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 many of the
macros in include/exec/poison.h - but it's cumbersome to maintain this
list manually. Thus let's generate an additional list of poisoned macros
automatically from the current config switches - this should give us a
much better test coverage via the different CI configurations.

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>
---
 Makefile              | 2 +-
 configure             | 5 +++++
 include/exec/poison.h | 2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index bcbbec71a1..4cab10a2a4 100644
--- a/Makefile
+++ b/Makefile
@@ -213,7 +213,7 @@ qemu-%.tar.bz2:
 
 distclean: clean
 	-$(quiet-@)test -f build.ninja && $(NINJA) $(NINJAFLAGS) -t clean -g || :
-	rm -f config-host.mak config-host.h*
+	rm -f config-host.mak config-host.h* config-poison.h
 	rm -f tests/tcg/config-*.mak
 	rm -f config-all-disas.mak config.status
 	rm -f roms/seabios/config.mak roms/vgabios/config.mak
diff --git a/configure b/configure
index 4f374b4889..a0f0601e7e 100755
--- a/configure
+++ b/configure
@@ -6440,6 +6440,11 @@ if test -n "${deprecated_features}"; then
     echo "  features: ${deprecated_features}"
 fi
 
+sed -n -e '/CONFIG_TCG/d' -e '/CONFIG_USER_ONLY/d' \
+    -e '/^#define / { s///; s/ .*//; s/^/#pragma GCC poison /p; }' \
+    *-config-devices.h *-config-target.h | \
+    sort -u > config-poison.h
+
 # Save the configure command line for later reuse.
 cat <<EOD >config.status
 #!/bin/sh
diff --git a/include/exec/poison.h b/include/exec/poison.h
index 3250fc1d52..ae2f9d1e70 100644
--- a/include/exec/poison.h
+++ b/include/exec/poison.h
@@ -4,6 +4,8 @@
 #ifndef HW_POISON_H
 #define HW_POISON_H
 
+#include "config-poison.h"
+
 #pragma GCC poison TARGET_I386
 #pragma GCC poison TARGET_X86_64
 #pragma GCC poison TARGET_AARCH64
-- 
2.27.0

+Richard/Claudio

On 4/14/21 1:20 PM, 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 many of the
> macros in include/exec/poison.h - but it's cumbersome to maintain this
> list manually. Thus let's generate an additional list of poisoned macros
> automatically from the current config switches - this should give us a
> much better test coverage via the different CI configurations.
> 
> 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.

I know if we poison CONFIG_TCG, almost nothing build, but I fail to
see how it is different from the other accelerators. I suppose in the
future (maybe with Claudio's effort) we could have it not special.

> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  Makefile              | 2 +-
>  configure             | 5 +++++
>  include/exec/poison.h | 2 ++
>  3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index bcbbec71a1..4cab10a2a4 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -213,7 +213,7 @@ qemu-%.tar.bz2:
>  
>  distclean: clean
>  	-$(quiet-@)test -f build.ninja && $(NINJA) $(NINJAFLAGS) -t clean -g || :
> -	rm -f config-host.mak config-host.h*
> +	rm -f config-host.mak config-host.h* config-poison.h
>  	rm -f tests/tcg/config-*.mak
>  	rm -f config-all-disas.mak config.status
>  	rm -f roms/seabios/config.mak roms/vgabios/config.mak
> diff --git a/configure b/configure
> index 4f374b4889..a0f0601e7e 100755
> --- a/configure
> +++ b/configure
> @@ -6440,6 +6440,11 @@ if test -n "${deprecated_features}"; then
>      echo "  features: ${deprecated_features}"
>  fi
>  

Maybe a one line comment (but since it is obvious, I don't mind):

   # Filter out CONFIG_TCG and CONFIG_USER_ONLY which are special

> +sed -n -e '/CONFIG_TCG/d' -e '/CONFIG_USER_ONLY/d' \
> +    -e '/^#define / { s///; s/ .*//; s/^/#pragma GCC poison /p; }' \
> +    *-config-devices.h *-config-target.h | \
> +    sort -u > config-poison.h
> +

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

On 15/04/2021 10.34, Philippe Mathieu-Daudé wrote:
> +Richard/Claudio
> 
> On 4/14/21 1:20 PM, 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 many of the
>> macros in include/exec/poison.h - but it's cumbersome to maintain this
>> list manually. Thus let's generate an additional list of poisoned macros
>> automatically from the current config switches - this should give us a
>> much better test coverage via the different CI configurations.
>>
>> 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.
> 
> I know if we poison CONFIG_TCG, almost nothing build, but I fail to
> see how it is different from the other accelerators. 

You could argue that TCG is not specific to a target, i.e. it is either 
available for all targets, or it is disabled for all targets, so this is 
rather like a host config option than a target specific option.

>> diff --git a/configure b/configure
>> index 4f374b4889..a0f0601e7e 100755
>> --- a/configure
>> +++ b/configure
>> @@ -6440,6 +6440,11 @@ if test -n "${deprecated_features}"; then
>>       echo "  features: ${deprecated_features}"
>>   fi
>>   
> 
> Maybe a one line comment (but since it is obvious, I don't mind):
> 
>     # Filter out CONFIG_TCG and CONFIG_USER_ONLY which are special

Ok, makes sense, I can add that.

>> +sed -n -e '/CONFIG_TCG/d' -e '/CONFIG_USER_ONLY/d' \
>> +    -e '/^#define / { s///; s/ .*//; s/^/#pragma GCC poison /p; }' \
>> +    *-config-devices.h *-config-target.h | \
>> +    sort -u > config-poison.h
>> +
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Thanks!

   Thomas