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re PR fortran/31160 (%VAL and related features need to be documented.)

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2007-03-31  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/31160
	* gfortran.texi: Add a section for the %VAL, %REF and %LOC
	extensions.

From-SVN: r123383
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Paul Thomas 2007-03-31 16:42:58 +00:00
parent c9516c38e3
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6
gcc/fortran/ChangeLog
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@ -1,3 +1,9 @@
2007-03-31 Paul Thomas <pault@gcc.gnu.org>
PR fortran/31160
* gfortran.texi: Add a section for the %VAL, %REF and %LOC
extensions.
2007-03-30 Rafael Avila de Espindola <espindola@google.com>
* trans-types.c (gfc_signed_or_unsigned_type): Remove.

39
gcc/fortran/gfortran.texi
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@ -808,6 +808,7 @@ of extensions, and @option{-std=legacy} allows both without warning.
* Cray pointers::
* CONVERT specifier::
* OpenMP::
* Argument list functions::
@end menu
@node Old-style kind specifications
@ -1288,6 +1289,44 @@ For details refer to the actual
@uref{http://www.openmp.org/drupal/mp-documents/spec25.pdf,
OpenMP Application Program Interface v2.5} specification.
@node Argument list functions
@section Argument list functions %VAL, %REF and %LOC
@cindex Argument list functions %VAL, %REF and %LOC
GNU Fortran supports argument list functions @code{%VAL}, @code{%REF}
and @code{%LOC} statements, for backward compatibility with g77.
It is recommended that these should be used only for code that is
accessing facilities outside of GNU Fortran, such as operating system
or windowing facilities. It is best to constrain such uses to isolated
portions of a program--portions that deal specifically and exclusively
with low-level, system-dependent facilities. Such portions might well
provide a portable interface for use by the program as a whole, but are
themselves not portable, and should be thoroughly tested each time they
are rebuilt using a new compiler or version of a compiler.
@code{%VAL} passes a scalar argument by value, @code{%REF} passes it by
reference and @code{%LOC} passes its memory location. Since gfortran
already passes scalar arguments by reference, @code{%REF} is in effect
a do-nothing. @code{%LOC} has the same effect as a fortran pointer.
An example of passing an argument by value to a C subroutine foo.:
@smallexample
C
C prototype void foo_ (float x);
C
external foo
real*4 x
x = 3.14159
call foo (%VAL (x))
end
@end smallexample
For details refer to the g77 manual
@uref{http://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/index.html#Top}.
Also, the gfortran testsuite c_by_val.f and its partner c_by_val.c are
worth a look.
@c ---------------------------------------------------------------------
@c Intrinsic Procedures
@c ---------------------------------------------------------------------