[OE-core] question about meta/class/qmake-base.bbclass

[Paul Eggleton]

On Monday 22 August 2011 10:42:42 Kang Kai wrote:
> When I read the file  meta/class/qmake-base.bbclass, I find that that
> are 2 lines:
>      unset QMAKESPEC || true
>      ${OE_QMAKE_QMAKE} -makefile -spec ${QMAKESPEC} -o Makefile
> $QMAKE_VARSUBST_PRE $AFTER $PROFILES $QMAKE_VARSUBST_POST || die "Error
> calling ${OE_QMAKE_QMAKE} on $PROFILES"
> 
> I am confused that why unset QMAKESPEC first and then use it a argument
> for qmake?

It's not obvious, but think that the difference here is between $QMAKESPEC and 
${QMAKESPEC} - the first one is a reference to an environment variable, the 
second is a reference to an OE/BitBake variable. So "unset QMAKESPEC" is just 
clearing out the environment variable; ${QMAKESPEC} would still have a value.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre