[libvirt] [PATCH] Do not inline virNumaNodeIsAvailable

[Daniel P. Berrange]

On Mon, Mar 09, 2015 at 11:01:31AM +0100, Martin Kletzander wrote:
> On Thu, Mar 05, 2015 at 11:09:41AM +0000, Daniel P. Berrange wrote:
> >On Thu, Mar 05, 2015 at 12:05:52PM +0100, Ján Tomko wrote:
> >>Explicitly request that virNumaNodeIsAvailable not be inlined.
> >>This fixes the test suite when building with clang (3.5.1).
> >
> >Huh, so clang will inline functions, even if they are exported
> >in the .so library ?  Is there some clang compiler flag we can
> >use to stop that ?  I'd only expect it to inline stuff which
> >was declared static, or whose impl body was in the header file
> >
> 
> If I understand it correctly, that means that clang is not
> "compatible" with gcc.
> 
> Excerpt from gcc online docs [1]:
> 
>  When a function is both inline and static, if all calls to the
>  function are integrated into the caller, and the function's address
>  is never used, then the function's own assembler code is never
>  referenced.
> 
> Excerpt from gcc online docs [1]:
> 
>  By default, Clang builds C code in GNU C11 mode, so it uses standard
>  C99 semantics for the inline keyword. These semantics are different
>  from those in GNU C89 mode, which is the default mode in versions of
>  GCC prior to 5.0.
> 
> However further reading of the second documentation and c89 semantics
> it doesn't say anything about the fact that such function should be
> inlined.

But we haven't added the 'inline' keyword to this function at
all - it is just a normal function marked for export in the
.so file, so I'm puzzelled why it is getting inlined.

> 
> Anyway, is this clang 3.6 specific?  I don't have this problem when
> compiling with 3.5.  Nor does this show with gcc -std=gnu11.  I'm
> getting 3.6 to check whether that's the difference.
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc/Inline.html
> [2] http://clang.llvm.org/compatibility.html
> 
> >>---
> >>This only leaves the mysterious check-protocol failure.
> 
> That's not that mysterious, it's just that we check the order and
> clang sorts enums before structs, but gcc doesn't.  Also clang adds
> "public:" to structs, so it probably treats it as a C++ or C# structs
> or something?
> 
> >>And too large stack frame size when building the tests with -O0.
> >>
> 
> I'm using CFLAGS='-O0 -ggdb -Wno-frame-larger-than=' for this as a
> parameter for autogen.sh O:-)
> 
> >> src/internal.h     | 10 ++++++++++
> >> src/util/virnuma.h |  3 ++-
> >> 2 files changed, 12 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/src/internal.h b/src/internal.h
> >>index 4d473af..84aa330 100644
> >>--- a/src/internal.h
> >>+++ b/src/internal.h
> >>@@ -139,6 +139,16 @@
> >> #  endif
> >>
> >> /**
> >>+ * ATTRIBUTE_NOINLINE:
> >>+ *
> >>+ * Macro to indicate a function that cannot be inlined
> >>+ * (e.g. a function that is mocked in the test suite)
> >>+ */
> >>+#  ifndef ATTRIBUTE_NOINLINE
> >>+#   define ATTRIBUTE_NOINLINE __attribute__((__noinline__))
> >>+#  endif
> >>+
> >>+/**
> >>  * ATTRIBUTE_SENTINEL:
> >>  *
> >>  * Macro to check for NULL-terminated varargs lists
> >>diff --git a/src/util/virnuma.h b/src/util/virnuma.h
> >>index 1f3c0ad..4ddcc5a 100644
> >>--- a/src/util/virnuma.h
> >>+++ b/src/util/virnuma.h
> >>@@ -37,7 +37,8 @@ virBitmapPtr virNumaGetHostNodeset(void);
> >> bool virNumaNodesetIsAvailable(virBitmapPtr nodeset);
> >> bool virNumaIsAvailable(void);
> >> int virNumaGetMaxNode(void);
> >>-bool virNumaNodeIsAvailable(int node);
> >>+bool virNumaNodeIsAvailable(int node)
> >>+    ATTRIBUTE_NOINLINE;
> >> int virNumaGetDistances(int node,
> >>                         int **distances,
> >>                         int *ndistances);
> >
> >Regards,
> >Daniel
> >--
> >|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
> >|: http://libvirt.org              -o-             http://virt-manager.org :|
> >|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
> >|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|
> >
> >--
> >libvir-list mailing list
> >libvir-list at redhat.com
> >https://www.redhat.com/mailman/listinfo/libvir-list



Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|