Re: Commercial C To Ada 95 compiler

[Jim Rogers <jimmaureenrogers@worldnet.att.net>]

SteveD wrote:

> "Wes Groleau" <wesgroleau@despammed.com> wrote in message
> news:3D0116F3.7254E263@despammed.com...
> 
> [snip]
> 
>>A direct translation to Ada will reveal
>>some bugs at compile time.  And the developers
>>are looking at a language they can read
>>when they fix those bugs.
>>
> 
> I disagree.  A direct translation to Ada should not reveal any bugs at
> compile time.  In fact it should replicate memory leaks and errant pointers.
> If it doesn't do so, it is not a direct translation.


You may be very wrong here. Ada compilers tend to identify many more
errors at compile time than C compilers. This means that code
which compiles without error on a C compiler, when directly translated
to Ada, will may not compile.

One simple example is indexing past the end of an array.
C compilers simply will not catch this problem. Ada compilers will.

On the whole, direct translation may not be possible. C uses
implicit conversion between integer and floating point types.
Ada provides no such implicit conversion. You will at least need
to make all implicit C conversions explicit in Ada.

Another incompatibility is trying to reference the control
variable in a "for" loop outside the scope of the "for" loop.
This is impossible in Ada and not uncommon in C. The C compiler
will allow this. The Ada compiler will not.

Your example of "direct" translation of a C for loop with a null
body to an Ada while loop is a good approximation of the problem,
but not, IMHO, a direct translation. A direct translation would have
the C code also using a while loop. Ada for loops simply cannot
demonstrate this error. Any attempt to do so will create a
compiler error.

Jim Rogers