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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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
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
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
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
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;
>
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:
...
> 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
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
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:
[...]
> 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 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
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
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
27 matches
Mail list logo
