Messages in this thread | | | Date | Mon, 14 Sep 2009 19:12:45 -0400 | Subject | Re: [PATCH 11/11] Use unreachable() in asm-generic/bug.h for !CONFIG_BUG case. | From | Brian Gerst <> |
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On Mon, Sep 14, 2009 at 5:55 PM, David Daney <ddaney@caviumnetworks.com> wrote: > The subject says it all (most). The only drawback here is that for a > pre-GCC-5.4 compiler, instead of expanding to nothing we now expand > BUG() to an endless loop. Before the patch when configured with > !CONFIG_BUG() you might get some warnings, but the code would be > small. After the patch there are no warnings, but there is an endless > loop at each BUG() site. > > Of course for the GCC-4.5 case we get the best of both worlds. > > Signed-off-by: David Daney <ddaney@caviumnetworks.com> > Suggested-by: Ingo Molnar <mingo@elte.hu> > CC: Ingo Molnar <mingo@elte.hu> > --- > include/asm-generic/bug.h | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h > index 4b67559..e952242 100644 > --- a/include/asm-generic/bug.h > +++ b/include/asm-generic/bug.h > @@ -89,11 +89,11 @@ extern void warn_slowpath_null(const char *file, const int line); > > #else /* !CONFIG_BUG */ > #ifndef HAVE_ARCH_BUG > -#define BUG() do {} while(0) > +#define BUG() unreachable() > #endif > > #ifndef HAVE_ARCH_BUG_ON > -#define BUG_ON(condition) do { if (condition) ; } while(0) > +#define BUG_ON(condition) do { if (condition) unreachable(); } while (0) > #endif > > #ifndef HAVE_ARCH_WARN_ON > --
This seems wrong to me. Wouldn't you always want to do the endless loop? In the absence of an arch-specific method to jump to an exception handler, it isn't really unreachable. On gcc 4.5 this would essentially become a no-op.
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