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From: Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: ok, I have more info on problem at hand
Date: 4 Sep 2000 10:40:46 GMT
Organization: Aachen University of Technology (RWTH)
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Xref: news.mv.net comp.os.msdos.djgpp:103152

James W Sager Iii <sager+@andrew.cmu.edu> wrote:
[...]
> int *i;
> i=malloc(20);
> i=realloc(100);

> errors:
>  Error: ANSI C++ forbids implicit conversion from `void *' in assignment
>  Error: ANSI C++ forbids implicit conversion from `void *' in assignment

This is an example of one of the areas in which modern ANSI/ISO
standardized C++ will _refuse_ to compile programs that are perfectly
valid in ANSI C, and used to be valid in many C++ compilers that were
released before the C++ language finally managed to become
standardized.

I seem to remember there's some gcc command line option (-relax or
something similarly named) that will reduce such errors to warnings.

Setting that aside, you have these alternatives:

1) "proper C++ coding" would have you use 'new' instead of malloc().
   The backside is that there is no equivalent of realloc(), for a
   C++ array.
2) use advanced C++ classes like the STL vector<int> thing to model
   dynamically growable/shrinkable arrays.
3) stick to malloc()/realloc()/free(). In this case, you'll have to
   *cast* the pointer returned by them. I.e., you have to write:
	
	i = (int *) malloc(20);
	i = (int *) realloc(100);

    The same idiom is considered a bad idea by the C gurus, but in
    C++, it's a necessity. The underlying change is that due to 
    classes and polymorphism, C++ had to do away with the concept of
    fully automatic pointer conversion to and from 'void *'.

-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.