When I compile this code, I get the following gcc errors:
/tmp/ccUigsI6.o: In function `main':
/home/matt/Dropbox/school/2011/cs3210/test/sizeterm.c:9: undefined reference to `setupterm'
/home/matt/Dropbox/school/2011/cs3210/test/sizeterm.c:10: undefined reference to `tigetnum'
/home/matt/Dropbox/school/2011/cs3210/test/sizeterm.c:11: undefined reference to `tigetnum'
collect2: ld returned 1 exit status
make: *** [sizeterm] Error 1
Here's the code:
#include <stdio.h>
#include <term.h>
#include <curses.h>
#include <stdlib.h>
int main()
{
int nrows, ncolumns;
setupterm(NULL, fileno(stdout), (int *)0);
nrows = tigetnum("lines");
ncolumns = tigetnum("cols");
printf("This terminal has %d columns and %d rows\n", ncolumns, nrows);
exit(0);
}
Libncurses is installed correctly on my machine. I get the same results from my Arch linux laptop, and the Ubuntu server installed at my school. This particular piece of code is taken directly out of the book. Am I doing something wrong? I've done some googling and it looks as though people have had this problem before, but I can't narrow down a solution.
You forgot to actually link against ncurses. Add -lcurses to the gcc command line.
This is exactly what you find in the same book as where you found this code:
$ cc -o badterm badterm.c -lncurses
Beginning linux programming 4th edition, chapter 5: Terminals, page 196.
Related
EDIT My problem is solved Thanks all very much
the problem was that I only included cs50.h but didn't include cs50.c and that the library I had was an old one containing only GetInt but not get_int
when I downloaded the new library everything worked
I'm taking CS50x course and I want to use get_int function which is included in cs50 library on VS code ...
I downloaded cs50 library and copied cs50.h and cs50.c to d:\MinGW\bin
my code is
#include <stdio.h>
#include <cs50.h>
int main(void)
{
int age = get_int("Age?");
int days=age*365;
printf("Your age is %i which means that you are %i days old", age, days);
}
when I try to compile it using
gcc 0.c -o 0
it writes
0.c: In function 'main':
0.c:7:15: warning: implicit declaration of
function 'get_int' [-Wimplicit-function-declaration]
7 | int age = get_int("Age?");
| ^~~~~~~
d:/mingw/bin/../lib/gcc/x86_64-w64-mingw32/9.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\AbdoMAD\AppData\Local\Temp\ccTefKbe.o:0.c:(.text+0x15): undefined reference to `get_int'
collect2.exe: error: ld returned 1 exit status
the auto complete of vs code doesn't have get_int but it has GetInt
But when I use it and the code is
#include <stdio.h>
#include <cs50.h>
int main(void)
{
printf("Age?")
int age = GetInt();
int days=age*365;
printf("Your age is %i which means that you are %i days old", age, days);
}
it returns
d:/mingw/bin/../lib/gcc/x86_64-w64-mingw32/9.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\AbdoMAD\AppData\Local\Temp\cc3NVsiz.o:1.c:(.text+0x1a): undefined reference to `GetInt'
collect2.exe: error: ld returned 1 exit status
What should I do to use get_int or at least GetInt in VS code??
If you want get_int, don't write it GetInt.
If you use https://sandbox.cs50.io, you can do:
gcc 0.c -lcs50 -o 0
and you first code will work.
To get more information, try googling "c link to library".
#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 set a function pointer to point to the pow function.
Here's my code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main(void){
double (*func)(double, double) = pow;
return 0;
}
But the program doesn't compile.
I get this error:
$ gcc test.c -o test
/tmp/ccD6Pmmn.o: In function `main':
test.c:(.text+0x8): undefined reference to `pow'
collect2: error: ld returned 1 exit status
I'm using Ubuntu 15.10.
Anyone knows what's wrong with my code?
Thanks
You need to compile with -lm via command line or configure your IDE to add it into the linking process. This is due to the fact that some libraries are pretty large and to avoid taking up space in your program and compilation time, this was setup at the beginning of C when computers were much slower and would take MUCH more to compile and a matter of space was CRUCIAL.
I want write simple C program to set ACL to one particular file on Linux. My starting code is trying to use function from "acl.h". I'm using Ubuntu 13.10, I've installed "Access control list utilities" - "acl 2.2.52-1". Here is my code:
#include <sys/acl.h>
#include <stdio.h>
int main () {
acl_t aclvar;
int count = 1;
aclvar = acl_init(count);
return 0;
}
The problem is, that I get error while compiling with "gcc myAcl.c" or "gcc -lacl myAcl.c":
/tmp/cc5sVzSR.o: In function `main':
myAcl.c:(.text+0x15): undefined reference to `acl_init'
collect2: error: ld returned 1 exit status
How can I resolve this error?
The libraries you link to needs to come last
gcc myAcl.c -lacl
I was testing the cblas ddot, and the code I used is from the link and I fixed it as
#include <stdio.h>
#include <stdlib.h>
#include <cblas.h>
int main()
{
double m[10],n[10];
int i;
int result;
printf("Enter the elements into first vector.\n");
for(i=0;i<10;i++)
scanf("%lf",&m[i]);
printf("Enter the elements into second vector.\n");
for(i=0;i<10;i++)
scanf("%lf",&n[i]);
result = cblas_ddot(10, m, 1, n, 1);
printf("The result is %d\n",result);
return 0;
}
Then when I compiled it, it turned out to be:
/tmp/ccJIpqKH.o: In function `main':
test.c:(.text+0xbc): undefined reference to `cblas_ddot'
collect2: ld returned 1 exit status
I checked the cblas file in /usr/include/cblas.h, and noticed there is
double cblas_ddot(const int N, const double *X, const int incX,
const double *Y, const int incY);
I don't know where it is going wrong. Why does the compiler said the "cblas_ddot" is undefined reference?
You can't just include the header - that only tells the compiler that the functions exist somewhere. You need to tell the linker to link against the cblas library.
Assuming you have a libcblas.a file, you can tell GCC about it with -lcblas.
The web site for GNU Scientific Library tells you how to do this:
2.2 Compiling and Linking
My problem was just solved. The reason is that I made a mistake when inputed the link path. Thanks for Jonathon Reinhart's answers, they are really helpful when learning how to code in linux.
The compile commands are:
gcc -c test.c
gcc -L/usr/lib64 test.o -lgsl -lgslcblas -lm
Where "/usr/lib64" is the correct link path.