Assuming this program: #include <stdio.h> #include <string.h> static void ring_pool_alloc(void **p, size_t n) { static unsigned char pool[256], i = 0; *p = &pool[i]; i += n; } int main(void) { char *str; ring_pool_alloc(&str, 7); strcpy(str, "foobar"); printf("%s\n", str); return 0; } ... is it pos...
I inherited a big application that was originally written in C (but in the mean time a lot of C++ was also added to it). Because of historical reasons, the application contains a lot of void-pointers. Before you start to choke, let me explain why this was done. The application contains many different data structures, but they are stor...
After perusing the web and messing around myself, I can't seem to convert a void*'s target (which is a string) to a std::string. I've tried using sprintf(buffer, "%p", *((int *)point)); as recommended by this page to get to a C string, but to no avail. And sadly, yes, I have to use a void*, as that's what SDL uses in their USEREVENT stru...
So I need to read flags in bits and set flags in bits. These bits are in various sizes of integer: int16, int32, int64, etc. I would like to have a function that does something like this: static integertype function(integertype data, char startbit, char endbit); I don't want to code what will be the same code to isolate bits from for...
Hi experts, Here is the context of the code: void THREAD_CC server_thread(void *arg) { BIO *client = (BIO *)arg; ... } Does the expression (BIO *)arg transform the void pointer arg into a pointer that points to BIO? I'm not sure if I got this right or not. Any help would be much appreciated! Z.Zen ...
Hi, I am a C/C++ programmer, but I was asked to update a program that was written in C# to communicate with a device. My knowledge of C# is very basic. The previous version was totally written in C#, but now the API that in fact access the device was changed to C. I found out that I can import the C function APIs by using: [DllImport(...
I have code that looks like this: extern "C" __declspec(dllexport) myInterface(int id, void** pFunction) { ... } I need to make the void** pFunction argument point to a function so that the caller can use this function via the pFunction pointer. This function gets called through a DLL, I don't want to do it this way but for a lot ...
Error 1 error C2036: 'const void *' : unknown size file.cpp 111 I don't follow. GCC never complains about void * pointer arithmetic, even on -ansi -pedantic -Wall. What's the problem? Here's the code- struct MyStruct { const void *buf; // Pointer to buffer const void *bufpos; // Pointer to current posi...
I've seen a lot of the following in older C code: type_t *x = (type_t *) malloc(...); What's the point of casting the pointer returned from malloc() since it's void *? Is it because older C compilers didn't support void pointers and malloc() used to return char * instead? ...
#include<iostream> #include<conio.h> using namespace std; int main() { int x = 65; int *ptr = &x; char * a= (char *)ptr; cout<<(int)*(a); getch();return 0; } Sixeof(ptr) and Sizeof(a) display 4 Sizeof(int) displays 4 and sizeof(char) displays 1 So 65 is stored in 4 byte...
Hi folks, I fall in some problem. I need to write some function like memcpy(void*, const void*), which its signature should be: void arrayCopy(void *dest, int dIndex, const void *src, int sIndex, int len) I noticed that, in many implementation of memcpy, we cast void* to char*, but I think this is not the case of me, as the arrayCop...
Ok, this compiles fine in GCC under Linux. char * _v3_get_msg_string(void *offset, uint16_t *len) {/*{{{*/ char *s; memcpy(len, offset, 2); *len = ntohs(*len); s = malloc(*len+1); memset(s, 0, *len+1); memcpy(s, offset+2, *len); s[*len] = '\0'; *len+=2; return s; }/*}}}*/ However, I'm having a prob...
I have an array in C++: Player ** playerArray; which is initialized in the constructor of the class it is in. In the destructor I have: delete playerArray; except when testing the program through Valgrind it says that there are some calls to delete to a void pointer: operator delete(void*) I want to test whether the playerArr...
In C, it's not an error to cast pointers to and from void *. A major obstacle in porting to C++ is the need to cast pointers when returning from functions dealing with generic pointers such as malloc, and functions declared in my own code such as void *block_get(Blkno const blkno);. My code however is intended to be compiled by C and C...
why is sizeof void pointer 2 ? ...
In an earlier question, I asked about typecasting pointers, but was directed to the better solution of using the C++ allocation system instead of mallocs. (I am converting some C code to C++) However, I still have an issue with a similar function: I changed: tmp = malloc(sizeof(char*) * mtmp); --> tmp = new char*[mtmp]; and free(tm...
I want to take some fields from packet struct using pointer arithmetic.But what is wrong with the code below ? In first condition i think if i go 4 byte(2 short field) from beginning of packet i get tLow .But it does not give expected value.Additionally second case i want to get data field by going 12 byte from beginning of packet .What ...
Hello I'm having problems getting this to work, class A { public: A(int n) { a = n; } int getA() { return a; } private: int a; }; int main(){ A* a[3]; A* b[3]; for (int i = 0; i < 3; ++i) { a[i] = new A(i + 1); } void * pointer = a; b = (A* [])pointer; // DOESNT...
I am trying to understand what this means, the code I am looking at has in .h typedef void (*MCB)(); static MCB m_process; in .C MCB Modes::m_process = NULL; And sometimes when I do m_process(); I get segmentations fault, it's probably because the memory was freed, how can I debug when it gets freed? I hope my questions ar...
is this valid void *p = &X; /* some thing */ p += 12; and if so what does p now point to? I have (third party) code that does this (and compiles cleanly) and my guess is that the void * was treated as a char *. My trusty K&R is silent(ish) on the topic EDIT: My little test app runs fine on gcc 4.1.1 and treats void * as char *. But ...