@qqtang to correct my questions I put them in reply:

For "build qt-base application for <target machine> on <build machine>", what should I do on both side machine?

For “prepare qt development environment by building from source for <target machine> on <build machine>", what should I do on both side machine?

@glassez Well, brief is brief. That's what I said. After all, connect returns a boolean result, to tell (briefly) if it has succeeded or failed. Deliberate and consequent ignorance of such results in class constructors is a gamble. If you believe that the reason may be OpenWRT, so be it. I tend to believe in (and briefly summarize) what I see.

@Kiruseni
honestly i dont know, i've never used nor seen this parameter until now actually.
I always used the -sysroot parameter so far.

But it seems it is set automatically anyways. I assume it just means that the compiler handles the sysroot (which gcc is capable of)

@morteza-ali-ahmadi I'm not an Android expert. Maybe somebody else knows more.

AFAIK, the BPI is very close to the Raspberry Pi, you should take a look at this wiki entry.

By the way, why are you trying to build an outdated version of Qt ? The current LTS is the 5.9 series with 5.12 around the corner.

friend tell me what should I do, really apt get can put qt or you built from src, and direct me if I need this thing for developers, where to put the sources, I have arm64 linux @bruce_the_great