Re: [patch 01/10] compiler: define __attribute_unused__

David Rientjes
2007-05-02T06:42:18Z

On Wed, 2 May 2007, Rusty Russell wrote:

> OTOH, your point about "__unneeded" is well taken. "__needed" and
> "__optional" perhaps? But their feature is *exactly* that the don't
> look like the gcc attributes, hence avoid their semantic screwage.
>

Hmm, __optional doesn't sound appropriate either. Since this is going to
be defined to be __attribute__ ((unused)), it can apply to both functions
and variables. It should be applied to a function if it truly is
unreferenced within the tree (and there are several examples of this
current HEAD) and we don't want to use __needed because it still emits the
function code even though it suppresses the warning. So saying a function
that has no callers is "__optional" makes no sense since its code isn't
going to be emitted in gcc >=3.4.

What's your opinion of my __needed and __maybe_unused idea such as the
following?

compiler: define __maybe_unused

Define __maybe_unused to apply to both functions or variables as
__attribute__((unused)). This will not emit a compile-time warning when
a function or variable is declared but unreferenced.

We eventually want to change the name of __attribute_used__ to __used.

Signed-off-by: David Rientjes <rientjes@google.com>
---
include/linux/compiler-gcc.h | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -37,3 +37,4 @@
#define noinline __attribute__((noinline))
#define __attribute_pure__ __attribute__((pure))
#define __attribute_const__ __attribute__((__const__))
+#define __maybe_unused __attribute__((unused))