[Interest] building Qt 4.8.7 with gcc 5 and link-time optimisation on Linux

René J. V. Bertin rjvbertin at gmail.com
Fri Jul 24 14:23:08 CEST 2015

René J. V. Bertin wrote:

>> That shouldn't happen. QT_COMPILER_SUPPORTS_SSE4_2 should not be defined, so
>> this wouldn't evaluate to true:
> That's what I figured and that's why I tried the options. I'll see if I can
> reproduce the issue and report back.

Sadly, I can. I cannot find any definition of QT_COMPILER_SUPPORTS_SSE4_2 (is it 
maybe generated dynamically?!). I checked, it's not auto-vectorised code by the 
compiler that uses SSE4, but indeed that block of code in qhash.cpp that 
shouldn't be included with -mno-sse4.2 . I'm a bit at a loss re: how to debug 
this. I'm guessing that you'd have noticed if clang didn't handle macros like 


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