On Thursday, 23 July 2020 13:50:26 PDT Bernhard Lindner wrote:
> I thought of something like a simple, manually maintained ABI version. Sure,
> on the one hand this wouldn't prevent uninentional BC breaks. On the other
> hand, BC changes could be done intentionally and managed in a safe way
> (without strange crashes).
We already have several.
See qhooks.cpp's qtHookData[6]:
// TypeInformationVersion, an integral value, bumped whenever private
// object sizes or member offsets that are used in Qt Creator's
// data structure "pretty printing" change.
//
// The required sizes and offsets are tested in tests/auto/other/
toolsupport.
// When this fails and the change was intentional, adjust the test and
// adjust this value here.
See QObjectPrivate::checkForIncompatibleLibraryVersion(int version).
See the ELF versioning trick, which will permit loading Qt 5 and Qt 6
(unnamespaced!) in the same process on ELF systems.
See the ability to configure Qt in a namespace and to insert an infix in the
library name. I've been using the latter for 7 years:
$ ls -1 lib/libQt5Core*
lib/libQt5Core.la
lib/libQt5Core.t.prl
lib/libQt5Core.t.so
lib/libQt5Core.t.so.5
lib/libQt5Core.t.so.5.15
lib/libQt5Core.t.so.5.15.0
That way my builds of Qt don't interfere with the Qt-based applications I have
in my desktop. It's highly annoying to fix a broken Qt when your desktop is
broken.
I don't think we need more. Want to make BIC builds? Suit yourself. Here's the
gun, the ammo and there's your foot.
At best, we could adjust: add the library infix to the ELF version and default
to an infix for any non-standard build.
symbol _ZN7QObjectC1EPS_@@Qt6.qreal_float.nonouniqueaddress
in library libQt6Core.qrealfloat.nonouniqueaddress.so.6
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel DPG Cloud Engineering
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