Hello,

Platform: AArch64 Linux with Clang as a compiler. On this particular example I'm on Fedora 41 (Asahi Linux).

Due to this long-standing LLVM issue – https://github.com/llvm/llvm-project/issues/16778 ; https://reviews.llvm.org/D141836  – it is not possible to use int128 on many AArch64 platforms when using ubsan, as this generates calls to symbols not implemented by the platform's libgcc (which may be desireable to use when linking against system libraries), such as __muloti4 

Sadly, trying to disable int128 support with  -DQT_NO_INT128 now yields, since qtbase@feb43b779ac

qtbase/src/corelib/global/qtypes.cpp:508:4: error: Qt needs to be compiled in a mode that enables INT128     if the compiler supports it in principle. 
 508 | #  error Qt needs to be compiled in a mode that enables INT128 \ 
     |    ^ 

Thus this is between a rock and a hard place with no proper way to build.