Qt6 build 32bit on 64bit

Redman

Hello,

to my understanding configuring a kit like followed should make it able to build 32-bit application from Qt6 64-bit.

Telling the kit to use the amd64_x86 compiler means to use a 64-bit compiler toolset to produce binaries for your program targeting a 32-bit platform afaik.

I get following error:

Redman

I found the solution thanks to @jsulm:

https://doc.qt.io/qt-6/windows-building.html#step-3-set-the-environment-variables
%SystemRoot%\system32\cmd.exe /E:ON /V:ON /k C:\Qt\qt6vars.cmd run this command in your cmd to set up the environment and KEEP the cmd OPEN. After that everything worked.

Christian Ehrlicher

If you want to built a 32bit executable all your dependent libraries are also need to be 32bit. This means you need a 32bit Qt libraries. Since there are no pre-built ones you have to compile it by your own.

But why someone would need a 32bit executable nowadays?

Redman

@Christian-Ehrlicher
I just configured the kit as shown and as you said, the linker could'nt find the corresponding 32-bit symbols.

I tried building Qt6 32-bit from source. But following error made me give up tbh.

FYI: During covid times it was impossible to get a 64-bit industrial pc so we had to settle for 32-bit for our testing environment. We deploy 64-bit for our customers.

jsulm

@Redman Did you use 32bit cmd provided by your Visual Studio set-up to have a terminal preconfigured to use Visual C++ 32bit environment?

Redman

@jsulm
Not sure how to do that.
But I called vcvarsall.bat amd64_x86 . Im not quite sure where in the toolchain the change I made is applied

jsulm

@Redman said in Qt6 build 32bit on 64bit:

the change I made is applied

What change do you mean?
Take a look at https://doc.qt.io/qt-6/windows-building.html

Redman

@jsulm I mean the vcvarsall.bat amd64_x86 change. But dont mind it.

I once again followed the guide behind the link you posted. Same result as in the screenshots

Redman

I found the solution thanks to @jsulm:

https://doc.qt.io/qt-6/windows-building.html#step-3-set-the-environment-variables
%SystemRoot%\system32\cmd.exe /E:ON /V:ON /k C:\Qt\qt6vars.cmd run this command in your cmd to set up the environment and KEEP the cmd OPEN. After that everything worked.

Christian Ehrlicher

@Redman said in Qt6 build 32bit on 64bit:

up the environment and KEEP the cmd OPEN.

Why should something you set up in one cmd instance be active in another one??

Redman

@Christian-Ehrlicher To me it seemed like a global variable that was set. Hence my assumption I could close the cmd.

JonB

@Redman
These .bat or .cmd files set environment variables. Their setting only lasts for the duration of the cmd/Command Prompt where the script file is run (and anything spawned from there, e.g. compilations), they do not persist to your machine's environment as a whole.