[libvirt PATCH] meson: avoid bogus warnings from clang and g_autoptr
Clang has previously had trouble with G_DEFINE_AUTOPTR_CLEANUP_FUNC generated code, thinking it was unused. We turn off -Wunused-function to avoid tripping up on that with CLang. New CLang has started having trouble with g_autoptr now too. In usage scenarios where the variable is set, but never again read, it thinks it is unused not realizing the destructor has useful side effects. For this we have to skip -Wunused-but-set-variable on CLang. Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- meson.build | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/meson.build b/meson.build index 5af09d319a..dbd70b6483 100644 --- a/meson.build +++ b/meson.build @@ -470,6 +470,26 @@ if get_option('warning_level') == '2' supported_cc_flags += [ '-Wno-unused-function' ] endif + # Clang complains about unused variables in many scenarios arelated + # to attribute((cleanup)) aka g_auto* + w_unused_but_set_var_args = [ '-Wunused-but-set-variable', '-Werror' ] + w_unused_but_set_var_code = ''' + static inline void free_pointer (void *p) { + void **pp = (void**)p; + free (*pp); + } + + int main(void) { + __attribute__((cleanup(free_pointer))) char *buffer = 0x0; + buffer = 0x1; + } + ''' + # We previously turned on unused-but-set-variable, so we must turn + # it off again explicitly now. + if not cc.compiles(w_unused_but_set_var_code, args: w_unused_but_set_var_args) + supported_cc_flags += [ '-Wno-unused-but-set-variable' ] + endif + endif add_project_arguments(supported_cc_flags, language: 'c') -- 2.31.1
On Tue, Aug 31, 2021 at 03:08:19PM +0100, Daniel P. Berrangé wrote:
Clang has previously had trouble with G_DEFINE_AUTOPTR_CLEANUP_FUNC generated code, thinking it was unused. We turn off -Wunused-function to avoid tripping up on that with CLang.
New CLang has started having trouble with g_autoptr now too. In usage scenarios where the variable is set, but never again read, it thinks it is unused not realizing the destructor has useful side effects. For this we have to skip -Wunused-but-set-variable on CLang.
s/CLang/Clang/
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- meson.build | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/meson.build b/meson.build index 5af09d319a..dbd70b6483 100644 --- a/meson.build +++ b/meson.build @@ -470,6 +470,26 @@ if get_option('warning_level') == '2' supported_cc_flags += [ '-Wno-unused-function' ] endif
+ # Clang complains about unused variables in many scenarios arelated
s/arelated/related/
+ # to attribute((cleanup)) aka g_auto* + w_unused_but_set_var_args = [ '-Wunused-but-set-variable', '-Werror' ] + w_unused_but_set_var_code = ''' + static inline void free_pointer (void *p) { + void **pp = (void**)p; + free (*pp); + } + + int main(void) { + __attribute__((cleanup(free_pointer))) char *buffer = 0x0; + buffer = 0x1; + } + ''' + # We previously turned on unused-but-set-variable, so we must turn + # it off again explicitly now. + if not cc.compiles(w_unused_but_set_var_code, args: w_unused_but_set_var_args) + supported_cc_flags += [ '-Wno-unused-but-set-variable' ] + endif + endif add_project_arguments(supported_cc_flags, language: 'c')
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
On Tue, Aug 31, 2021 at 05:23:08PM +0200, Pavel Hrdina wrote:
On Tue, Aug 31, 2021 at 03:08:19PM +0100, Daniel P. Berrangé wrote:
Clang has previously had trouble with G_DEFINE_AUTOPTR_CLEANUP_FUNC generated code, thinking it was unused. We turn off -Wunused-function to avoid tripping up on that with CLang.
New CLang has started having trouble with g_autoptr now too. In usage scenarios where the variable is set, but never again read, it thinks it is unused not realizing the destructor has useful side effects. For this we have to skip -Wunused-but-set-variable on CLang.
s/CLang/Clang/
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- meson.build | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/meson.build b/meson.build index 5af09d319a..dbd70b6483 100644 --- a/meson.build +++ b/meson.build @@ -470,6 +470,26 @@ if get_option('warning_level') == '2' supported_cc_flags += [ '-Wno-unused-function' ] endif
+ # Clang complains about unused variables in many scenarios arelated
s/arelated/related/
+ # to attribute((cleanup)) aka g_auto* + w_unused_but_set_var_args = [ '-Wunused-but-set-variable', '-Werror' ] + w_unused_but_set_var_code = ''' + static inline void free_pointer (void *p) { + void **pp = (void**)p; + free (*pp); + } + + int main(void) { + __attribute__((cleanup(free_pointer))) char *buffer = 0x0; + buffer = 0x1; + } + ''' + # We previously turned on unused-but-set-variable, so we must turn + # it off again explicitly now. + if not cc.compiles(w_unused_but_set_var_code, args: w_unused_but_set_var_args) + supported_cc_flags += [ '-Wno-unused-but-set-variable' ] + endif + endif add_project_arguments(supported_cc_flags, language: 'c')
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Turns out this broke on macOS / FreeBSD with older CLang so will need a v2. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
participants (2)
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Daniel P. Berrangé -
Pavel Hrdina