Re: C++ Should not be used for Medical Devices

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

Dr. Robert Leif <rleif@RLEIF.COM> wrote in article
<3.0.32.19970119225145.006fce98@mail.4dcomm.com>...
The best help you can get from Comp.Lang.Ada, where this appeared, is not
how to find the best C++ Debugger; but, the simple statement, Try Ada 95.

Date:    Thu, 16 Jan 1997 22:22:29 -0500
From:    Macarthur Drake <drake@BME.RI.CCF.ORG>
Subject: Help you C++ Debuggers!

I am in the mist of completing a major piece of code in C++. However I
keep comming across a particularly difficult bug. Can you help?

        I am simply trying to declare a three D array:

float objects[9000][10][10];

Hi Macarthur,

I cannot agree too strongly with Robert Leif that you should use Ada95 for
safety-critical systems.

However, there is one aspect of the problem -- i.e., the runtime
segmentation faults which could happen even with Ada, since you are
declaring the variable on the stack, or in the static data segment of your
program (you didn't provide enough context to show which).  The size of
your array amounts to 3,600,000 bytes and could be more than is allowed by
the default stack size of your program.

Dynamic allocation (as you suggest) is the solution to the run-time
problem.

E.g., in C/C++ you could write:
#define DIM_1 9000
#define DIM_2 10
#define DIM_3 10
void main (void)
{
float * * * objects;
objects = malloc (
    DIM_1 * DIM_2 * DIM_3 * sizeof (float)
    );
exit (0);
}

Or in Ada, you could write
procedure Macarthur is
  Dim_1 : constant Natural := 9000;
  Dim_2 : constant Natural := 10;
  Dim_3 : constant Natural := 10;
  type Object_Array_Type is
       array (0 .. Dim_1 - 1, 0 .. Dim_2 - 1, 0 .. Dim_3 - 1) of Float;
   type Object_Array_Access_Type is access Object_Array_Type;
   Objects : Object_Array_Access_Type := new Object_Array_Type;
 begin
   null;
 end Macarthur;

In Ada you would raise an exception any time you attempted to access
outside the array.

As to why the compile-time failures, it's difficult to say without knowing
the compiler/platform, but maybe it's because the compiler is written in C?

Hope this helps

-- 
David C. Hoos, Sr.,
http://www.dbhwww.com
http://www.ada95.com