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| author | Paul Thomas <pault@gcc.gnu.org> | 2007-03-31 16:42:58 +0000 |
|---|---|---|
| committer | Paul Thomas <pault@gcc.gnu.org> | 2007-03-31 16:42:58 +0000 |
| commit | d60e76db50467899935a6738a56af8871d33a789 (patch) | |
| tree | 7d470ade8ba2b23b23b184fcfc2c89c02a6a6c2d | |
| parent | c9516c38e3ea4a028efafe349142638800e0212e (diff) | |
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re PR fortran/31160 (%VAL and related features need to be documented.)
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
| -rw-r--r-- | gcc/fortran/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/fortran/gfortran.texi | 39 |
2 files changed, 45 insertions, 0 deletions
diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog index 1697e44..63c8bb7 100644 --- a/gcc/fortran/ChangeLog +++ b/gcc/fortran/ChangeLog @@ -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. diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi index 52b4c2c..5f31585 100644 --- a/gcc/fortran/gfortran.texi +++ b/gcc/fortran/gfortran.texi @@ -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 --------------------------------------------------------------------- |