Daniel Santos [Thu, 7 Feb 2013 01:25:47 +0000 (12:25 +1100)]
compiler.h, bug.h: Prevent double error messages with BUILD_BUG{,_ON}
Prior to the introduction of __attribute__((error("msg"))) in gcc 4.3,
creating compile-time errors required a little trickery. BUILD_BUG{,_ON}
uses this attribute when available to generate compile-time errors, but
also uses the negative-sized array trick for older compilers, resulting in
two error messages in some cases. The reason it's "some" cases is that as
of gcc 4.4, the negative-sized array will not create an error in some
situations, like inline functions.
This patch replaces the negative-sized array code with the new
__compiletime_error_fallback() macro which expands to the same thing
unless the the error attribute is available, in which case it expands to
do{}while(0), resulting in exactly one compile-time error on all versions
of gcc.
Note that we are not changing the negative-sized array code for the
unoptimized version of BUILD_BUG_ON, since it has the potential to catch
problems that would be disabled in later versions of gcc were
__compiletime_error_fallback used. The reason is that that an unoptimized
build can't always remove calls to an error-attributed function call (like
we are using) that should effectively become dead code if it were
optimized. However, using a negative-sized array with a similar value
will not result in an false-positive (error). The only caveat being that
it will also fail to catch valid conditions, which we should be expecting
in an unoptimized build anyway.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Daniel Santos [Thu, 7 Feb 2013 01:25:46 +0000 (12:25 +1100)]
bug.h: Make BUILD_BUG_ON generate compile-time error
Negative sized arrays wont create a compile-time error in some cases
starting with gcc 4.4 (e.g., inlined functions), but gcc 4.3 introduced
the error function attribute that will. This patch modifies BUILD_BUG_ON
to behave like BUILD_BUG already does, using the error function attribute
so that you don't have to build the entire kernel to discover that you
have a problem, and then enjoy trying to track it down from a link-time
error.
Also, we are only including asm/bug.h and then expecting that
linux/compiler.h will eventually be included to define __linktime_error
(used in BUILD_BUG_ON). This patch includes it directly for clarity and
to avoid the possibility of changes in <arch>/*/include/asm/bug.h being
changed or not including linux/compiler.h for some reason.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Daniel Santos [Thu, 7 Feb 2013 01:25:46 +0000 (12:25 +1100)]
bug.h: Prevent double evaulation of in BUILD_BUG_ON
When calling BUILD_BUG_ON in an optimized build using gcc 4.3 and later,
the condition will be evaulated twice, possibily with side-effects. This
patch eliminates that error.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Daniel Santos [Thu, 7 Feb 2013 01:25:45 +0000 (12:25 +1100)]
bug.h: Fix BUILD_BUG_ON macro in __CHECKER__
When __CHECKER__ is defined, we disable all of the BUILD_BUG.* macros.
However, both BUILD_BUG_ON_NOT_POWER_OF_2 and BUILD_BUG_ON was evaluating
to nothing in this case, and we want (0) since this is a function-like
macro that will be followed by a semicolon.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
__linktime_error() does the same thing as __compiletime_error() and is
only used in bug.h. Since the macro defines a function attribute that
will cause a failure at compile-time (not link-time), it makes more sense
to keep __compiletime_error(), which is also neatly mated with
__compiletime_warning().
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Daniel Santos [Thu, 7 Feb 2013 01:25:45 +0000 (12:25 +1100)]
compiler-gcc{3,4}.h: Use GCC_VERSION macro
Using GCC_VERSION reduces complexity, is easier to read and is GCC's
recommended mechanism for doing version checks. (Just don't ask me why
they didn't define it in the first place.) This also makes it easy to
merge compiler-gcc{,3,4}.h should somebody want to.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Throughout compiler*.h, many version checks are made. These can be
simplified by using the macro that gcc's documentation recommends.
However, my primary reason for adding this is that I need bug-check macros
that are enabled at certain gcc versions and it's cleaner to use this
macro than the tradition method:
Daniel Santos [Thu, 7 Feb 2013 01:25:44 +0000 (12:25 +1100)]
compiler-gcc4.h: Reorder macros based upon gcc ver
This helps to keep the file from getting confusing, removes one duplicate
version check and should encourage future editors to put new macros where
they belong.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
projects / karo-tx-linux.git / log