[Bug ada/34117] New: Please enable range checks by default (-gnato)

[Bug ada/34117] New: Please enable range checks by default (-gnato)

[ludovic at ludovic-brenta dot org]

By default, GCC is not an Ada compiler and has not been one for years, because
range checks are disabled by default and require an explicit switch (-gnato). 
The rationale, as I understand it, was that range checks were expensive in
terms of CPU usage.

However, the rationale is much less valid now that CPUs are more powerful and,
more importantly, thanks to improvements in GCC's range checks elimination.

The drawback of the current situation is that almost every new user of Ada, at
some point, is surprised because they don't get the expected Constraint_Error. 
In other words, GCC fails the Law of Least Astonishment.

Range checks can always be disabled explicitly with -gnatp or pragma Suppress.

Therefore: please enable range checks by default.

I'm going to file a separate bug report for stack checking, which is also
required by the Ada Reference Manual.


-- 
           Summary: Please enable range checks by default (-gnato)
           Product: gcc
           Version: 4.2.2
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: ada
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ludovic at ludovic-brenta dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] Please enable range checks by default (-gnato)

[jeff at thecreems dot com]

------- Comment #1 from jeff at thecreems dot com  2007-11-16 14:27 -------
Seems like a good idea. Since we often say that correctness should come before
performance when it comes to optimization, it has always seemed odd to me that
performance was the default mode of operation.

We can complain all we want that users should read the manual before they start
using the compiler but the fact is they don't and probably never will.

I do wonder if perhaps a new flag that just disables range checking to get the
'old' behavior would be warranted?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] Please enable range checks by default (-gnato)

[niklas dot holsti at tidorum dot fi]

------- Comment #2 from niklas dot holsti at tidorum dot fi  2007-11-16 18:07 -------
(In reply to comment #1)
> Seems like a good idea.

I think so, too.

> I do wonder if perhaps a new flag that just disables range checking to get the
> 'old' behavior would be warranted?

Yes, that would definitely be a good help for the transition.


-- 

niklas dot holsti at tidorum dot fi changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |niklas dot holsti at tidorum
                   |                            |dot fi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] Please enable range checks by default (-gnato)

[listor3 dot rombobeorn at tdcpost dot se]

------- Comment #3 from listor3 dot rombobeorn at tdcpost dot se  2007-11-16 23:16 -------
I've never seen any numbers on just how expensive -gnato is, but provided that
the cost is moderate I think it should be on by default.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] Please enable range checks by default (-gnato)

[bauhaus at futureapps dot de]

------- Comment #4 from bauhaus at futureapps dot de  2007-11-20 14:49 -------
I can't resist pointing out that right now I am seeing an
update to widely used free software where once again an integer
overflow is creating a security hole in the system. (CVE-2007-4619)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] Please enable overflow checks by default (-gnato)

[charlet at gcc dot gnu dot org]

------- Comment #5 from charlet at gcc dot gnu dot org  2007-11-21 06:55 -------
This report is confused: range checking is enabled by default.

-gnato is about overflow checking, not range checking.

Arno


-- 

charlet at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Please enable range checks  |Please enable overflow
                   |by default (-gnato)         |checks by default (-gnato)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117

[Bug ada/34117] enable overflow checks by default (-gnato)

[ebotcazou at gcc dot gnu dot org]

-- 

ebotcazou at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-03-08 08:58:26
               date|                            |
            Summary|Please enable overflow      |enable overflow checks by
                   |checks by default (-gnato)  |default (-gnato)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34117