Official builds support for older Mac hardware (e.g. with Penryn CPUs) without certain SSE4.2 instructions

[ASentientBot]

Please provide the following information

qBittorrent version and Operating System

4.3.4.1
macOS 11.3 DP6

If on linux, libtorrent-rasterbar and Qt version

(type here)

What is the problem

The libtorrent-rasterbar.10.dylib is compiled for Nehalem and newer CPUs and uses POPCNT instruction, causing a crash on, eg. my Core 2 Duo MacBook.

What is the expected behavior

No crash.

Steps to reproduce

Open the app on a pre-2011 Mac.

Extra info(if any)

Not sure if you'd like to support the older hardware, or if this was an intentional decision to drop support. I'll try compiling from source later, or downgrading the dylib to an older version (qBittorrent 4.2.1, for example, worked fine on my machine). Probably easy to fix with a compiler flag?

Thanks for making a great app!

[FranciscoPombal]

You'll have to ask @sledgehammer999 about such details with the official macOS builds. But yes, it sounds like the kind of issue that can be fixed with a simple change to a compiler flag - hopefully that is the case.

However, I would not change it for the official builds. Targeting older architectures would almost certainly cause a performance/efficiency regression for everyone on newer hardware (since the code would not make use of the newer instructions). I don't think it is a worthwhile trade-off just to keep out-of-the-box support for such old mac hardware as those using C2D's.

As such, I'll convert this to a discussion - hopefully someone with enough knowledge about the macOS toolchain can come along and propose a solution that you can use to compile from source and produce a binary compatible with your hardware.

[ASentientBot]

Thank you for the response @FranciscoPombal! I was able to get it working by rebuilding openssl and libtorrent from source, installing them system-wide and replacing the dylibs in the app with symlinks to the installed copies. Will try downloading Qt and properly rebuilding the entire app later, but this works for now.

I wasn't sure if the new instructions provided a noticeable performance benefit, or if they were just used in a couple places. Not sure how to check that. But I certainly don't expect you guys to support decade-old hardware, and it is now working fine for me.

Thanks!