 'QMetaTypeId<QtMetaTypePrivate::QPairVariantInterfaceImpl>' after instantiation
2669 | QT_DECL_METATYPE_EXTERN_TAGGED(QtMetaTypePrivate::QPairVariantInterfaceImpl,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2670 | QPairVariantInterfaceImpl, Q_CORE_EXPORT)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/QtCore/../../../src-6.6/src/corelib/kernel/qmetatype.h:1361:5: note: expanded from macro 'QT_DECL_METATYPE_EXTERN_TAGGED'
1361 | Q_DECLARE_METATYPE(TYPE) \
| ^~~~~~~~~~~~~~~~~~~~~~~~
include/QtCore/../../../src-6.6/src/corelib/kernel/qmetatype.h:1504:34: note: expanded from macro 'Q_DECLARE_METATYPE'
1504 | #define Q_DECLARE_METATYPE(TYPE) Q_DECLARE_METATYPE_IMPL(TYPE)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/QtCore/../../../src-6.6/src/corelib/kernel/qmetatype.h:1508:12: note: expanded from macro 'Q_DECLARE_METATYPE_IMPL'
1508 | struct QMetaTypeId< TYPE > \
| ^~~~~~~~~~~~~~~~~~~
include/QtCore/../../../src-6.6/src/corelib/kernel/qmetatype.h:1220:22: note: implicit instantiation first required here
1220 | enum { Defined = QMetaTypeId<T>::Defined, IsBuiltIn=false };
| ^
1 error generated.
Before this commit, this file built just fine. This can be reproduced with this attached preprocessed file,
qt-preproc.zip, compiled as clang -target armv7-w64-mingw32 -c qt-preproc.cpp.
CC @cor3ntin