| Message ID | 20180504160026.14017-4-berrange@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Document intent for supported build platforms and bump min glib to 2.42 | expand |
On 04/05/2018 18:00, Daniel P. Berrangé wrote: > There are two useful macros that can be defined before including > glib.h that are related to the min required glib version > > - GLIB_VERSION_MIN_REQUIRED > > When this is defined, if code uses an API that was deprecated > in this version, or older, a compiler warning will be emitted. > This alerts maintainers to update their code to whatever new > replacement API is now recommended best practice. > > - GLIB_VERSION_MAX_ALLOWED > > When this is defined, if code uses an API that was introduced > in a version that is newer than the declared version, a compiler > warning will be emitted. This alerts maintainers if new code > accidentally uses functionality that won't be available on some > supported platforms. > > The GLIB_VERSION_MAX_ALLOWED constant makes it a bit harder to opt > in to using specific new APIs with a GLIB_CHECK_VERSION conditional. > To workaround this Pragmas can be used to temporarily turn off the > -Wdeprecated-declarations compiler warning, while a static inline > compat function is implemented. Nothing needs that at this time, > so just illustrate it in a comment for benefit of future changes. Unfortunately there is one need, and it's a bug in glib itself: In file included from /usr/lib64/glib-2.0/include/glibconfig.h:9:0, from /usr/include/glib-2.0/glib/gtypes.h:32, from /usr/include/glib-2.0/glib/galloca.h:32, from /usr/include/glib-2.0/glib.h:30, from /home/pbonzini/work/upstream/qemu/include/glib-compat.h:29, from /home/pbonzini/work/upstream/qemu/include/qemu/osdep.h:107, from /home/pbonzini/work/upstream/qemu/disas/arm-a64.cc:21: /usr/include/glib-2.0/glib/glib-autocleanups.h: In function ‘void glib_autoptr_cleanup_GOptionGroup(GOptionGroup**)’: /usr/include/glib-2.0/glib/glib-autocleanups.h:63:45: error: ‘void g_option_group_unref(GOptionGroup*)’ is deprecated (declared at /usr/include/glib-2.0/glib/goption.h:372): Not available before 2.44 [-Werror=deprecated-declarations] G_DEFINE_AUTOPTR_CLEANUP_FUNC(GOptionGroup, g_option_group_unref) ^ /usr/include/glib-2.0/glib/gmacros.h:444:88: note: in definition of macro ‘G_DEFINE_AUTOPTR_CLEANUP_FUNC’ static inline void _GLIB_AUTOPTR_FUNC_NAME(TypeName) (TypeName **_ptr) { if (*_ptr) (func) (*_ptr); } \ ^ /usr/include/glib-2.0/glib/gmacros.h:444:100: error: ‘void g_option_group_unref(GOptionGroup*)’ is deprecated (declared at /usr/include/glib-2.0/glib/goption.h:372): Not available before 2.44 [-Werror=deprecated-declarations] static inline void _GLIB_AUTOPTR_FUNC_NAME(TypeName) (TypeName **_ptr) { if (*_ptr) (func) (*_ptr); } \ ^ /usr/include/glib-2.0/glib/glib-autocleanups.h:63:1: note: in expansion of macro ‘G_DEFINE_AUTOPTR_CLEANUP_FUNC’ G_DEFINE_AUTOPTR_CLEANUP_FUNC(GOptionGroup, g_option_group_unref) (This is RHEL7 glib2-2.50.3-3.el7.x86_64). Luckily you suggested the solution yourself---this seems to work: diff --git a/include/glib-compat.h b/include/glib-compat.h index d066f6d..ef07489 100644 --- a/include/glib-compat.h +++ b/include/glib-compat.h @@ -26,6 +26,8 @@ */ #define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_42 +_Pragma("GCC diagnostic push") +_Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") #include <glib.h> /* @@ -42,8 +44,6 @@ * signature that does what we need, but with a "_qemu" * suffix eg * - * _Pragma("GCC diagnostic push") - * _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") * static inline void g_foo_qemu(const char *wibble) * { * #if GLIB_CHECK_VERSION(X, Y, 0) @@ -52,12 +52,10 @@ * g_something_equivalent_in_older_glib(wibble); * #endif * } - * _Pragma("GCC diagnostic pop") * - * The Pragma calls turn off -Wdeprecated-declarations, - * ensuring this wrapper function impl doesn't trigger the - * compiler warning about using too new glib APIs. Finally - * we can do + * The _Pragma at the top of this file turns off -Wdeprecated-declarations, + * ensuring this wrapper function impl doesn't trigger the compiler warning + * about using too new glib APIs. Finally we can do * * #define g_foo(a) g_foo_qemu(a) * @@ -94,4 +92,6 @@ gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout); } while (0) #endif +_Pragma("GCC diagnostic pop") + #endif I'll give it a shot on clang too. Paolo
On Tue, May 08, 2018 at 05:17:40PM +0200, Paolo Bonzini wrote: > On 04/05/2018 18:00, Daniel P. Berrangé wrote: > > There are two useful macros that can be defined before including > > glib.h that are related to the min required glib version > > > > - GLIB_VERSION_MIN_REQUIRED > > > > When this is defined, if code uses an API that was deprecated > > in this version, or older, a compiler warning will be emitted. > > This alerts maintainers to update their code to whatever new > > replacement API is now recommended best practice. > > > > - GLIB_VERSION_MAX_ALLOWED > > > > When this is defined, if code uses an API that was introduced > > in a version that is newer than the declared version, a compiler > > warning will be emitted. This alerts maintainers if new code > > accidentally uses functionality that won't be available on some > > supported platforms. > > > > The GLIB_VERSION_MAX_ALLOWED constant makes it a bit harder to opt > > in to using specific new APIs with a GLIB_CHECK_VERSION conditional. > > To workaround this Pragmas can be used to temporarily turn off the > > -Wdeprecated-declarations compiler warning, while a static inline > > compat function is implemented. Nothing needs that at this time, > > so just illustrate it in a comment for benefit of future changes. > > Unfortunately there is one need, and it's a bug in glib itself: > > In file included from /usr/lib64/glib-2.0/include/glibconfig.h:9:0, > from /usr/include/glib-2.0/glib/gtypes.h:32, > from /usr/include/glib-2.0/glib/galloca.h:32, > from /usr/include/glib-2.0/glib.h:30, > from /home/pbonzini/work/upstream/qemu/include/glib-compat.h:29, > from /home/pbonzini/work/upstream/qemu/include/qemu/osdep.h:107, > from /home/pbonzini/work/upstream/qemu/disas/arm-a64.cc:21: > /usr/include/glib-2.0/glib/glib-autocleanups.h: In function ‘void glib_autoptr_cleanup_GOptionGroup(GOptionGroup**)’: > /usr/include/glib-2.0/glib/glib-autocleanups.h:63:45: error: ‘void g_option_group_unref(GOptionGroup*)’ is deprecated (declared at /usr/include/glib-2.0/glib/goption.h:372): Not available before 2.44 [-Werror=deprecated-declarations] > G_DEFINE_AUTOPTR_CLEANUP_FUNC(GOptionGroup, g_option_group_unref) > ^ > /usr/include/glib-2.0/glib/gmacros.h:444:88: note: in definition of macro ‘G_DEFINE_AUTOPTR_CLEANUP_FUNC’ > static inline void _GLIB_AUTOPTR_FUNC_NAME(TypeName) (TypeName **_ptr) { if (*_ptr) (func) (*_ptr); } \ > ^ > /usr/include/glib-2.0/glib/gmacros.h:444:100: error: ‘void g_option_group_unref(GOptionGroup*)’ is deprecated (declared at /usr/include/glib-2.0/glib/goption.h:372): Not available before 2.44 [-Werror=deprecated-declarations] > static inline void _GLIB_AUTOPTR_FUNC_NAME(TypeName) (TypeName **_ptr) { if (*_ptr) (func) (*_ptr); } \ > ^ > /usr/include/glib-2.0/glib/glib-autocleanups.h:63:1: note: in expansion of macro ‘G_DEFINE_AUTOPTR_CLEANUP_FUNC’ > G_DEFINE_AUTOPTR_CLEANUP_FUNC(GOptionGroup, g_option_group_unref) > > (This is RHEL7 glib2-2.50.3-3.el7.x86_64). > > Luckily you suggested the solution yourself---this seems to work: > > diff --git a/include/glib-compat.h b/include/glib-compat.h > index d066f6d..ef07489 100644 > --- a/include/glib-compat.h > +++ b/include/glib-compat.h > @@ -26,6 +26,8 @@ > */ > #define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_42 > > +_Pragma("GCC diagnostic push") > +_Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") > #include <glib.h> > > /* > @@ -42,8 +44,6 @@ > * signature that does what we need, but with a "_qemu" > * suffix eg > * > - * _Pragma("GCC diagnostic push") > - * _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") > * static inline void g_foo_qemu(const char *wibble) > * { > * #if GLIB_CHECK_VERSION(X, Y, 0) > @@ -52,12 +52,10 @@ > * g_something_equivalent_in_older_glib(wibble); > * #endif > * } > - * _Pragma("GCC diagnostic pop") > * > - * The Pragma calls turn off -Wdeprecated-declarations, > - * ensuring this wrapper function impl doesn't trigger the > - * compiler warning about using too new glib APIs. Finally > - * we can do > + * The _Pragma at the top of this file turns off -Wdeprecated-declarations, > + * ensuring this wrapper function impl doesn't trigger the compiler warning > + * about using too new glib APIs. Finally we can do > * > * #define g_foo(a) g_foo_qemu(a) > * > @@ -94,4 +92,6 @@ gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout); > } while (0) > #endif > > +_Pragma("GCC diagnostic pop") > + > #endif > > I'll give it a shot on clang too. Ok, that change looks fine with me assuming it passes your build tests. In fact that is what I had done in an earlier version. Regards, Daniel
On 08/05/2018 17:19, Daniel P. Berrangé wrote: > Ok, that change looks fine with me assuming it passes your build tests. > In fact that is what I had done in an earlier version. > > Regards, > Daniel Actually there is a use of g_strv_contains in tests/test-qga.c. It is guarded by GLIB_CHECK_VERSION(2, 44, 0) but the right fix should be to include the compatibility function instead. For now I am dropping this patch. Paolo
On Tue, May 08, 2018 at 06:02:55PM +0200, Paolo Bonzini wrote: > On 08/05/2018 17:19, Daniel P. Berrangé wrote: > > Ok, that change looks fine with me assuming it passes your build tests. > > In fact that is what I had done in an earlier version. > > > > Regards, > > Daniel > > Actually there is a use of g_strv_contains in tests/test-qga.c. It is > guarded by GLIB_CHECK_VERSION(2, 44, 0) but the right fix should be to > include the compatibility function instead. > > For now I am dropping this patch. Ok, I'll have a look at that, and re-post an updated patch later. There are a few other uses of GLIB_CHECK_VERSION to be investigated too I see. Regards, Daniel
diff --git a/include/glib-compat.h b/include/glib-compat.h index 3b340ab33c..d066f6d257 100644 --- a/include/glib-compat.h +++ b/include/glib-compat.h @@ -16,8 +16,57 @@ #ifndef QEMU_GLIB_COMPAT_H #define QEMU_GLIB_COMPAT_H +/* Ask for warnings for anything that was marked deprecated in + * the defined version, or before. It is a candidate for rewrite. + */ +#define GLIB_VERSION_MIN_REQUIRED GLIB_VERSION_2_42 + +/* Ask for warnings if code tries to use function that did not + * exist in the defined version. These risk breaking builds + */ +#define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_42 + #include <glib.h> +/* + * Note that because of the GLIB_VERSION_MAX_ALLOWED constant + * above, allowing use of functions from newer GLib via this + * compat header needs a little trickery to prevent warnings + * being emitted. + * + * Consider a function from newer glib-X.Y that we want to use + * + * int g_foo(const char *wibble) + * + * We must define a static inline function with the same + * signature that does what we need, but with a "_qemu" + * suffix eg + * + * _Pragma("GCC diagnostic push") + * _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") + * static inline void g_foo_qemu(const char *wibble) + * { + * #if GLIB_CHECK_VERSION(X, Y, 0) + * g_foo(wibble) + * #else + * g_something_equivalent_in_older_glib(wibble); + * #endif + * } + * _Pragma("GCC diagnostic pop") + * + * The Pragma calls turn off -Wdeprecated-declarations, + * ensuring this wrapper function impl doesn't trigger the + * compiler warning about using too new glib APIs. Finally + * we can do + * + * #define g_foo(a) g_foo_qemu(a) + * + * So now the code elsewhere in QEMU, which *does* have the + * -Wdeprecated-declarations warning active, can call + * g_foo(...) as normal, without generating warnings. + */ + + #if defined(_WIN32) && !GLIB_CHECK_VERSION(2, 50, 0) /* * g_poll has a problem on Windows when using
There are two useful macros that can be defined before including glib.h that are related to the min required glib version - GLIB_VERSION_MIN_REQUIRED When this is defined, if code uses an API that was deprecated in this version, or older, a compiler warning will be emitted. This alerts maintainers to update their code to whatever new replacement API is now recommended best practice. - GLIB_VERSION_MAX_ALLOWED When this is defined, if code uses an API that was introduced in a version that is newer than the declared version, a compiler warning will be emitted. This alerts maintainers if new code accidentally uses functionality that won't be available on some supported platforms. The GLIB_VERSION_MAX_ALLOWED constant makes it a bit harder to opt in to using specific new APIs with a GLIB_CHECK_VERSION conditional. To workaround this Pragmas can be used to temporarily turn off the -Wdeprecated-declarations compiler warning, while a static inline compat function is implemented. Nothing needs that at this time, so just illustrate it in a comment for benefit of future changes. Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- include/glib-compat.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+)