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QT_INLINE_SINCE: never inline for static Qt builds

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Static Qt builds are not covered by BC guarantees, but since all
'libraries' are linked into a single executable, we face in all users
of the library the same ODR violation that we faced within the
implementation DLL: we can't define the same symbol as inline in some
TUs and out-of-line in others.

In the past, we decided to always inline in static builds, but that
breaks users which, by Hyrum's Law, have come to depend on the
non-existent BC guarantees for static Qt builds.

By switching to never inline¹ in static builds, we restore BC for such
users. The performance issues should be minimal, since LTO will anyway
inline whatever it wants, independent on how it was declared.

¹ except when the deprecation point has passed over the Qt version the
  API was inlined (-disable-deprecated-up-to configure switch).

[ChangeLog][QtCore] Restored binary compatibility for static Qt
builds broken by the QT_INLINE_SINCE mechanism. Qt still does not
guarantee BC for static build configurations otherwise.

Fixes: QTBUG-109449
Change-Id: Ie3fa62621b74dc5e9dac301b9882c0e3c3999eaf
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 8602a224b6ade5680329270d8d573b786a7a81a1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Marc Mutz 2022-12-15 17:45:56 +01:00 committed by Qt Cherry-pick Bot
parent 806acc65b8
commit 7a850fc00c
1 changed files with 2 additions and 1 deletions
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3
cmake/modulecppexports.h.in
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@ -16,8 +16,9 @@
# define Q_@module_define_infix@_EXPORT
#endif
#if !defined(QT_BUILD_@module_define_infix@_LIB) || defined(QT_STATIC)
#if !defined(QT_BUILD_@module_define_infix@_LIB) && !defined(QT_STATIC)
/* outside library → inline decl + defi */
/* static builds treat everything as part of the library, so they never inline */
# define QT_@module_define_infix@_INLINE_SINCE(major, minor) inline
# define QT_@module_define_infix@_INLINE_IMPL_SINCE(major, minor) 1
#elif defined(QT_@module_define_infix@_BUILD_REMOVED_API)