Userdefined function for printf
Is it possible to replace printf with userdefined function or is it possible to create function similar like printf ...
c
How to synchronize multiple proccess in c through basic signal handling
Hi, people. For a academic exercise i have to implement a program in c for nix platform which is to synchronize multiple processes through signal handling, using only signal,pause,kill and fork basic functions. I searched google and have not found any clear example: I hope the wisdom of one of you will light my way. Thanks! ...
An easy way to replace fread()'s with reading from a byte array?
I have a piece of code that needs to be run from a restricted environment that doesn't allow stdio (Flash's Alchemy compiler). The code uses standard fopen/fread functions and I need to convert it to read from a char* array. Any ideas on how to best approach this? Does a wrapper exist or some library that would help? Thanks! EDIT: I...
how to find 2 to the power of n . n ranges from 0 to 200
Assume my system as 32 bit machine. Considering this if I use long int for n>63 I will get my value as 0. How to solve it? ...
Trouble with a sequential search algorithm
Also why does this give me an error because I used bool? I need to use this sequential search algorithm, but I am not really sure how. I need to use it with an array. Can someone point me in the correct direction or something on how to use this. bool seqSearch (int list[], int last, int target, int* locn){ int looker; looker...
Write pointer to file in C
I have a stucture: typedef structure student { char *name; char *surname; int age; } Student; I need to write it to binary file. Student *s = malloc(sizeof(*s)); I fill my structure with data and then i write in to the file: fwrite(s, sizeof(*s), 1, fp); In my file doesnt exist a name and surname, it have an adresses of c...
c - difficulties with bit operations
I'm debugging a program with GDB. unsigned int example = ~0; gives me: (gdb) x/4bt example 0xffd99788: 10101000 10010111 11011001 11111111 why is this not all 1's? i defined it as ~0... then the next line of code is: example>>=(31); and GDB gives me this when I try to examine the memory at bits: (gdb) x...
How can i store data in C in a tabular format?
Hi, I want to store data in C in tabular format. I am having difficulty in relating the following. Can someone help? For example: I want to store the follwong entries, then what should be the ideal way of storing in C? IP Address Domain Name 1.) 10.1.1.2 www.yahoo.com 2.) 20.1.1.3 ...
What is "null pointer assignment error"?
One of job interview questions on C pointers here is the following: what is null pointer assignment error? I've googled for a while and don't see any reasonable explanation. What is that? Trying to write through a null pointer? Something architecture- or environment-specific? What exactly is that error? ...
Why do pthreads’ condition variable functions require a mutex?
I’m reading up on pthread.h; the condition variable related functions (like pthread_cond_wait(3)) require a mutex as an argument. Why? As far as I can tell, I’m going to be creating a mutex just to use as that argument? What is that mutex supposed to do? ...
A Strange Problem in Heap Memory!
I found one thread of a multi-threaded application to be crashing in VxWorks. I don't have debug information. On deeper analysis I found that the crash is being caused due to a global memory address value being changed. This global memory address (which is an address to a function. I am using a function pointer) is being stored at a pa...
How to check if a file descriptor has any data available?
I'd like to know if a fd has data available for reading. I have tried ioctl with FIONREAD but that results in a "Operation not supported error". Any ideas? ...
Fragmentation error while executing C program.
#include<stdio.h> struct table { char *ipAddress; char *domainName; struct table *next; }; struct table *head = NULL; void add_rec(); void show_rec(); int main() { add_rec(); show_rec(); return 0; } void add_rec() { struct table * temp = head; struct table * temp1 = (struct table *)malloc(sizeof(struct ta...
Passing a pointer to a function that doesn't match the requirements of the formal parameter
int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not matc...
FreeRTOS queues for IO before scheduler starts (or after it stops)
I'm looking for advice on how to best implement thread-safe IO (e.g. for printf going to a debug serial port) in an environment in which the operating system scheduler may yet to have started, be running, suspended or may have stopped or crashed. I'm using Newlib and FreeRTOS. At the moment, I'm doing the (seemingly-standard) FreeRTOS ...
C threads question
Write program that has two threads one is reading numbers from the user and the other is printing them such that the first thread reads a new number only after it has been printed by the second thread. Declare one global varaible to use for reading and printing. #include <stdio.h> #include <pthread.h> #include <semaphore.h> sem_t m; vo...
problem with threads
I want to be done for 10 times, to scan the number and print it again. How can I do that? #include <stdio.h> #include <pthread.h> #include <semaphore.h> sem_t m; int n; void *readnumber(void *arg) { scanf("%d",&n); sem_post(&m); } void *writenumber(void *arg) { //int x =3; //while(x>0) //{ //x ...
getnameinfo specifies socklen_t
The 2nd arg for the getnameinfo prototype asks for a socklen_t type but sizeof uses size_t. So how can I get socklen_t ? Prototype: int getnameinfo(const struct sockaddr *restrict sa, socklen_t salen, char *restrict node, socklen_t nodelen, char *restrict service, socklen_t servicelen, int flags); Example: struct socka...
C check before writing to closed pipe
Is there an easy way to check if a pipe is closed before writing to it in C? I have a child and parent process, and the parent has a pipe to write to the child. However, if the child closes the pipe and the parent tries to read - I get a broken pipe error. So how can I check to make sure I can write to the pipe, so I can handle it as an...
GCC - How to realign stack?
I try to build an application which uses pthreads and __m128 SSE type. According to GCC manual, default stack alignment is 16 bytes. In order to use __m128, the requirement is the 16-byte alignment. My target CPU supports SSE. I use a GCC compiler which doesn't support runtime stack realignment (e.g. -mstackrealign). I cannot use any ot...