Re: [PATCH] Only compile the hypervisor with -Wdeclaration-after-statement

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Tue, Dec 5, 2023 at 4:49 PM Julien Grall <julien@xxxxxxx> wrote:
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Right now, all tools and hypervisor will be complied with the option
> -Wdeclaration-after-statement. While most of the code in the hypervisor
> is controlled by us, for tools we may import external libraries.
>
> The build will fail if one of them are using the construct we are
> trying to prevent. This is the case when building against Python 3.12
> and Yocto:
>
> | In file included from 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/Python.h:44,
> |                  from xen/lowlevel/xc/xc.c:8:
> | 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/object.h:
>  In function 'Py_SIZE':
> | 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/object.h:233:5:
>  error: ISO C90 forbids mixed declarations and code 
> [-Werror=declaration-after-statement]
> |   233 |     PyVarObject *var_ob = _PyVarObject_CAST(ob);
> |       |     ^~~~~~~~~~~
> | In file included from 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/Python.h:53:
> | 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/cpython/longintrepr.h:
>  In function '_PyLong_CompactValue':
> | 
> /srv/storage/alex/yocto/build-virt/tmp/work/core2-64-poky-linux/xen-tools/4.17+stable/recipe-sysroot/usr/include/python3.12/cpython/longintrepr.h:121:5:
>  error: ISO C90 forbids mixed declarations and code 
> [-Werror=declaration-after-statement]
> |   121 |     Py_ssize_t sign = 1 - (op->long_value.lv_tag & 
> _PyLong_SIGN_MASK);
> |       |     ^~~~~~~~~~
> | cc1: all warnings being treated as errors
>
> Looking at the tools directory, a fair few directory already add
> -Wno-declaration-after-statement to inhibit the default behavior.
>
> We have always build the hypervisor with the flag, so for now remove
> only the flag for anything but the hypervisor. We can decide at later
> time whether we want to relax.
>
> Also remove the -Wno-declaration-after-statement in some subdirectory
> as the flag is now unnecessary.
>
> Part of the commit message was take from Alexander's first proposal:
>
> Link: 
> https://lore.kernel.org/xen-devel/20231128174729.3880113-1-alex@xxxxxxxxxxxxx/
> Reported-by: Alexander Kanavin <alex@xxxxxxxxxxxxx>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Tested-by: Jason Andryuk <jandryuk@xxxxxxxxx>

Also needed for compiling on Fedora 39.

Thanks,
Jason