[Qemu-devel] Re: [PATCH] Makefile: Update unmodified config-devices.mak automatically

[Stefan Weil]

Michael S. Tsirkin schrieb:
> On Sun, Dec 20, 2009 at 03:39:03PM +0100, Stefan Weil wrote:
>   
>> This makes rebuilds after source updates easier
>> for most users (who don't edit config-devices.mak).
>>
>> Signed-off-by: Stefan Weil <address@hidden>
>>     
>
> Sorry about missing this and not commenting earlier.
>
> So the problem here is that it relies on keeping
> .old file around. This is a generated file, but
> - you don't remove it with make clean or distclean
>   

As long as config-devices.mak is not removed,
config-devices.mak.old has to be kept, too.

> - it is not removed on error properly as it is not
>   a target of makefile
> so it seems easy to get into a situation where
> a corrupted file will be created and the only way
> to get rid of it would be by manual rm command.
>   

I don't think that this is a real world scenario.
The .old file is a simple copy of config-devices.mak.

> Instead, what I think we should do is make
> the generated file *almost empty*
> and then it is easy to detect user tweaking
> it without keeping more state.
>   

This is a matter of personal preferences.
Maybe other users who want to modify
config-devices.mak prefer to have a full
version where they can remove some lines
they don't need.

The solution implemented here was the result
of Juan's feedback to an earlier suggestion
from me.

> A patch I posted does this by sticking
> a single "include" directive in a generated file.
>
>
>   
>> ---
>>  Makefile |   20 +++++++++++++++-----
>>  1 files changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/Makefile b/Makefile
>> index c1fa08c..684365d 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -43,12 +43,22 @@ config-all-devices.mak: $(SUBDIR_DEVICES_MAK)
>>  
>>  %/config-devices.mak: default-configs/%.mak
>>      $(call quiet-command,cat $< > address@hidden, "  GEN   $@")
>> -    @if test -f $@ ; then \
>> -      echo "WARNING: $@ out of date." ;\
>> -      echo "Run \"make defconfig\" to regenerate." ; \
>> -      rm address@hidden ; \
>> +    @if test -f $@; then \
>> +      if cmp -s address@hidden $@ || cmp -s $@ address@hidden; then \
>> +        mv address@hidden $@; \
>> +        cp -p $@ address@hidden; \
>> +      else \
>> +        if test -f address@hidden; then \
>> +          echo "WARNING: $@ (user modified) out of date.";\
>> +        else \
>> +          echo "WARNING: $@ out of date.";\
>> +        fi; \
>> +        echo "Run \"make defconfig\" to regenerate."; \
>> +        rm address@hidden; \
>> +      fi; \
>>       else \
>> -      mv address@hidden $@ ; \
>> +      mv address@hidden $@; \
>> +      cp -p $@ address@hidden; \
>>       fi
>>  
>>  defconfig:
>> -- 
>> 1.6.5