Re: [PATCH v3 02/10] libvhost-user: Replace typeof with __typeof__

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/21/22 14:10, Marcel Holtmann wrote:
> Strictly speaking only -std=gnu99 support the usage of typeof and for
> easier inclusion in external projects, it is better to use __typeof__.
> 
>    CC       libvhost-user.o
> libvhost-user.c: In function ‘vu_log_queue_fill’:
> libvhost-user.c:86:13: error: implicit declaration of function ‘typeof’ [-Werror=implicit-function-declaration]
>     86 |             typeof(x) _min1 = (x);              \
>        |             ^~~~~~
> 
> Changing these two users of typeof makes the compiler happy and no extra
> flags or pragmas need to be provided.
> 
> Signed-off-by: Marcel Holtmann<marcel@holtmann.org>
> Reviewed-by: Philippe Mathieu-Daudé<philmd@linaro.org>

The build system uses "c_std=gnu99".  If you are extracting 
libvhost-user and not using its build files, you need to add --std=gnu99 
yourself when compiling.

If you really don't want to do that, as long as it's just a couple 
underscores that's fine I guess, but mixed declarations and code are 
going to reappear sooner or later.  Please add a patch like this:

diff --git a/subprojects/libvhost-user/meson.build 
b/subprojects/libvhost-user/meson.build
index 39825d9404ae..5deecbfe377d 100644
--- a/subprojects/libvhost-user/meson.build
+++ b/subprojects/libvhost-user/meson.build
@@ -1,6 +1,13 @@
  project('libvhost-user', 'c',
          license: 'GPL-2.0-or-later',
-        default_options: ['c_std=gnu99'])
+        default_options: ['warning_level=1', 'c_std=gnu99'])
+
+cc = meson.get_compiler('c')
+add_project_arguments(cc.get_supported_arguments(
+  '-Wsign-compare',
+  '-Wdeclaration-after-statement',
+  '-Wstrict-aliasing'),
+  native: false, language: 'c')

  threads = dependency('threads')
  glib = dependency('glib-2.0')


to avoid regressions, and likewise for libvduse.

Paolo