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Bug#202197: libc6-dev: _POSIX_MESSAGE_PASSING should be defined to -1



Package: libc6-dev
Version: 2.3.2-1
Severity: normal

In /usr/include/bits/posix_opt.h, _POSIX_MESSAGE_PASSING is explicitly
undefined. It has the following comment:

  /* POSIX message queues are not yet supported.  */
  #undef	_POSIX_MESSAGE_PASSING

SUSv3 says the following:

  The following symbolic constants, if defined in <unistd.h>, shall
  have a value of -1, 0, or greater, unless otherwise specified below.
  If these are undefined, the fpathconf(), pathconf(), or sysconf()
  functions can be used to determine whether the option is provided for
  a particular invocation of the application.
  
  If a symbolic constant is defined with the value -1, the option is not
  supported. Headers, data types, and function interfaces required only for
  the option need not be supplied. An application that attempts to use
  anything associated only with the option is considered to be requiring an
  extension.


Therefore, the correct thing to do if the option is not supported is to
define it to -1. When testing for a SUSv3 compliant wrapper library, I
depend on the value of this particular constant in deciding whether or
not to include <mqueue.h>, which does not exist. Because including a
nonexistent header causes problems (such as failed compilation), I need
to know at compile time whether this extension is supported so I don't
get screenfuls of compilation errors. If you do explicitly undefine an
extension variable, please include appropriate headers with function
definitions, types, macros, constants, etc, so that it can be detected
at runtime whether or not the program or library is able to use those
functions.

-- System Information:
Debian Release: testing/unstable
Architecture: i386
Kernel: Linux stonewall 2.4.21-2-k7 #1 Sat Jul 5 03:47:02 EST 2003 i686
Locale: LANG=C, LC_CTYPE=C

Versions of packages libc6-dev depends on:
ii  libc6                         2.3.2-1    GNU C Library: Shared libraries an

-- no debconf information


-- 
Brian M. Carlson <sandals@crustytoothpaste.ath.cx> 0x560553e7
"Let us think the unthinkable, let us do the undoable. Let us prepare
 to grapple with the ineffable itself, and see if we may not eff it
 after all." --Douglas Adams

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