Assignment and comparison
Looking at the code: int i = 5; if (i = 0) { printf ("Got here\n"); } What does the C standard have to say about what will get printed? Or in more general terms does the assignment happen first or the comparison? ...
c
how to reduce the waiting time for connection ?
simple script for connect server: #include "hiredis.h" int main(void) { int fd; unsigned int j; redisReply *reply; reply = redisConnect(&fd, "test.com", 6379); if (reply != NULL) { printf("Connection error: %s", reply->reply); exit(1); } reply = redisCommand(fd,"PING"); printf("PONG: %s...
Function pointers in C
The following code (a function prototype): void parse_ini(FSFILE *fp, void(*secFunc)(char*), void(*varFunc)(char*, char*)); presents errors when compiled: util\setup.c:38: error: syntax error before '*' token util\setup.c:38: error: 'parse_ini' declared as function returning a function util\setup.c:38: error: syntax error before 'voi...
right way to define pointer to the function
hello, everyone, I have this piece of the code: void foo(int var, int var1) { printf("%d\n", var); printf("%d\n", var1); } void foo_for_foo( void (*some_function)(int, int)) { int x = 5; some_function(x, x); } int main() { void (*ptr_foo); // <- look here ptr_foo = &foo; foo_for_foo(ptr_foo); return 0; } does it matter how...
Pointer Question
Hi, Can you please explain to me what is happening here? char data[128]; // Create char array of size 128. long * ptr; // Create a pointer. ptr = (long *) data; // ?? Mainly, what does the (long *) mean? Does it mean that the data is of type char, and I am casting the reference to data as a reference to a long? Thank you. ...
Why are no strict-aliasing warnings generated for this code?
I have the following code: struct A { short b; }; struct B { double a; }; void foo (struct B* src) { struct B* b = src; struct A* a = (struct A*)src; b->a = sin(rand()); if(a->b == rand()) { printf("Where are you strict aliasing warnings?\n"); } } I'm compiling the code with the following c...
Linking in C using gcc
If I wanted to link the following objects and libraries, p.o → libx.a → p.o Where a → b denotes that b defines a symbol that is referenced by a. Would UNIX% gcc p.o libx.a be enough in the command line or do I need to do something like: UNIX% gcc p.o libx.a p.o Thanks. ...
Plugin System without rebuilding for each OS?
I'm making a game that will allow content development and I'd like it to be sort of a DLL based system. But, my game works for Linux (X86 arch) , Mac OSX and 32 bit Windows. Is there a way I could allow content developers to compile only one thing and have it work based on the platform? I fear it might get confusing if there are 3 versio...
how to get error code from sqlite3_exec
I have an update that is failing due to a constraint on the table, but sqlite3_exec only returns an error code of 1 instead of 19. How do I get the correct error code? ...
Newbie cant see why code is erroring, but knows where it is erroring
I have a problem with my code, good news is I actually pinpointed the problem, bad news is I do not understand why it is a problem. Also should this be return or exit? This is my getNums() function,...so far. first my code calls getLine() which gets the line and returns its character length. Then get nums is given, the line, length o...
Building an USB peripherial
I would like to control an RC model via USB from my computer. I don't need a real radio control, so controlling the servos directly through cables is sufficitent (yes, there will be cables between the model and the controlling unit). I thought I would build some microcontroller-based device which would be connected to the computer via US...
How to check C source code against the current standard?
I'm continuing to learn C and would like to adhere to whatever is the current standard, but finding a good reference to that seems to be problem. From what I've found online (mostly through Google and Wikipedia) is that the current standard used today is C99, more formally the ISO/IEC 9899:1999 standard. When I'm writing C code, I ofte...
trying to store an array of pointers
struct match { char men[64]; char women[64]; char menNum[1000]; char woNum[1000]; }; void printOut(); int matchMaking(struct match* p, struct match* q, int k); int main(void) { FILE* fin; FILE* fout; fin = fopen("input.txt", "r"); fout = fopen("out.txt", "w"); int matchNum = 0; int size; int i...
Are there any c demos with netfilter?
I want to forward packets by netfilter, so I want to get some c demos to get start, thanks ...
how does a system ensure coherence between memory and cache
For example if I write to a particular memory location (ex: DMA transfer) how does it get affected in my cache? ...
How to use OpenGL and GLUT in Cygwin
I've attempted to follow the instructions from various places [1][2][3], but I keep getting link errors when attempting to use GLUT and OpenGL in Cygwin. Everything I try gives me a link error similar to: $g++ -Wall -pedantic -c -o triangle.o triangle.cpp $g++ -o triangle *.o -lglut32 -lglu32 -lopengl32 -o triangle triangle.o:triangle....
c programming query regarding sizeof operator Please specifythe output with reason in windows and linux
void main() { char c='0'; printf("%d %d",sizeof(c),sizeof('0')); } ...
Check whether a point(lat/long) is within a circle(Centre lat/long known)
Hi..I am trying to see if a given pair of (lat,long) will fall within a circular region. The centre of the circle is known (lat,long values) as well as the radius. The approcah I have used is: Calculate the distance between the centre and the given lat/long using Haversines formula. Formula: a = ( sin(delta_lat/2) )^2 + cos (vp_Curr...
Error runing OPTIMAL algoritm
Any help please, a week without geting the problem **C:>pager_OPTIMAL test 100 File used fifo-test, resident set size 200 Error restoring the reference stream position Error was:: Invalid argument*/* pt_entry pte[MAX_PAGE]; /* page table */ int mem_size; /* physical memory size in page frames */ list free_l...
How to detect encodings on signed integers in C?
The ISO C standard allows three encoding methods for signed integers: two's complement, one's complement and sign/magnitude. What's an efficient or good way to detect the encoding at runtime (or some other time if there's a better solution)? I want to know this so I can optimise a bignum library for the different possibilities. I plan ...