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    SubjectRe: [PATCH 5/5 ver3] debug: BUILD_BUG_ON: error on non-const expressions

    Fix BUILD_BUG_ON to not silently drop non-compile-time
    visible expressions. It will now produce a compilation
    error if so.

    The code to BUILD_BUG_ON_ZERO was done by:
    Jan Beulich <jbeulich@novell.com>

    The code to BUILD_BUG_ON is a small variation to Jan's
    code inspired by Rusty Russell. Which gives me better
    compilations semantics, and makes BUILD_BUG_ON behave
    more like BUG_ON.

    Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
    TO: Jan Beulich <jbeulich@novell.com>
    CC: Ingo Molnar <mingo@elte.hu>
    CC: Rusty Russell <rusty@rustcorp.com.au>
    CC: Alexey Dobriyan <adobriyan@gmail.com>
    CC: Andrew Morton <akpm@linux-foundation.org>
    CC: Theodore Tso <tytso@mit.edu>
    CC: David S. Miller <davem@davemloft.net>
    ---
    include/linux/compiler.h | 11 ++++++-----
    1 files changed, 6 insertions(+), 5 deletions(-)

    diff --git a/include/linux/compiler.h b/include/linux/compiler.h
    index 90fa975..f882410 100644
    --- a/include/linux/compiler.h
    +++ b/include/linux/compiler.h
    @@ -194,14 +194,15 @@ extern void __chk_io_ptr(const volatile void __iomem *);
    */
    #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

    -/* Force a compilation error if condition is true */
    -#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
    -
    /* Force a compilation error if condition is true, but also produce a
    result (of value 0 and type size_t), so the expression can be used
    - e.g. in a structure initializer (or where-ever else comma expressions
    + e.g. in a structure initializer (or where-ever full statements
    aren't permitted). */
    -#define BUILD_BUG_ON_ZERO(e) (sizeof(char[1 - 2 * !!(e)]) - 1)
    +#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int: -!!(e); }))
    +
    +/* Force a compilation error if condition is true */
    +#define BUILD_BUG_ON(e) \
    + do { struct {int: -!!(e); } x __maybe_unused; } while (0)

    /* Trap pasters of __FUNCTION__ at compile-time */
    #define __FUNCTION__ (__func__)
    --
    1.5.6.rc1.5.gadf6



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