Re: POSIX_C_SOURCE

From: Malcolm Kay (malcolm.kay_at_internode.on.net)
Date: 09/01/03

  • Next message: Ruben van Staveren: "Re: kernel: wi0: timeout in wi_seek" 
    To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>, troy@twisted.net
Date: Mon, 1 Sep 2003 12:17:13 +0930

    On Sun, 31 Aug 2003 02:19, Garrett Wollman wrote:
    > In article <20030830161813.GA28890@twisted.net> you write:
    > >Any chance that someone will finally commit the fixes to prevent the
    > >POSIX_C_SOURCE warnings from showing up? I saw a number of posts on this
    > >topic, but it still seems like it's not "officially committed"
    > >
    > >/usr/include/sys/cdefs.h:273: warning: `_POSIX_C_SOURCE' is not defined
    > >/usr/include/sys/cdefs.h:279: warning: `_POSIX_C_SOURCE' is not defined
    >
    > The warnings are wrong,[1] so you should probably ask the GCC people
    > about that.
    >
    > -GAWollman
    >
    > [1] That is to say, any identifier used in a preprocessor expression
    > (after macro expansion) is defined to have a value of zero, and GCC
    > should not be complaining about this.
    >

    The warnings are only wrong in your personal interpretation of right and
    wrong. Many gcc options generate warnings with legal C source and this is
    permitted by the C standard (whether or not it is controlled by a compiler
    option) provided it does not prevent generation of correct code.

    The warning is true: that is _POSIX_C_SOURCE is not defined (and is evaluated
    in an #if preprocessor statement).

    The warning only appears when -Wundef option is used which relates
    specifically to this circumstance. GCC people surely cannot be criticised
    for an option that works precisely as documented.

    No-one individually has it wrong.
    The problem is one of incompatibility between the header files and the
    compiler options selected. Since the compiler options are probably set for a
    range of environments it is probably best to adapt the system header files to
    circumvent the difficulty.

    Malcolm Kay

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