[Info-vax] BASIC (and Horizon)

[Dan Cross]

In article <upe3ib$1kker$1 at dont-email.me>,
Arne Vajhøj  <arne at vajhoej.dk> wrote:
>On 1/31/2024 11:17 AM, Scott Dorsey wrote:
>> Michael S  <already5chosen at yahoo.com> wrote:
>>>
>>> The third option, the one I like least (an understatement) is use of
>>> exceptions. Despite my personal preferences, it's quite popular.
>> 
>> Exceptions can be very elegant or very inelegant... and it is entirely
>> possible to have an exception that doesn't clean anything up at all and
>> just exits and lets the operating system deal with the memory.  On many
>> systems this is a great idea because being able to exit quickly on a failure
>> is more important than people give it credit for.  On some other systems
>> that have memory management issues it can lead to leakage.
>
>It is probably a bit easier to implement exceptions in languages
>with garbage collection and a lot easier for developers to avoid
>memory leak bugs.
>
>$ type mem.cpp
>#include <iostream>
>#include <string>
>
>using namespace std;
>
>class X
>{
>private:
>     string id;
>public:
>     X(string id) { this->id = id; cout << "Allocate " << id << endl; }
>     virtual ~X() { cout << "Deallocate " << id << endl; }
>};
>
>void f2()
>{
>    throw "Houston we have a problem";
>}
>
>void f1()
>{
>    X o2("o2");
>    X *o3 = new X("o3");
>    f2();
>    delete o3;
>}
>
>int main()
>{
>     try
>     {
>         X o1("o1");
>         f1();
>     }
>     catch(char *ex)
>     {
>         cout << ex << endl;
>     }
>     return 0;
>}
>
>$ cxx mem.cpp
>$ cxxlink mem
>link  mem
>$ run mem
>Allocate o1
>Allocate o2
>Allocate o3
>Deallocate o2
>Deallocate o1
>Houston we have a problem
>$
>
>We see that o2 did get deallocated, but o3 did not get deallocated.

This is well-known in older C++ code; since C++11 one should be
using `std::unique_ptr<T>` to avoid this sort of issue.  Code
using an older dialect could look at something like the
venerable ScopeGuard as a defensive technique to guard against
leaks.
https://www.drdobbs.com/article/print?articleId=184403758&siteSectionName=cpp

	- Dan C.