I've been reflecting on these two types of pointer. As far as I can
glean from books, void * and char * are functionally equivalent: the
key property of both is that they are pointers that can be faithfully
cast to any other pointer type.
The only difference seems to be that it is legal to perform arithmetic
on a char *, but not on a void *.
So if a char * really is just a more functional void *, why would
anyone ever use a void * in their code, instead of a char *?
Mar 19 '07
48  16973 
On Mar 19, 8:58 pm, Ian Collins <ian-n...@hotmail.co mwrote:
The whole point of that example was that it was code that used a void
* but wouldn't compile unless you added in an explicit cast.
But it didn't!
Didn't what?
*Please* don't quote signatures.
Sorry - I'll try to be careful with that in future.
just an example to illustrate a point, proof-of-context if you like.
Oops meant concept of course.
On Mar 19, 7:33 pm, Keith Thompson <k...@mib.orgwr ote:
You seem to be arguing that the compiler should shut up about implicit
conversions that don't lose any information; in other words, you want
C's type checking to be even weaker than it is. You're certainly
entitled to that opinion, but it's not one many people share. If you
want a generic pointer type, use void*. There are plenty of
mechanisms that let you be sloppy with types if you do it
deliberately; *I* want the compiler to warn me if I do it
accidentally.
That's an interesting way to put it. Maybe that's what's happening -
I've been forced to use Java for the last couple of years, which has
this horrible over-bearing strict typing, so maybe I'm reacting
against that now and trying to push the liberating flexibility that C
gives me...
However, I'm not completely sure it should be the job of the compiler
and not some optional lint tool to pick through my code for places
where I might just have meant something else. Fr************@ googlemail.com wrote:
On Mar 19, 8:58 pm, Ian Collins <ian-n...@hotmail.co mwrote:
>>>The whole point of that example was that it was code that used a void
* but wouldn't compile unless you added in an explicit cast.
But it didn't!
Didn't what?
Require an explicit cast. I used implicit conversion from void*.
--
Ian Collins. Fr************@ googlemail.com said:
On Mar 19, 7:59 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
>Francine.Ne... @googlemail.com said:
The whole point of that example was that it was code that used a
void * but wouldn't compile unless you added in an explicit cast.
But it was lousy code. Sorry, but it was. That simply isn't the kind
of place where void * is a win.
Ease up there! I wasn't submitting it to a good code contest - it was
just an example to illustrate a point, proof-of-context if you like.
Sure, but the point is that it doesn't illustrate your point well,
because it's like saying "screwdrive rs are a waste of time - I tried
hammering a nail in with one and hey, I might as well have used a
hammer". Your illustration did not provide a reason not to use void *.
It just showed that there are circumstances where void * may not be
appropriate - and we already knew that.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: rjh at the above domain, - www.
On Mar 19, 9:34 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
Francine.Ne...@ googlemail.com said:
On Mar 19, 7:59 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
Francine.Ne...@ googlemail.com said:
The whole point of that example was that it was code that used a
void * but wouldn't compile unless you added in an explicit cast.
But it was lousy code. Sorry, but it was. That simply isn't the kind
of place where void * is a win.
Ease up there! I wasn't submitting it to a good code contest - it was
just an example to illustrate a point, proof-of-context if you like.
Sure, but the point is that it doesn't illustrate your point well,
because it's like saying "screwdrive rs are a waste of time - I tried
hammering a nail in with one and hey, I might as well have used a
hammer". Your illustration did not provide a reason not to use void *.
It just showed that there are circumstances where void * may not be
appropriate - and we already knew that.
Maybe you're right! I guess the issue I have is that I'm not really
convinced that void * should exist at all. I mean, char * can double
up perfectly well as both a pointer to char and a "generic pointer",
but for some reason if you work with char * you need to do a lot of
extra explicit casting. At the very least, there seems to be a lot of
duplication between the function of void * and char *, whereas I
always think minimality and efficiency is a virtue.
On Mar 19, 9:27 pm, Ian Collins <ian-n...@hotmail.co mwrote:
Francine.Ne...@ googlemail.com wrote:
On Mar 19, 8:58 pm, Ian Collins <ian-n...@hotmail.co mwrote:
>>The whole point of that example was that it was code that used a void
* but wouldn't compile unless you added in an explicit cast.
>But it didn't!
Didn't what?
Require an explicit cast. I used implicit conversion from void*.
Well, that's true, though the net result was you saved a pair of
parentheses in your source code, and in exchange picked up an extra
pointer to carry round! Fr************@ googlemail.com wrote:
On Mar 19, 9:34 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
>>
Sure, but the point is that it doesn't illustrate your point well,
because it's like saying "screwdrive rs are a waste of time - I tried
hammering a nail in with one and hey, I might as well have used a
hammer". Your illustration did not provide a reason not to use void *.
It just showed that there are circumstances where void * may not be
appropriate - and we already knew that.
Maybe you're right! I guess the issue I have is that I'm not really
convinced that void * should exist at all. I mean, char * can double
up perfectly well as both a pointer to char and a "generic pointer",
but for some reason if you work with char * you need to do a lot of
extra explicit casting. At the very least, there seems to be a lot of
duplication between the function of void * and char *, whereas I
always think minimality and efficiency is a virtue.
No, void* serves as a generic pointer, to have char* double up (and
don't forget it used to, before void* was added to the language) adds
complexity.
void foo( char* );
Does foo() expect an generic pointer, or does foo() only expect a char*?
void* removes the ambiguity and adds clarity.
Efficiency is completely irrelevant.
--
Ian Collins. Fr************@ googlemail.com wrote:
On Mar 19, 9:27 pm, Ian Collins <ian-n...@hotmail.co mwrote:
>>Francine.Ne.. .@googlemail.co m wrote:
>>>On Mar 19, 8:58 pm, Ian Collins <ian-n...@hotmail.co mwrote:
>>>>>The whole point of that example was that it was code that used a void
>* but wouldn't compile unless you added in an explicit cast.
>>>>But it didn't!
>>>Didn't what?
Require an explicit cast. I used implicit conversion from void*.
Well, that's true, though the net result was you saved a pair of
parentheses in your source code, and in exchange picked up an extra
pointer to carry round!
The net result was I was able to use implicit conversion from void* and
didn't have to resort to (explicit, as all casts are) casting.
I'm not sure where you get the issue with the temporary pointer from.
It's just that, a temporary variable. In the trivial example you posted
it is used exactly once, in a more complex case, it would be used
wherever the passed parameter is dereferenced.
--
Ian Collins.
On 19 Mar 2007 14:13:36 -0700, Fr************@ googlemail.com wrote:
>On Mar 19, 7:33 pm, Keith Thompson <k...@mib.orgwr ote:
>You seem to be arguing that the compiler should shut up about implicit
conversions that don't lose any information; in other words, you want
C's type checking to be even weaker than it is. You're certainly
entitled to that opinion, but it's not one many people share. If you
want a generic pointer type, use void*. There are plenty of
mechanisms that let you be sloppy with types if you do it
deliberately ; *I* want the compiler to warn me if I do it
accidentally .
That's an interesting way to put it. Maybe that's what's happening -
I've been forced to use Java for the last couple of years, which has
this horrible over-bearing strict typing, so maybe I'm reacting
against that now and trying to push the liberating flexibility that C
gives me...
However, I'm not completely sure it should be the job of the compiler
and not some optional lint tool to pick through my code for places
where I might just have meant something else.
With most compilers, the "linting" level is controllable. Find a set
of switches you like. However, keep in mind that compilers actually
aren't always smart enough to distinguish warnings from errors.
--
Al Balmer
Sun City, AZ This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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