Programming :: C With Gcc: Are All Variables Defined Like Pointers
Sep 13, 2010
i'm practicing in very basic c programs using the gcc compiler.I found that when i create two variables let's say
Code:
int a,b and Code: a=15;
b=3;
a=b;
b--;
then a equals 2.I thought that this isn't normal in C isn't it?I haven't had the time to read the gcc documentation yet...so i think it has something to do with my compiler's default settings.I use the
Code: gcc filename.c -o filename command to compile
Are all variables defined like pointers?
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Feb 8, 2011
I am writing an expect script and I wish to use environment variables that are defined outside of the script.
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Mar 27, 2010
I wonder why arrays in the C programming language are pointers to the first element of the array, not the first element of the array itself?
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Mar 23, 2010
So the place where I'm having a problem is here:
Code:
typedef struct {
void **Mem_Chunk;
[code]...
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Jun 1, 2010
What is the difference between *ptr++ and (*ptr)++. In my opinion the terminology is all over the place so if you could give an example it would be better.
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May 23, 2010
i'm a bit stuck playing with the following class setup for glut. The actual issue is with the function pointers.Basically the following code is the opengl redbook cube example slightly modified.
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Jul 14, 2011
I need to call functions that match an input string (if input str = "func1", call func1), so I have this:
Code:
#include <stdio.h>
#include <string.h>
void function_a(void) { printf("Function A
"); }
[Code].....
In the above example, the functions take no input arguments. Can they take a different number of arguments, for example, function_a(int), function_c(int, int), function_e(int, char, int)? How can I do that?
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Apr 12, 2010
I want to know is there some more efficient way of passing a pointer to a local variable as a parameter to a function in x86 asm? Right now I have to move the base pointer to a temp register, subtract from the register and pass that, like this (assuming a local var at esp-4):
Code:
mov eax, ebp
sub eax, 4
push eax
Is there a better way?
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Feb 18, 2010
I'm trying to figure out how to code for this specific type of instance - I want to use a hash and have the key be a reference to an array, and not use the key in the standard way of it being a scalar. Basically, I have a large output that I need to process line by line, and rather have access to it as an array than a big block in a scalar. For the big block hash as a scalar I would do -
Code:
foreach $CONTROLLER (<CONTROLLER_LIST>) {
$ALL_DISKS{$CONTROLLER} = `ssh -n <commands>`;
}
Now I know I could take the scalar and split it to another array after the fact like -
Code:
@TEMP_HOLD = split (/s+/,$ALL_DISKS{$CONTROLLER});
How would I code it that I would have access to the key information as an array and not a scalar? I know it needs to be a pointer and we're going to have -> in there somewhere, but not sure how to approach it. Some of the documentaiton I've been reading about referencing I've found a little confusing so far, and trying to figure out how to use them in context of what I'm working on.
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Jul 3, 2010
I've seen all three uses:
type * pointer
type *pointer
type* pointer
Are these 3 forms essentially the same, i.e., is the spacing as used here a non-factor when declaring pointers?
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Mar 25, 2010
I am trying to find a way to pull Node Pointers out of the model, for use in other areas of the program. The solution is probably simple but I haven't had any luck finding it.
Model for a QTreeView:
Code:
class testModel : public QAbstractItemModel
{
public:
testModel();
~testModel();
[code]....
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Feb 17, 2011
I have the most strange problem ever in programming. I fork a process into a parent and a child. In every forked process i declare a pointer, malloc and define a different value for every pointer.When i printf the value and the address guess what? They both have the SAME ADDRESS but DIFFERENT values, as assigned..Here's the portion of my code:
pid = fork ();
switch (pid)
{
[code]....
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Jul 2, 2010
I following structure
typedef struct
{
[code]...
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May 26, 2011
I have a 10x2 matrix, I create said matrix and fill it one column with zeros and the other with ones, now when I print the matrix I get this:
column 1:
0,0,0,0,0,0,0,0,1,1
column 2:
1,1,1,1,1,1,1,1,1,1
The first two rows of the second column are being replaced into the last two rows of the first column, now I even checked in visual studio and it works fine there. A friend tried my code and he gets it even worse:
column 1:
0,0,0,0,1,1,1,1,1,1
column 2:
1,1,1,1,1,1,1,1,1,1
As far as I've seen it must be a problem with GCC, unfortunately I need to have this up and running in GCC no matter what.
[Code].....
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Apr 27, 2010
I can define all variables in tcl programming in a file for instance var.cfgand source the same file in my tcl script such assource var.cfgIs this possible in perl too?
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Dec 12, 2009
I converted my programming project over to autotools, which gives me a config.h file with all the cool definitions, like these ones:
Code:
/* Location of data files. */
#define DATADIR "/usr/local/share"
/* Define to the full name of this package. */
#define PACKAGE_NAME "lusus"
And naturally I think this is cool because then I can hardcore these into the binary. To my dismay, however, I discovered that the pre-processor does not do the text-substitution if the macro name is inside another quoted string.
Code:
// Prints out "/usr/local/share/lusus"
std::cout << DATADIR << "/" << PACKAGE_NAME << "
";
[code]....
This seems lame, because then this doesn't work:
Code:
CL_Image leaves_corner_tl(gc, "DATADIR/PACKAGE_NAME/img/leaves_corner_tl.png");
So, am I literally going to have to strcat DATADIR/PACKAGE with the other text every time I want to prefix DATADIR/PACKAGE_NAME onto another string?
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Apr 17, 2011
I have a Red Hat 4.9 server running python 2.3.4. However I need some of the new functions so I downloaded and installed Python 2.7.1. I wanted to use the "set" function which was not in the earlier version.
/bin/python is 2.3.4
/usr/local/bin/python is 2.7.1
I have a script running 2.3.4 which calls the 2.7.1 script however it fails because it cannot find the "set" command here is an example
Script1
#!/bin/python
import Mytest
[code]....
The error message is :
NameError: global name 'set' is not defined
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Mar 20, 2011
I've been reviewing some source code recently which contains many conditional compilation statements, and I found it hard to understand the code not knowing whether some macro is defined or not. Is there any way to test whether a macro is defined?
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Jun 17, 2011
I found an interesting screencast online about how to make gtk Pyton apps. The thing is, though, the guy was using the interactive shell. I've been trying to get his code into a script, and have been having troubles.
Here's what I got:
Code:
It spits out the error "NameError: global name 'browser' is not defined"
I know I'm doing something wrong with how I'm telling it where to find "browser" and "text", but I can't figure out how to point it to the right place.
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Jan 24, 2011
I wrote a shell script and was able to compile it using SHC. after that i copied it to the /bin folder and tried running it as a normal user, but i keep getting the error " operation not permitted killed "
I tried changing the permissions. but it doesn't work. it only works with sudo. there must be another way. otherwise it won't be linux right?
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Feb 19, 2010
I have created a file with a pre-defined size as follows:
Code:
#define FILEPATH "testfile"
#define FILESIZE 16
[code]...
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Oct 12, 2010
The first line of this struct:
Code:
struct custom_int {
typedef int big_int;
[code]...
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Apr 29, 2011
i got a sample.c which generate a linked list for sorting according to the number generated. then i want to split the sorting function into a header file. and it looks like the sort function in the header file could not access the linked list in the main. the error is dereferencing pointer to incomplete type
sample.c
Code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
[code]...
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Jun 27, 2009
I am dealing with some Linux kernel code, which define most its functions with Macros.The trouble I am having is to use those code in user space in Windows.
For example, I have a function defined like this:
#define list_for_each_entry_safe(pos, n, head, member)
for (pos = list_entry((head)->next, typeid(*pos), member),
n = list_entry(pos->member.next, typeid(*pos), member);
&pos->member != (head);
pos = n, n = list_entry(n->member.next, typeid(*n), member))
And in user space code, I call it in this way:
list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)
{
// My code to handle each element in the list
}
This is working like a charm in Linux, but I got errors in Windows:
It reminds me missing ';' after 'list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)'.
Does this kind of linux code not working in Windows at all? (Linux is in GCC C stand and VC is ANSI C) I prefer not to convert them to normal functions but keep it the way if it could be working under windows by some tricks.
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Jul 12, 2010
I'm running into a problem when I try to set a variable to an awk output in c-shell. Right now my command is Code: set STR_MSG_TYPE = `awk -F{ '/msg_type/ {print $2}' <filename> | tr -d }'/''*' ` I then run echo to see what the output is and it returns blank, however, when I run the same awk command from the command line, I get an actual output of "MT-715". Am I setting my variable incorrectly? I do something similar using the date command to set a STR_DATE variable earlier in the code and it works fine and I use the same syntax.
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Apr 26, 2010
I want to check if a MySQL db query will return an empty result - I first do this:
$query="SELECT * from <whatever" ;
$result=mysql_query($query) ;
$row=mysql_fetch_row($result) ;
Now how do I check if $row is empty or not? Will $row="" do the trick?
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Jun 13, 2011
I have a C header file which have arrays of predefined(known) structure type. But i dont have names of arrays and their size. when i include that file and compile my application, i want to know the names and sizesof those arrays.
purpose of application is to get the content of those arrays and to explain it in descriptive words instead of hex numbers.ofcourse this can be done by file pointers and reading also with out header file inclusion, but as i am working in C, once compiled, those variables are in my address space in i include header file.
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Mar 19, 2010
I was trying to make a code for passing variables by reference..here's the code:
#include<iostream>
using namespace std;
void fun(int& ,int& );
int main(){
[Code].....
invalid initialization of non-const reference of type 'int&' from a temporary of type 'int*'
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Mar 30, 2011
I am pretty new to PHP so excuse my dumbness. I've searched this up in quite a few places and cant find anything : Basically, I've made an array, within it are 3 more arrays. Their are two values in each array, 'Name' and 'Age'. Basically I am using a While statement to try and cycle through the 'age' value of my array and state whether or not the person is eligible. (I am actually just learning so I'm doing this to just test myself).
Here is my code
Code:
<?php
$people =array(
array('name' => 'Bob', 'age' => 15 ),
array('name' => 'Jhon' , 'age' => 10),
array('name' => 'Sue' , 'age' => 7));
//($value =& $people[0,1,2][age] );
Here was an attempt to try and create a reference to age, I tried it many different ways
while($age < 10) {
echo ('$name, is eligible') ; } ?>
Okay, so I tried to do this through two ways, one way I tried to create a reference to age, then evaluate it, without that line of code their would be no reference, which way is correct, why wont it work? I am using Xammp, so when I launch local host I get an undefined variable error. What To Do?
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Apr 17, 2011
My php knowledge is very poor (only worked with strings so far), and I am faced which a task that is a real challenge for me: I have a variable, that contains data of different type, in this order: byte, byte, string, string, string, string, short, byte, byte, byte, byte, byte, byte, byte, string.
Strings are of variable length. How could this data be parsed into variables of the right type, and then all converted to strings? What are the functions to use? Strings are unicode ones, and they are delimited by "
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