gcc bug ?

[Phil Edwards]

On Mon, Nov 13, 2000 at 11:47:48AM +1100, LOOK, Peter wrote:
> 
> Enclosed please find a simple program eg3_2_1.cpp which is an example in
> P.96 of "Teach Yourself C++" 3rd Edition by Herbert Schildt.

As a side note, I feel ethically compelled to mention that Schildt's books
are considered to be of poor quality by many members of the C++ community.
If you want a "teach yourself" book, you might try one by Jesse Liberty.


> But, I use gcc to compile. It WORKS, no complaint. When I run the execution
> file. It works fine. It should be failed to compile because wrong type
> matching !! Is it a bug ? 

No.  There is no compiler bug, and the code is valid C++.  You are seeing
the results of implicit type conversion, via conversion constructors.

What happens is that the language allows an int to be implicitly converted
into a samp by way of the single-argument constructor, samp::samp(int).
When you try passing an int to sqr_it, the compiler constructs a temporary
samp object using the constructor.

Change the constructor to read

    samp (int n) { cout << "here I am\n"; i = n' }

and you will see it being called.

You can prevent implicit constructor conversion by using the 'explicit'
keyword in front of those kinds of constructors.

Also, as another side note:

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That sort of thing is considered rather poor form on a public,
publicly-archived mailing list.  Just FYI, nothing personal.

Phil

-- 
pedwards at disaster dot jaj dot com  |  pme at sources dot redhat dot com
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The gods do not protect fools.  Fools are protected by more capable fools.