c

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...

Screen reading / mouse clicking under Linux / X Window System?

I'm learning about AI and (just for fun and practice, not profit or anything evil) I'd like to write a little bot to play a rinky-dink Flash game for me. As a Microsoft hater, I'm embarrassed to say that I know and have used the required function calls some time ago under Windows, programming in Delphi. But these days I try to do everyt...

Python to C/C++ const char question

I am extending Python with some C++ code. One of the functions I'm using has the following signature: int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict, char *format, char **kwlist, ...); (link: http://docs.python.org/release/1.5.2p2/ext/parseTupleAndKeywords.html) The parameter of inter...

Macros giving problems with dladdr()

I have implemented tracing behavior using the -finstrument-functions option of gcc and this (simplified) code: void __cyg_profile_func_enter(void *this_fn, void *call_site) { Dl_info di; if(dladdr(this_fn, &di)) printf("entered %s\n", (di.dli_sname?di_dli_sname:"<unknown>")); } This works great, except for one thing: m...

Malloc inside another function (ANSI C)

Hi I'll go straight to it. I'm working on an assignment, where I suddenly ran into trouble. I have to allocate a struct from within another function, obviously using pointers. I've been staring at this problem for hours and tried in a million different ways to solve it. This is some sample code (very simplified): ... some_struct s; pr...

How do I get Bison/YACC to not recognize a command until it parses the whole string?

I have some bison grammar: input: /* empty */ | input command ; command: builtin | external ; builtin: CD { printf("Changing to home directory...\n"); } | CD WORD { printf("Changing to directory %s\n", $2); } ; I'm wondering how I get Bison to not accept (YYACCEPT?) something as a command until...

How to get length of char**?

Quick c question: How to know the length of a char* foo[]? Thanks. ...

_REENTRANT Flag in pthreads

Hi, which compiling a multithreaded program we use gcc like below: gcc -lpthread -D_REENTRANT -o someprogram someprogram.c what exactly is the flag -D_REENTRANT doing over here? ...

How to implement dynamic binary search for search and insert operations of n element

The idea is to use multiple arrays, each of length 2^k, to store n elements, according to binary representation of n.Each array is sorted and different arrays are not ordered in any way. In the above mentioned data structure, SEARCH is carried out by a sequence of binary search on each array. INSERT is carried out by a sequence of merg...

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...

In C/C++ what's the simplest way to reverse the order of bits in a byte?

While there are multiple ways to reverse bit order in a byte, I'm curious as to what is the "simplest" for a developer to implement. And by reversing I mean: 1110 -> 0111 0010 -> 0100 This is similar to, but not a duplicate of this PHP question. ...

Warning: comparison with string literals results in unspecified behaviour

So I starting the project of writing a simplified sheel for linux in c. I am not at all proficient with c nor with Linux that's exactly the reason I decided it would be a good idea. Starting with the parser, I have already encountered some problems. The code should be straightforward that's why I didn't include any comments. I am ge...

Problem with writing a hexadecimal string

Here is my code /* gcc -c -Wall -g main.c gcc -g -lm -o main main.o */ #include <stdlib.h> #include <stdio.h> #include <string.h> void stringToHex(const char* string, char* hex) { int i = 0; for(i = 0; i < strlen(string)/2; i++) { printf("s%x", string[2*i]); //for debugging sprintf(&hex[i], "%x", string[2*i]); printf("h%x\n",...

How do I clear a Direct2D render target to fully transparent

Hi all, I'm trying to draw semi-transparent rectangles on an invisible HWND. However, clearing the window with ID2D1HwndRenderTarget::Clear just makes the entire window black, so when I draw rectangles on top, they look semi-black. If I don't Clear() and don't draw, then the window is invisible, as it should be. Clear() is the culprit ...

Are C/C++/ObjC/JS Apple's only allowed langauges for iPhone development?

According to this post on Daring Fireball a new iPhone SDK Agreement release in conjunction with the iPhone OS 4.0 announcement today specifically bans any iPhone application not implemented in C, C++ Objective-C or JavaScript. The clear impact here is to the wide array of programs written in languages other than those. Is that your rea...

How do i compile a .c file on my mac?

How do i compile a .c file on my mac? ...

Does armcc optimizes non-volatile variables with -O0 ?

int* Register = 0x00FF0000; // Address of micro-seconds timer while(*Register != 0); Should I declare *Register as volatile while using armcc compiler and -O0 optimization ? In other words: Does -O0 optimization requires qualifying that sort of variables as volatile ? (which is probably required in -O2 optimization) ...

Picking apples off a tree

I have the following problem: I am given a tree with N apples, for each apple I am given it's weight and height. I can pick apples up to a given height H, each time I pick an apple the height of every apple is increased with U. I have to find out the maximum weight of apples I can pick. 1 ≤ N ≤ 100000 0 < {H, U, apples' weight and ...

Sending data to a web site over HTTP

i have a program that receives data from a wireless device over bluetooth...i now need to do some operations in the data and then send it to the website (web server!!!) as a .csv file...i also need to authenticate the device itself from it hardware address which is also obtained in the program.i am coding this in gcc linux compiler using...

C: difference between (int)x and floor(x)?

In C, what is the difference between these two? float myF = 5.6; printf( "%i \n", (int)myF ); // gives me "5" printf( "%ld \n", floor(myF) ); // also "5"? When is one preferable over the other? ...