On Wednesday 22 July 2015 21:57:57 René J. V. Bertin wrote: > > qtbase: > > ./configure [...] > > qmake -config ltcg > > When was that syntax introduced? I'm getting an error trying it even with > qmake 5.4.2 .
$ git name-rev --tags 1bd27f24fb7f7d82f4b67cffe43e0af644709106 1bd27f24fb7f7d82f4b67cffe43e0af644709106 tags/v5.4.0-alpha1~525 It should work on 5.4 then. The fix for static libraries came with 5.4.1, though. Check if you have mkspecs/features/ltcg.prf. > > Does it work? Yes, my GCC release build of Qt has been done with LTCG for > > two years. > > And is there a noticeable effect (apart from a measurable one)? It takes noticeably longer to compile :-) Well, not everything. qmake, for example, is faster to compile with -flto -fno- fat-lto-objects than without. But that's the exception, not the rule. Similarly, the bootstrapped binaries (qmake, moc, rcc) are smaller, despite the use of -ffunction-sections -Wl,--gc-sections. The libraries are bigger, but that might be due to my use of -O3 (causes code expansion). I run Creator with this build (and also compile it in LTO mode), but I have no point of comparison. If I can't run this Creator build, it's because I broke something and then I need to use the debug version. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
