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Re: OT: Language War (Re: "C" Manual)

On Thu, Jan 03, 2002 at 09:39:09PM -0600, Gary Turner wrote:
| On Thu, 03 Jan 2002 17:34:00 -0600 (CST), Richard Cobbe wrote:
| >
| >Lo, on Thursday, January 3, Erik Steffl did write:
| >
| >> what's the difference? the point is you can assign almost anything to
| >> anything, and yet there is no segfault - i.e. the strength of types has
| >> nothing (sort of) to do with segfaults... the resource allocation is
| >> crucial...
| >
| >Type safety (plus dynamic allocation) implies advanced memory
| >management.  The converse is not true: you can slap Boehm's conservative
| >GC onto a C++ program, but you can still get segmentation faults:
| >
| >    char str[] = { 'b', 'a', 'd', ' ', 's', 't', 'r', 'i', 'n', 'g' };
| >    // note the lack of a terminating '\0'!
| >    cout << str;
| >
| >No allocation issues involved.  As Ben Collins pointed out elsewhere in
| >this thread (bit of a tree-shaped thread, isn't it?), this won't
| >necessarily cause a segfault, but it can.  It's also a violation of
| >type-safety: cout expects a null-terminated string, and as far as the
| >compiler is concerned, str fits this.  However, there's no runtime check
| >in the output routine to verify that this is, in fact, the case.  Ooops.
| Neophyte that I am, I feel like I'm bringing a knife to this gunfight.
| This example looks to be a cheat, in that you've defined an array and
| then treated it as a string (legal).  Had you defined a string, it would
| be null terminated and index addressable.

He did define a string.  In C++ there are 3 ways of defining a string
(in C there are 2).  There is "char[]", "char*" and "std::string".
The latter is the best way because it provides the most protection.

| The fact that you *can* screw up doesn't mean you have to.

True, but when choosing a language for a given project, wouldn't you
rather use one that gives you fewer guns to shoot yourself with?  I
know I would :-).  (this is not to say that C is not a good language,
but it does have its place)

| >Therefore, I claim that type safety is a more fundamental concept than
| >resource mangement.
| Is there a difference?  Again, my ignorance knowing no bounds.  Doesn't
| the type define the required allocation?

A given type will have certain allocation requirments (ie size, which
is why a C++ class can't contain a non-pointer to a not-yet-defined
class or to a class that contains the current class).

| In the example above, is it a type, or allocation error if the
| *programmer* decides to access str[10]?  (If I counted right, that's
| the next byte after the array bloc.)

I think that would be an allocation error since it is illegal to
access memory outside the allocated bounds.  



A Microsoft Certified System Engineer is to information technology as a
McDonalds Certified Food Specialist is to the culinary arts.
        Michael Bacarella commenting on the limited value of certification.

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