pointers

C# huge size 2-dim arrays

I need to declare square matrices in C# WinForms with more than 20000 items in a row. I read about 2GB .Net object size limit in 32bit and also the same case in 64bit OS. So as I understood the single answer - is using unsafe code or separate library built withing C++ compiler. The problem for me is worth because ushort[20000,20000] is...

Accessing any structs members at run-time.

Is it possible to get access to an individual member of a struct or class without knowing the names of its member variables? I would like to do an "offsetof(struct, tyname)" without having the struct name or member variable name hard coded amoungst other things. thanks. ...

pointer in c and the c program

Hello, I am studying pointers and I encountered this program: #include <stdio.h> void swap(int *,int *); int main() { int a=10; int b=20; swap(&a,&b); printf("the value is %d and %d",a,b); return 0; } void swap(int *a,int*b) { int t; t=*a; *a=*b; *b=t; printf("%d and%d\n",*a,*b); } Can any on...

C++ Pointer trouble with File I/O

Hi, I am writing a function that takes in a output target file and a couple of other arguments. I am currently having trouble with converting types between the argument passed in and using it in the fopen_s() method. FILE* outputf; void myfunc(FILE* fin, CString finpath,...) { outputf = fopen_s(&fin, finpath, "w"); ....... } I'...

memcpy segmentation fault on linux but not os x

I'm working on implementing a log based file system for a file as a class project. I have a good amount of it working on my 64 bit OS X laptop, but when I try to run the code on the CS department's 32 bit linux machines, I get a seg fault. The API we're given allows writing DISK_SECTOR_SIZE (512) bytes at a time. Our log record consists...

From where starts the process' memory space and where does it end?

Hi, On Windows platform, I'm trying to dump memory from my application where the variables lie. Here's the function: void MyDump(const void *m, unsigned int n) { const unsigned char *p = reinterpret_cast<const unsigned char *>(m); char buffer[16]; unsigned int mod = 0; for (unsigned int i = 0; i < n; +...

C: Extrapolating type from void pointer

Say a function takes a void pointer as an argument, like so: int func(void *p); How can we determine or guess the type of what p is pointing to? ...

char pointers & integer pointers (++)

i have two pointers, char *str1; int *str2; if i look at the size of both the pointers lets assume str1=4 bytes str2=4 bytes str1++ will increment by 1 byte but if str2++ will increment 4 byte could anybody tell e the concept behind this? ...

Pointer-like behavior in Java

I got the following: class A{ int foo; } class B extends A{ public void bar(); } I got a instance of A and want to convert it to an instance of B without losing the reference to the variable foo. For example: A a = new A(); a.foo = 2; B b = a; <-- what I want to do. //use b b.foo = 3; //a.foo should now b...

How do I return the indices of a multidimensional array element in C?

Say I have a 2D array of random boolean ones and zeroes called 'lattice', and I have a 1D array called 'list' which lists the addresses of all the zeroes in the 2D array. This is how the arrays are defined: define n 100 bool lattice[n][n]; bool *list[n*n]; After filling the lattice with ones and zeroes, I store the addresses of th...

C++ design question, container of instances and pointers

Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines...

Casting pointer to object to void * in C++

I've been reading StackOverflow too much and started doubting all the code I've ever written, I keep thinking "Is that undefined behavour?" even in code that has been working for ages. So my question - Is it safe and well defined behavour to cast a pointer to an object (In this case abstract interface classes) to a void* and then later ...

C++ How do you set an array of pointers to null in an initialiser list like way?

I am aware you cannot use an initialiser list for an array. However I have heard of ways that you can set an array of pointers to NULL in a way that is similar to an initialiser list. I am not certain how this is done. I have heard that a pointer is set to NULL by default, though I do not know if this is guaranteed/ in the C++ standard...

C pointers and addresses

Hi, I always thought that *&p = p = &*p in C. I tried this code: #include <stdio.h> #include <stdlib.h> char a[] = "programming"; char *ap = &a[4]; int main(void) { printf("%x %x %x\n", ap, &*(ap), *&(ap)); /* line 13 */ printf("%x %x %x\n\n", ap+1, &*(ap+1), *&(ap+1)); /* line 14 */ } The first printf line (line 13) gi...

How can I return to a string address and then assign it to a new string?

I have 1 function that I want to return the address of an assigned string to the main function and assign an new string pointer with the same address so that the new string will have the contents of the old string. For example: unknown_datatype function() { char *old = "THE STRING"; return old; } int main() { ch...

Deleting a non-owned dynamic array through a pointer

Hello all, I'm relatively novice when it comes to C++ as I was weened on Java for much of my undergraduate curriculum (tis a shame). Memory management has been a hassle, but I've purchased a number books on ansi C and C++. I've poked around the related questions, but couldn't find one that matched this particular criteria. Maybe it's so ...

In a class with no virtual methods or superclass, is it safe to assume (address of first member variable) == this?

Hi all, I made a private API that assumes that the address of the first member-object in the class will be the same as the class's this-pointer... that way the member-object can trivially derive a pointer to the object that it is a member of, without having to store a pointer explicitly. Given that I am willing to make sure that the co...

C++ using cdb_read returns extra characters on some reads

Hi All, I am using the following function to loop through a couple of open CDB hash tables. Sometimes the value for a given key is returned along with an additional character (specifically a CTRL-P (a DLE character/0x16/0o020)). I have checked the cdb key/value pairs with a couple of different utilities and none of them show any addit...

C++ private pointer "leaking"?

I'm going to create a class to hold a long list of parameters that will be passed to a function. Let's use this shorter example: class ParamList{ public: ParamList(string& a_string); string& getString(); //returns my_string private: string& my_string; } My question is this: my_string is private, yet I'm returning the ref...

list of pointers in c++

What i want to do is for (list<cPacket *>::iterator i = cache.begin(); i != cache.end(); i++){ if( strcmp(i->getName(),id) == 0 ){ return true; } } where getName is function of the class cPacket, But it does not work, i tries also i.operator->()->getName(), and again nothing. Can anybody help me? ...