What to move to?

[Björn Persson]

Florian Weimer wrote:
> Yes, Ada has some nice features.  At least there are real arrays, but 
> they are somewhat cumbersome to work with, compared to Java, Python or, 
> well, C pointers.  There are two aspects: preservation of array bounds 
> in slices (so that you have to write Table (Table'First + Offset) to 
> access the element Offset of Table, Offset ranging from 0 to 
> Table'Length - 1)

That array bounds must be preserved becomes obvious when you consider
arrays where the index type has a meaning beyond just position in the
array. If you have an array Week with a range of Monday..Sunday, and
you take the slice Week(Saturday..Sunday) and call it Weekend, then you
really don't want Weekend to suddenly have the indexes Monday and
Tuesday.

> The GNAT run-time is compiled without language-defined checks, and it 
> used to have at least one buffer overflow in the Ada part.  Many Ada 
> libraries used to follow GNAT's example and disabled the checks as well, 
> but this has changed during the last few years, it appears.  Manual 
> overflow checks are hampered by the fact that -gnato still isn't the 
> default.

Those are things that we can control in Fedora. I don't see why we
couldn't compile Libgnat with checks enabled if we wanted to – except
for the code that performs the checking i guess.

The RPM macros Gnatmake_optflags and GPRbuild_optflags contain mandatory
compiler flags that try to prevent suppression of important checks.
Unfortunately they can't override pragmas, but tools to check for
dangerous pragmas could be developed. I will add -gnato to the mandatory
compiler flags if the FPC decides so.

> Controlled types have a fixed overhead which is quite visible with small 
> objects.

Of course there is always some overhead. Do you mean that they have a
significantly larger overhead than garbage collectors have?

Björn Persson
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 190 bytes
Desc: not available
URL: <http://lists.fedoraproject.org/pipermail/devel/attachments/20130418/2457236f/attachment.sig>