Re: [Qemu-trivial] [PATCH] Remove config-devices.mak on 'make clean'

[Paolo Bonzini]

On 17/05/2016 13:27, Peter Maydell wrote:
> Our dependency mechanism works like this:
>  * on first build there is neither a .o nor a .d
>  * we create the .d as a side effect of creating the .o
>  * for rebuilds we know when we need to update the .o,
>    which also updates the .d
> 
> This system requires that you're never in a situation where there is
> a .o file but no .d (because then we will never realise we need to
> build the .d, and we will not have the dependency information about
> when to rebuild the .o).
> 
> This is working fine for our object files, but we also try to use it
> for $TARGET/config-devices.mak (where the dependency file is
> in $TARGET-config-devices.mak.d). Unfortunately "make clean" doesn't
> remove config-devices.mak, which means that it puts us in the
> forbidden situation of "object file exists but not its .d file".
> This in turn means that we will fail to notice when we need to rebuild:
>   mkdir build/depbug
>   (cd build/depbug && '../../configure')
>   make -C build/depbug -j8
>   make -C build/depbug clean
>   echo "CONFIG_CANARY = y" >> default-configs/arm-softmmu.mak
>   make -C build/depbug
>   grep CANARY build/depbug/aarch64-softmmu/config-devices.mak
> 
> The CANARY token should show up in config-devices.mak but does not.
> 
> Fix this bug by making "make clean" delete the config-devices.mak files.
> config-all-devices.mak doesn't have the same problem since it has
> no .d file, but delete it too, since it is created by "make" and
> logically should be removed by "make clean".
> 
> (Note that it is important not to remove config-devices.mak until
> after we have recursively run 'make clean' in the subdirectories.)
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Makefile b/Makefile
> index 1d076a9..a5d7e62 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -356,6 +356,7 @@ clean:
>       if test -d $$d; then $(MAKE) -C $$d $@ || exit 1; fi; \
>       rm -f $$d/qemu-options.def; \
>          done
> +     rm -f $(SUBDIR_DEVICES_MAK) config-all-devices.mak
>  
>  VERSION ?= $(shell cat VERSION)
>  
> 

Queued, thanks (and nice writeup too!)

Paolo