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.Dd December 20, 2012
.Dt STANDARDS 7
.Os
.Sh NAME
.Nm standards
.Nd standards supported by DragonFly
.Sh SYNOPSIS
.Fd "#define _XOPEN_SOURCE 600"
.Pp
.In sys/cdefs.h
.Sh DESCRIPTION
A number of
.Dq feature test macros ,
namely
.Dv _POSIX_C_SOURCE
and
.Dv _XOPEN_SOURCE ,
can be used by applications to indicate desired sets of features (beyond
those specified by the C standard) in the programming environment supplied by
.Dx .
These macros determine which prototypes are exposed by header files and so on.
.Pp
If neither
.Dv _POSIX_C_SOURCE
and
.Dv _XOPEN_SOURCE
are set, the programming environment defaults to
.St -susv3 .
In addition, a number of
.Bx
specific prototypes, definitions etc.\& are made visible.
.Ss POSIX Standards (_POSIX_C_SOURCE)
The value of the
.Dv _POSIX_C_SOURCE
macro determines which
.Tn POSIX
standard the programming environment conforms to.
.Bl -tag -width ".Li 199009"
.It Li 1
Make definitions conforming to
.St -p1003.1-90
visible.
Implies
.St -isoC-90 .
.It Li 2
Additionally, make definitions conforming to
.St -p1003.2-92
visible.
.It Li 199009
Same as
.Li 1 .
.It Li 199209
Same as
.Li 2 .
.It Li 199309
Additionally, make definitions conforming to
.St -p1003.1b-93
visible.
.It Li 199506
Additionally, make definitions conforming to
.St -p1003.1c-95
visible.
.It Li 200112
Additionally, make definitions conforming to
.St -p1003.1-2001
visible.
Implies
.St -isoC-99 .
This is the default.
.It Li 200809
Additionally, make definitions conforming to
.St -p1003.1-2008
visible.
Implies
.St -isoC-99 .
.El
.Pp
Defining
.Dv _POSIX_C_SOURCE
to any value lower than
.Li 199009
(other than
.Li 1
or
.Li 2 )
makes it default to
.Li 198808
which makes definitions conforming to
.St -p1003.1-88
visible.
No C standard is implied in this case.
.Pp
Defining the obsolete
.Dv _POSIX_SOURCE
macro without defining
.Dv _POSIX_C_SOURCE
is equivalent to defining
.Dv _POSIX_C_SOURCE
to
.Li 198808 .
.Ss X/Open CAE Specifications (_XOPEN_SOURCE)
The value of the
.Dv _XOPEN_SOURCE
macro determines which X/Open CAE specification the programming
environment conforms to.
.Bl -tag -width ".Li 500"
.It Li 500
Make definitions conforming to the
.St -susv2
visible.
Implies defining
.Dv _POSIX_C_SOURCE
to
.Li 199506 .
.It Li 600
Make definitions conforming to the
.St -susv3
visible.
Implies defining
.Dv _POSIX_C_SOURCE
to
.Li 200112 .
This is the default.
.It Li 700
Make definitions conforming to
.St -p1003.1-2008
and to the corresponding XSI extensions visible.
.El
.Pp
If both CAE and POSIX conformance is required, only
.Dv _XOPEN_SOURCE
can be set.
.\".Ss Miscellaneous Macros
.\".Dv _ANSI_SOURCE
.\".Dv _C99_SOURCE
.\".Dv _DRAGONFLY_SOURCE
.\".Dv _NETBSD_SOURCE
.Sh SEE ALSO
.Bl -tag -width xx
.It Pa http://pubs.opengroup.org/onlinepubs/9699919799/
.St -p1003.1-2008
.It Pa http://pubs.opengroup.org/onlinepubs/009695399/
.St -p1003.1-2004
.It Pa http://pubs.opengroup.org/onlinepubs/7908799/
.St -susv2
.It Pa http://pubs.opengroup.org/onlinepubs/9695969499/toc.pdf
.St -xsh4.2
.El
.Sh HISTORY
A
.Nm
manual page first appeared in
.Dx 2.7 .