I've been trying to compile this simple code for absolute ages but with no luck.
#include "highgui.h"
#include "opencv2/highgui/highgui_c.h"
int main()
{
int cvNamedWindow(const char* name,int flags = CV_WINDOW_AUTOSIZE);
{
cvNamedWindow("sample");
}
cvDestroyWindow("sample");
}
I am using Ubuntu 12.04 platform. At first I was getting errors saying that
highgui.h was not found.
I have now corrected that but now I am getting new ones. The compile instruction I am using is:
gcc -o window window.c -I/usr/include/opencv/
The new error is:
window.c:8:48: error: expected ‘;’, ‘,’ or ‘)’ before ‘=’ token
window.c:10:6: error: too few arguments to function ‘cvNamedWindow’
Now I'm not even sure what the problem is anymore. There doesn't seem to be any clear explanation on compilation in OpenCV. Please somebody help cos I really need to get a move on with this, can't be spending all day trying to just compile! Thanks
Try compiling this:
#include "highgui.h"
#include "opencv2/highgui/highgui_c.h"
int main() {
cvNamedWindow("sample");
cvDestroyWindow("sample");
return 0;
}
There is no default arguments in C.
You should call cvNamedWindow() as follows:
cvNamedWindow("sample", CV_WINDOW_AUTOSIZE);
Full code:
#include "highgui.h"
#include "opencv2/highgui/highgui_c.h"
int main() {
cvNamedWindow("sample",CV_WINDOW_AUTOSIZE);
cvDestroyWindow("sample");
return 0;
}
Related
I know this is a weird question, but I want to get the "initscr" function error mentioned by the doc (getting invalid pointer and an error message on stderr) to test if a wrapper works properly.
But I don't find any information about that. I'm currently working with ncurses 6.2.
After few research, I have found that the invalid pointer is really a NULL, not just an empty one pointing on anywhere.
But I'm not able to break the function...
If someone know how to help me to break down this, feel free to leave a comment.
The following program:
#include <curses.h>
#include <malloc.h>
#include <stdlib.h>
bool my_malloc_disabled;
void *malloc(size_t size) {
if (my_malloc_disabled) {
return NULL;
}
void *__libc_malloc(size_t);
return __libc_malloc(size);
}
int main() {
my_malloc_disabled = 1;
initscr();
}
does:
$ gcc file.c -lcurses
$ ./a.out
Error opening allocating $TERM.
Here's the code I wrote.
#include <stdlib.h>
#include <stdio.h>
int main(void){
printf("hello World.");
return 0;
}
This is the error message
Execution of '"C:\Users\Happy Birthday\Desktop\Coding\C++\C_C++ project\simple program.exe"' in 'C:\Users\Happy Birthday\Desktop\Coding\C++\C_C++ project' failed.|
I figured it out. I had to go to the location of the bin for MinGW, copy and paste its address into the Toolchain executables tab of the global compiler settings, as opposed to auto detecting it.
#include <stdio.h>
#include <math.h>
int exp_for_level(int n) {
return (int)(100 * pow(n, 2.3));
}
int main(){
int x;
x = exp_for_level(6);
printf("%d", x);
return 0;
}
I receive the following error when I run this code on an online compiler
/tmp/cc28S7ML.o: In function exp_for_level':
main.c:(.text+0x19): undefined reference to `pow'
collect2: error: ld returned 1 exit status
How do I rectify this?
After I couldn't get it to work on the online compiler, I followed advice from some other threads on
The file is stored under a file grades.c on my mac
I've tried entering this
$ gcc - Wall - lm -o grades grade . c
into my terminal and i just get zsh error: command not found
Any ideas on what the issue is here too?
The online compiler I'm using is
https://www.tutorialspoint.com/compile_c_online.php
EDIT: in my post, in main I'd miswritten the function as exp_to_level instead of exp_for_level. Didn't copy paste the entire code as it's too long. I narrowed it down and retyped it to the portion that yields the error.
There are some errors in your code, you have defined a function exp_for_level but you use exp_to_level.
Then your x variable is not defined
If you fix your code like this:
#include <stdio.h>
#include <math.h>
int exp_for_level(int n) {
return (int)(100 * pow(n, 2.3));
}
int main(){
int x = exp_for_level(6);
printf("%d", x);
return 0;
}
and you compile:
gcc -Wall powtest.c -o powtest -lm
it works.
About the error on the online compiler:
The undefined reference error occurs because you are missing -lm linker option.
Edit the online compiler command clicking on Project->Compile Options:
About this problem on your local machine:
After I couldn't get it to work on the online compiler, I followed
advice from some other threads on The file is stored under a file
grades.c on my mac I've tried entering this
$ gcc - Wall - lm -o grades grade . c
into my terminal and i just get zsh error: command not found
you don't have the compiler installed.
You should install clang, Have a look to this question
First of all your function name is wrong in the main take a look here exp_for_level
and in main its exp_to_level change one of them then also add int x in main to solve the issue.
I'm trying to use InetPtonW:
if(InetPtonW(AF_INET, argv[1], &ThisSenderInfo.sin_addr)<=0) {
return 1;
}
However I get the following message when compiling:
warning: implicit declaration of function 'InetPtonW' [-Wimplicit-function-declaration]
undefined reference to `InetPtonW'
collect2.exe: error: ld returned 1 exit status
I've read the documentation located here and I've followed everything but still can't get it to work.
• I'm compiling with Ws2_32 library gcc test.c -o test -lws2_32 using MinGW
• I've included the needed header files #include <ws2tcpip.h> and #include <windows.h>
• I've tried using InetPton but it returns the same error
• Running on Windows 10
I recall running into this exact issue some many months ago. #alk's comment points to a question whose accepted answer feels very similar to what fixed it for me.
You should be able to #define a version macro (or two) before your #include lines to fix it.
While I feel strongly that the aforementioned answer is correct, I'll update this answer later today when I can verify.
Update!
The code I was referencing above doesn't have InetPtonW in it anymore but it had the necessary #defines in it. Here's a brief example that compiles on my machine (win10/mingw64/gcc 8.2.0):
Z:\Some\Directory>gcc test.c -o test -lmswsock -lws2_32
#define NTDDI_VERSION NTDDI_VISTA
#define WINVER _WIN32_WINNT_VISTA
#define _WIN32_WINNT _WIN32_WINNT_VISTA
#include <winsock2.h>
#include <Ws2tcpip.h>
#include <stdio.h>
/* This is "test.c", please pardon the lack of error checking. */
int main(void) {
BYTE ipbuf[4] = {0};
WSADATA wsa;
WSAStartup(MAKEWORD(2,2), &wsa);
printf("%d: ", InetPtonW(AF_INET, L"127.0.0.1", &ipbuf));
for(int i = 0; i < 4; ++i)
printf("%hhu.", ipbuf[i]);
WSACleanup();
}
Output should look like:
Z:\Some\Directory>gcc test.c -o test -lmswsock -lws2_32
Z:\Some\Directory>test
1: 127.0.0.1.
Z:\Some\Directory>
It's a linking error. which say that, included library path, the given function not found. please make sure your dll library path for InetPtonW or make sure that is available in your system or not.
I have recently started learning C as a side project. I am working under OpenSuse with the latest NetBeans using the GCC as toolset for compiling.
One of the very first programs that I made was this:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/*
*
*/
int main(int argc, char** argv) {
double rad = 1;
double result = 0;
result = sin(rad);
return (EXIT_SUCCESS);
}
This is a simple, no-brainer example that should have worked without a problem. However, I get a Build Error: Exit code 2(error in line 18, undefined reference to sin) when trying to compile.
Interestingly enough, if I remove the assignment of the value of sin(rad) to result OR replace rad with a hard coded value, the program compiles just fine.
What am I doing wrong here?
In C, you need to link to the math library:
Add this to the command line options:
-lm
Be sure that your are linking with the math library.
$ gcc myprog.c -lm