Why on this list, of all the possible places in Creation? It's a great
and important topic, but have you found no other, more appropriate forum?
On 03/28/2016 02:50 AM, Edward Bartolo wrote:
> Hi,
>
> As the title of the email indicates, I am doing some exercises to make
> sense out of C pointer
Edward Bartolo:
...
> However, C pointer syntax is proving to be as unintuitive as it can
> be.
...
> I want to understand, as opposed to knowing by rote, the
> mechanism why they work.
...
///
I think one source of confusion re. c-pointers is that they are
declared "as they are used", but you mi
Edward Bartolo writes:
> As the title of the email indicates, I am doing some exercises to make
> sense out of C pointer syntax. I have been using pointers for as long
> as I have been programming without issues, apart from the usual
> initial programmatic errors when new code is run for the first
k...@aspodata.se writes:
[...]
> To exemplify the "as they are used" statement, take a function pointer
> declaration:
>
> void (*log_func)(int priority, const char *format);
>
> here you cannot conveniently move the "*" to the "void" so it will look
> like a "pointer" declaration; it declares
Edward Bartolo:
...
> I am attaching two short C programs that I created and which I tested
> to work although the mechanism by which they work is still somewhat
> hazy to me.
...
Some comments on test101.c
#include
void change_value(void* ptr) {
*((int*) ptr) = 2000;
}
int main() {
k...@aspodata.se writes:
[...]
> With pointers, you have to handle the special case of null pointers.
> I'm assuming you are omitting it here for brevity, but generally
> change_value() should be something like:
>
> void change_value(int* ptr) {
> if (!ptr) return;
> *ptr = 2000;
> }
It
Rainer Weikusat:
...
> One thing to note here: Every C pointer is really a pointer to an array
> of values, although the size of the array may just be one.
...
I thought it was the other way around, a pointer is just an address to
some (a single) memory location which can be part of an array, I'd
Rainer Weikusat:
> k...@aspodata.se writes:
...
> > To exemplify the "as they are used" statement, take a function pointer
> > declaration:
> >
> > void (*log_func)(int priority, const char *format);
> >
> > here you cannot conveniently move the "*" to the "void" so it will look
> > like a "poin
Rainer Weikusat:
> k...@aspodata.se writes:
...
> > With pointers, you have to handle the special case of null pointers.
> > I'm assuming you are omitting it here for brevity, but generally
> > change_value() should be something like:
> >
> > void change_value(int* ptr) {
> > if (!ptr) return;
>
Because we're developing software.
On Mon, 28 Mar 2016 06:03:13 -0400
Boruch Baum wrote:
> Why on this list, of all the possible places in Creation? It's a great
> and important topic, but have you found no other, more appropriate
> forum?
>
> On 03/28/2016 02:50 AM, Edward Bartolo wrote:
> > H
On Mon, 28 Mar 2016 14:51:19 +0200 (CEST)
k...@aspodata.se wrote:
> Rainer Weikusat:
> ...
> > One thing to note here: Every C pointer is really a pointer to an
> > array of values, although the size of the array may just be one.
> ...
>
> I thought it was the other way around, a pointer is jus
On Mon, 28 Mar 2016 12:28:03 +0200 (CEST)
k...@aspodata.se wrote:
> To exemplify the "as they are used" statement, take a function
> pointer declaration:
>
> void (*log_func)(int priority, const char *format);
>
> here you cannot conveniently move the "*" to the "void" so it will
> look like a
Hi Boruch,
On 03/28/2016 02:00 PM, Boruch Baum wrote:
Why on this list, of all the possible places in Creation? It's a great
and important topic, but have you found no other, more appropriate forum?
This is an appropiate list to argue about pointers. Have a look at the
code of some projects
Steve Litt:
...
> Years ago I gave up trying to logically explain the syntax of function
> pointers, which are so essential for callbacks and pseudo-oop, and just
> memorized the idiom.
>
> Edition 1 of K&R had an actual algorithm by which one could dissect any
> lvalue (thing that can appear on t
char *p;
p="01234"; /* skeezy, but makes the point */
Warning! Here "p" is pointing to nowhere, you don't know which memory
locations are writing to.
char *p;
*p=malloc...*
p="01234"; /* skeezy, but makes the point */
On Mon, Mar 28, 2016 at 12:59 PM, Steve Litt
wrote:
> On Mon, 28 Mar 2016
Emiliano Marini writes:
> char *p;
> p="01234"; /* skeezy, but makes the point */
>
> Warning! Here "p" is pointing to nowhere, you don't know which memory
> locations are writing to.
The 'memory location' (if any) reserved for the pointer p itself by the
compiler, IOW, this is totally correct.
The main difference here is where you are storing the value "2000".
In the first example, p is located in addresses belonging to "main" memory
space (the stack presumably, beacuse "main" is the first function called
upon start). You are passing the memory address of p (where p is located)
to t
You're right.
On Mon, Mar 28, 2016 at 2:04 PM, Rainer Weikusat <
rainerweiku...@virginmedia.com> wrote:
> Emiliano Marini writes:
> > char *p;
> > p="01234"; /* skeezy, but makes the point */
> >
> > Warning! Here "p" is pointing to nowhere, you don't know which memory
> > locations are writing
I was wrong because in this examples p was a pointer to int. Sorry, I was
thinking on something like this:
int *p;
*p = 0;
Cheers,
Emiliano.
On Mon, Mar 28, 2016 at 2:16 PM, Emiliano Marini wrote:
> You're right.
>
> On Mon, Mar 28, 2016 at 2:04 PM, Rainer Weikusat <
> rainerweiku...@virginmed
k...@aspodata.se writes:
> Rainer Weikusat:
> ...
>> One thing to note here: Every C pointer is really a pointer to an array
>> of values, although the size of the array may just be one.
> ...
>
> I thought it was the other way around, a pointer is just an address to
> some (a single) memory locati
On 28/03/2016 15:35, Steve Litt wrote:
On Mon, 28 Mar 2016 06:03:13 -0400
Boruch Baum wrote:
Why on this list, of all the possible places in Creation? It's a great
and important topic, but have you found no other, more appropriate
forum?
> Because we're developing software.
I'd have to say
Roger Leigh writes:
> On 28/03/2016 15:35, Steve Litt wrote:
>> On Mon, 28 Mar 2016 06:03:13 -0400
>> Boruch Baum wrote:
>>
>>> Why on this list, of all the possible places in Creation? It's a great
>>> and important topic, but have you found no other, more appropriate
>>> forum?
>
>> Because we
Hi,
Thanks for dedicating some of your time to answer me. I used:
void change_value(void** ptr)
Because I wanted to enable myself to allocate memory for the pointer
inside the function, therefore I needed a pointer to a pointer of type
void. Void allows such a function to handle different data t
Short version: From the screen that lets the user select specific system
components to install, eg. XFCE, print server, SSH server, when I tabbed
to the selection "go back" with the intention of getting the main menu,
what happened instead was the installer began downloading "1173
packages". The on
Exactly, to modify a pointer you need a pointer to that pointer. Remember
in C, function parameters are "read only" because they're always copies of
the calling variable's values.
This is wrong:
function abcd(void *p) {
p = malloc(sizeof(int)); // Memory leaking
*p = 1;
}
main () {
int *p
On Mon, Mar 28, 2016 at 06:30:42PM -0400, Boruch Baum wrote:
> 4.1] Was it a case of 'fat-fingerng'? I don't think so, but it's asking
> a lot to attempt to re-create this because with slow bandwidth, each
> install attempt takes a long time to get to this stage. Today's
> connection was especially
On Mon, 28 Mar 2016 13:57:08 -0300
Emiliano Marini wrote:
> char *p;
> p="01234"; /* skeezy, but makes the point */
>
> Warning! Here "p" is pointing to nowhere, you don't know which memory
> locations are writing to.
Yeah, that's why I said "skeezy". But on some of compilers, you can
actually
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