Re: [RFC PATCH] configure: Poison (almost) all target-specific #defines

[Thomas Huth <thuth@redhat.com>]

On 15/03/2021 19.24, Eric Blake wrote:
> On 3/15/21 8:54 AM, Thomas Huth wrote:
>> We are generating a lot of target-specific defines in the *-config-devices.h
>> and *-config-target.h files. Using them in common code is wrong and leads
>> to very subtle bugs since a "#ifdef CONFIG_SOMETHING" is not working there
>> as expected. To avoid these issues, we are already poisoning some of the
>> macros in include/exec/poison.h - but maintaining this list manually is
>> cumbersome. Thus let's generate the list of poisoned macros automatically
>> instead.
>> Note that CONFIG_TCG (which is also defined in config-host.h) and
>> CONFIG_USER_ONLY are special, so we have to filter these out.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>   RFC since the shell stuff in "configure" is quite ugly ... maybe there's
>>   a better way to do this via meson, but my meson-foo is still lacking...
>>
> 
>> +++ b/configure
>> @@ -6441,6 +6441,11 @@ if test -n "${deprecated_features}"; then
>>       echo "  features: ${deprecated_features}"
>>   fi
>>   
>> +cat *-config-devices.h *-config-target.h | grep '^#define '  \
>> +    | grep -v CONFIG_TCG | grep -v CONFIG_USER_ONLY \
>> +    | sed -e 's/#define //' -e 's/ .*//' | sort -u \
>> +    | sed -e 's/^/#pragma GCC poison /' > config-poison.h
> 
> Most times, a 'grep | sed' pipeline can be rewritten in pure sed.  In
> this case:
> 
> cat *-config-devices.h *-config-target.h | \
>    sed -n -e '/^#define / { s///; /CONFIG_TCG/d; /CONFIG_USER_ONLY/d;' \
>           -e 's/ .*//; s/^/#pragma GCC poison /p; }' | \
>    sort -u > config-poison.h

Thanks! I'll update my patch and use your suggestion (unless someone comes 
up with some Meson magic to do it there instead)

  Thomas