[1/8] gdb: Add $_cimag and $_creal internal functions

  * Eli Zaretskii <eliz@gnu.org> [2019-03-18 19:20:26 +0200]:

> > From: Andrew Burgess <andrew.burgess@embecosm.com>
> > Cc: Richard Bunt <Richard.Bunt@arm.com>,	Andrew Burgess <andrew.burgess@embecosm.com>
> > Date: Mon, 18 Mar 2019 12:52:16 +0000
> > 
> > gdb/ChangeLog:
> > 
> > 	* NEWS: Mention new internal functions.
> > 	* dwarf2read.c (dwarf2_init_complex_target_type): New function.
> > 	(read_base_type): Use dwarf2_init_complex_target_type.
> > 	* value.c (creal_internal_fn): New function.
> > 	(cimag_internal_fn): New function.
> > 	(_initialize_values): Register new internal functions.
> > 
> > gdb/doc/ChangeLog:
> > 
> > 	* gdb.texinfo (Convenience Funs): Document '$_creal' and
> > 	'$_cimag'.
> 
> The documentation parts are okay, with a couple of comments:
> 
> > +@item $_cimag(@var{value})
> > +@findex $_cimag@r{, convenience function}
> > +Return the imaginary part of a complex number @var{value}.
> > +
> > +The type of the imaginary part depends on the type of the complex
> > +number, a @code{float complex} will return an imaginary part of type
> > +@code{float}.
> > +
> > +@item $_creal(@var{value})
> > +@findex $_creal@r{, convenience function}
> > +Return the real part of a complex number @var{value}.
> > +
> > +The type of the real part depends on the type of the complex number, a
> > +@code{float complex} will return an real part of type @code{float}.
> 
> There's no need to repeat the sentence about the type being dependent
> on the original type; you can say that just once for both.

Thanks for your feedback.

What I've done is group the @item entries for $_creal and $_cimag
together.  My thinking is that if a user looks up either of these then
the documentation should be complete.  If I left the @item entries
separate, and removed the sentence as you suggested then I think I'd
have to add a cross reference.

Hopefully this will be OK.

All your other feedback has been addressed.  A new version of the
patch is below for your consideration.

Thanks,
Andrew

> 
> Also, the "a @code{float complex} will return ..." part is better
> preceded by "e.g.", as this is an example, right?
> 
> And finally, "a real part", not "an real part".
> 
> > +Return the real part of a complex number, the type depends on the\n\
> > +type of a complex number."),
>            ^
> "the", not "a".
> 
> > +Return the imaginary part of a complex number, the type depends on the\n\
> > +type of a complex number."),
> 
> Likewise.

---

    gdb: Add $_cimag and $_creal internal functions

    Add two new internal functions $_cimag and $_creal that extract the
    imaginary and real parts of a complex value.

    These internal functions can take a complex value of any type 'float
    complex', 'double complex', or 'long double complex' and return a
    suitable floating point value 'float', 'double', or 'long double'.
    So we can now do this:

        (gdb) p z1
        $1 = 1.5 + 4.5 * I
        (gdb) p $_cimag (z1)
        $4 = 4.5
        (gdb) p $_creal (z1)
        $4 = 1.5

    The components of a complex value are not strictly named types in
    DWARF, as the complex type is itself the base type.  However, once we
    are able to extract the components it makes sense to be able to ask
    what the type of these components is and get a sensible answer back,
    rather than the error we would currently get.  Currently GDB says:

        (gdb) ptype z1
        type = complex double
        (gdb) p $_cimag (z1)
        $4 = 4.5
        (gdb) ptype $
        type = <invalid type code 9>

    With the changes in dwarf2read.c, GDB now says:

        (gdb) ptype z1
        type = complex double
        (gdb) p $_cimag (z1)
        $4 = 4.5
        (gdb) ptype $
        type = double

    Which seems to make more sense.

    gdb/ChangeLog:

            * NEWS: Mention new internal functions.
            * dwarf2read.c (dwarf2_init_complex_target_type): New function.
            (read_base_type): Use dwarf2_init_complex_target_type.
            * value.c (creal_internal_fn): New function.
            (cimag_internal_fn): New function.
            (_initialize_values): Register new internal functions.

    gdb/doc/ChangeLog:

            * gdb.texinfo (Convenience Funs): Document '$_creal' and
            '$_cimag'.

    gdb/testsuite/ChangeLog:

            * gdb.base/complex-parts.c: New file.
            * gdb.base/complex-parts.exp: New file.

[1/8] gdb: Add $_cimag and $_creal internal functions

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