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    SubjectRe: [PATCH v3 0/2] Stop some of the abuse of BUG() where compile time checks should be used.
    On 11/23/2011 03:57 PM, Linus Torvalds wrote:
    > Btw, would it possibly make sense to make the string more useful?
    >
    > For example using __FILE__ and __LINE__, or possibly letting the user
    > of the BUILD_BUG() give a string ("Using HMASK without
    > CONFIG_HUGEPAGE").

    We thought about doing that, but without doing some complex preprocessor
    fu, the GCC attribute ((error())) thing doesn't do what we want.

    It appears that if more than a single instance of the construct is used
    in a compilation unit, the string emitted by the compiler for any of the
    violations will be the last string encountered.

    So if you did something like:

    .
    .
    .
    Line 99: BUILD_BUG("You failed on line 99");
    .
    .
    .
    .
    Line 666: BUILD_BUG("You failed on line 666");
    .
    .
    .

    The message emitted for a failure at line 99 would be "You failed on
    line 666". Which is probably worse than no message at all.

    It may be possible to do something like:

    #define _LINENAME_CONCAT( _name_, _line_ ) _name_##_line_
    #define _LINENAME(_name_, _line_) _LINENAME_CONCAT(_name_,_line_)

    #define _BUILD_BUG(MSG,FUBAR) \
    do { \
    extern void FUBAR (void) \
    __linktime_error("BUILD_BUG failed: " MSG); \
    FUBAR (); \
    } while (0)

    #define BUILD_BUG(M,A) _BUILD_BUG(M, _LINENAME(__build_bug_failed,__LINE__))

    But it didn't seem worth it.

    >
    > Whatever. It's bikeshedding - what would probably be more important
    > would be to get this into linux-next so that we find out whether there
    > are any compile issues with it on other platforms or compiler
    > versions.
    >
    > Linus
    >



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