Re: [PATCH 19/41] compiler.h: replace QEMU_NORETURN with G_NORETURN

[Stefan Weil via <qemu-devel@nongnu.org>]

Please excuse the late report, but this old patch causes a build failure 
for me:

Am 20.04.22 um 15:26 schrieb marcandre.lureau@redhat.com:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> G_NORETURN was introduced in glib 2.68, fallback to G_GNUC_NORETURN in
> glib-compat.
> 
> Note that this attribute must be placed before the function declaration
> (bringing a bit of consistency in qemu codebase usage).
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
[...]
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 848916f5165c..14b6b65a5fa9 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -177,7 +177,8 @@ extern "C" {
>    * supports QEMU_ERROR, this will be reported at compile time; otherwise
>    * this will be reported at link time due to the missing symbol.
>    */
> -extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
> +extern G_NORETURN
> +void QEMU_ERROR("code path is reachable")
>       qemu_build_not_reached_always(void);
>   #if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
>   #define qemu_build_not_reached()  qemu_build_not_reached_always()

The placement of G_NORETURN causes a compiler error for C++ code in 
cross builds for Windows (see below). C++ expects the attribute 
[[noreturn]] before the extern statement.

I updated my Debian build environment to Debian bookworm and a recent 
cross glib, so maybe the problem was hidden in previous builds because I 
used a rather old glib or an older g++ cross compiler.

Regards,
Stefan


In file included from /mingw64/lib/glib-2.0/include/glibconfig.h:9,
                  from /mingw64/include/glib-2.0/glib/gtypes.h:34,
                  from /mingw64/include/glib-2.0/glib/galloca.h:34,
                  from /mingw64/include/glib-2.0/glib.h:32,
                  from 
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/glib-compat.h:32,
                  from 
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/qemu/osdep.h:144,
                  from ../../../qga/vss-win32/requester.cpp:13:
/mingw64/include/glib-2.0/glib/gmacros.h:1076:21: error: standard 
attributes in middle of decl-specifiers
  1076 | # define G_NORETURN [[noreturn]]
       |                     ^
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/qemu/osdep.h:240:8: 
note: in expansion of macro ‘G_NORETURN’
   240 | extern G_NORETURN
       |        ^~~~~~~~~~
/mingw64/include/glib-2.0/glib/gmacros.h:1076:21: note: standard 
attributes must precede the decl-specifiers to apply to the declaration, 
or follow them to apply to the type
  1076 | # define G_NORETURN [[noreturn]]
       |                     ^
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/qemu/osdep.h:240:8: 
note: in expansion of macro ‘G_NORETURN’
   240 | extern G_NORETURN
       |        ^~~~~~~~~~
/mingw64/include/glib-2.0/glib/gmacros.h:1076:21: warning: attribute 
ignored [-Wattributes]
  1076 | # define G_NORETURN [[noreturn]]
       |                     ^
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/qemu/osdep.h:240:8: 
note: in expansion of macro ‘G_NORETURN’
   240 | extern G_NORETURN
       |        ^~~~~~~~~~
/mingw64/include/glib-2.0/glib/gmacros.h:1076:21: note: an attribute 
that appertains to a type-specifier is ignored
  1076 | # define G_NORETURN [[noreturn]]
       |                     ^
/home/stefan/src/qemu/repo.or.cz/qemu/ar7/include/qemu/osdep.h:240:8: 
note: in expansion of macro ‘G_NORETURN’
   240 | extern G_NORETURN
       |        ^~~~~~~~~~
../../../qga/vss-win32/requester.cpp: In function ‘HRESULT 
requester_init()’:
../../../qga/vss-win32/requester.cpp:72:34: warning: cast between 
incompatible function types from ‘FARPROC’ {aka ‘long long int (*)()’} 
to ‘t_CreateVssBackupComponents’ {aka ‘long int 
(*)(IVssBackupComponents**)’} [-Wcast-function-type]
    72 |     pCreateVssBackupComponents = (t_CreateVssBackupComponents)
       |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    73 |         GetProcAddress(hLib,
       |         ~~~~~~~~~~~~~~~~~~~~
    74 | #ifdef _WIN64 /* 64bit environment */
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    75 | 
"?CreateVssBackupComponents@@YAJPEAPEAVIVssBackupComponents@@@Z"
       | 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    76 | #else /* 32bit environment */
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    77 | 
"?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z"
       | 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    78 | #endif
       | ~~~~~~
    79 |         );
       |         ~
../../../qga/vss-win32/requester.cpp:85:34: warning: cast between 
incompatible function types from ‘FARPROC’ {aka ‘long long int (*)()’} 
to ‘t_VssFreeSnapshotProperties’ {aka ‘void (*)(VSS_SNAPSHOT_PROP*)’} 
[-Wcast-function-type]
    85 |     pVssFreeSnapshotProperties = (t_VssFreeSnapshotProperties)
       |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    86 |         GetProcAddress(hLib, "VssFreeSnapshotProperties");
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ninja: build stopped: subcommand failed.