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Re: [Qemu-devel] [PATCH] Makefile: Don't build generated headers before


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH] Makefile: Don't build generated headers before Makefile is reread
Date: Fri, 4 Jul 2014 15:33:52 +0100

On 30 June 2014 13:09, Paolo Bonzini <address@hidden> wrote:
> Il 28/06/2014 18:59, Peter Maydell ha scritto:
>
>> Having a direct dependency
>>    Makefile: $(GENERATED_HEADERS)
>> can result in not-from-clean builds failing sometimes, because it means
>> that when Make does its "is any makefile or include out of date and
>> needing a rebuild?" check, as well as possibly running configure (to
>> update config-host.mak) it will also rebuild GENERATED_HEADERS under
>> the "old" config-host.mak regime. If the makefile rules for rebuilding
>> the generated headers have changed in a way that means they're not
>> compatible with the old config-host.mak variable names, the build will
>> fail. Even if it does work, it's wasted effort since we'll need to
>> rebuild them with the right config-host.mak settings immediately.
>>
>> Instead, make the generated headers depend on config-host.mak
>> and config-target.mak. This means we'll definitely rebuild them
>> if the configuration changes, but it will be done after Make
>> reloads its makefiles and includes so will happen with the
>> correct set of config-host.mak settings.
>>
>> We rely on the various .o files having correct autogenerated
>> dependency rules to cause the generated headers to be generated
>> as and when they are needed.

> Reviewed-by: Paolo Bonzini <address@hidden>


Any objections to this going into 2.1 for rc1 ?

-- PMM



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