[Bug fortran/20178] COMPLEX function returns incompatible with g77

["tobi at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Additional Comments From tobi at gcc dot gnu dot org  2005-02-23 20:11 -------
g77's documentation of the calling convention:
`-fno-f2c'
     Do not generate code designed to be compatible with code generated
     by `f2c' use the GNU calling conventions instead.

     The `f2c' calling conventions require functions that return type
     `REAL(KIND=1)' to actually return the C type `double', and
     functions that return type `COMPLEX' to return the values via an
     extra argument in the calling sequence that points to where to
     store the return value.  Under the GNU calling conventions, such
     functions simply return their results as they would in GNU
     C--`REAL(KIND=1)' functions return the C type `float', and
     `COMPLEX' functions return the GNU C type `complex' (or its
     `struct' equivalent).

     This does not affect the generation of code that interfaces with
     the `libg2c' library.

     However, because the `libg2c' library uses `f2c' calling
     conventions, `g77' rejects attempts to pass intrinsics implemented
     by routines in this library as actual arguments when `-fno-f2c' is
     used, to avoid bugs when they are actually called by code
     expecting the GNU calling conventions to work.

     For example, `INTRINSIC ABS;CALL FOO(ABS)' is rejected when
     `-fno-f2c' is in force.  (Future versions of the `g77' run-time
     library might offer routines that provide GNU-callable versions of
    the routines that implement the `f2c' intrinsics that may be
     passed as actual arguments, so that valid programs need not be
     rejected when `-fno-f2c' is used.)

     *Caution:* If `-fno-f2c' is used when compiling any source file
     used in a program, it must be used when compiling _all_ Fortran
     source files used in that program.



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20178