Thread: What is this constant?

  1. #1
    programmer hacker DevZero's Avatar
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    What is this constant?

    I looked in the Include stdlib.h and I saw there such code:
    Code:
    extern int system (const char *__command) __wur;
    I'm interested in; __wur.
    I searched on the Internet and on includes but did not find anything, what is it?

  2. #2
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    Something internal to the compiler or library implementation.

    If you really wish to know find a site that supports your compiler and ask there.
    Or, at least post your compiler information in this thread and maybe someone will be able to answer the question.

    Tim S.
    "...a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are,in short, a perfect match.." Bill Bryson

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    programmer hacker DevZero's Avatar
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    information

    My gcc: 4.9.2-10 gnueabihf

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    It tells the compiler to warn about an unused result.
    __wur

  5. #5
    Registered User rstanley's Avatar
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    re: __wur

    From a Bug Report:
    Unfortunately glibc marks fwrite --- but oddly not the other stdio
    output functions --- with __wur (which expands to
    __attribute__((__warn_unused_result__)) when optimization is enabled
    and the _FORTIFY_SOURCE feature is in use).
    From the GNU Website:
    The warn_unused_result attribute causes a warning to be emitted if a caller of the function with this attribute does not use its return value. This is useful for functions where not checking the result is either a security problem or always a bug, such as realloc.

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