Re: [Qemu-devel] [PULL 04/16] Makefile: Rules for docker testing

[Paolo Bonzini <pbonzini@redhat.com>]

On 06/06/2016 17:02, Eduardo Habkost wrote:
> On Mon, Jun 06, 2016 at 04:32:50PM +0200, Paolo Bonzini wrote:
>> On 06/06/2016 16:15, Eduardo Habkost wrote:
>>>>> No, the second time you'll get the expansion of
>>>>>
>>>>> DOCKER_SRC_COPY := docker-src.$(CUR_TIME)
>>> And why it isn't enough to simply write the above line in the
>>> Makefile without any eval trick?
>>
>> Because 1) initially the idea was to delay the $(mkdir) too 2) Too many
>> $(shell) end up slowing down make.
> 
> Now I see: you wanted to delay the shell command, but evaluate it
> only once.
> 
> But I don't see why it makes sense here, because the variable is
> being expanded immediately after it is defined (in the
> "$(DOCKER_SRC_COPY):" line), and CUR_TIME is already defined
> using ":=".

Well, when I proposed the eval trick CUR_TIME was defined with "=". :)

I agree that right now it's all unnecessary.

Paolo