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(standards.info)Conditional Changes

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Conditional Changes
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   C programs often contain compile-time `#if' conditionals.  Many
changes are conditional; sometimes you add a new definition which is
entirely contained in a conditional.  It is very useful to indicate in
the change log the conditions for which the change applies.

   Our convention for indicating conditional changes is to use square
brackets around the name of the condition.

   Here is a simple example, describing a change which is conditional
but does not have a function or entity name associated with it:

     * xterm.c [SOLARIS2]: Include string.h.

   Here is an entry describing a new definition which is entirely
conditional.  This new definition for the macro `FRAME_WINDOW_P' is
used only when `HAVE_X_WINDOWS' is defined:

     * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined.

   Here is an entry for a change within the function `init_display',
whose definition as a whole is unconditional, but the changes themselves
are contained in a `#ifdef HAVE_LIBNCURSES' conditional:

     * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent.

   Here is an entry for a change that takes affect only when a certain
macro is _not_ defined:

     (gethostname) [!HAVE_SOCKETS]: Replace with winsock version.