These are my C codes simply print “Hello" Message. And I want to make mylib.c as shared library.
[mylib.c]
#include <stdio.h>
int mylib();
int main(){
mylib();
return 0;
}
int mylib(){
printf("### Hello I am mylib #####\n");
return 0;
}
[drive.c]
#include <stdio.h>
int mylib();
int main(){
mylib();
return 0;
}
At the firest I compiled mylib.c with folowing command line to make mylib.o
gcc –fPIC –g –c –Wall mylib.c
Then tried to make it shared librarly like this
gcc -shared -Wl,-soname,libmylib.so.1 -o /opt/lib/libmylib.so.1.0.1 mylib.o -lc
And I did ldconfig to update /etc/ld.so.cache
Finaly I compiled drive.c link with mylib but linker showed error
gcc -g -Wall -Wextra -pedantic -I./ -L./ -o drive drive.c –lmylib
/usr/bin/ld: cannot find –lmylib
Dose someone tell me how can I compile it?
In my way, you have to follow some ways to use shared library in C.
At first I have created a header file named "shared_library.h", in this file I have introduced a function named "method" as a function of this library.
The code is following:
/*-------This is starting of shared_library.h file-----------*/
void method();
/*-------------This is ending of shared_library.h file--------*/
Then I have defined the method in another file named "shared_library.c". The definition as in code is:
/*-------------This is starting of shared_library.c file---------*/
#include "shared_library.h"
void method()
{
printf("Method is called");
}
/*-------------This is ending of shared_library.c file---------*/
And finally, the header "shared_library.h" is ready to use. I use the library in my main C file named "main.c". The contents of "main.c" are as follows:
/*-------------This is starting of main.c file----------------*/
#include <stdio.h>
#include "shared_library.h"
int main()
{
method();
return 0;
}
/*-------------This is ending of main.c file----------------\*/
I found this article ld cannot find an existing library.
It works if I change to gcc -g -Wall -Wextra -pedantic -I./ -L/opt/lib -o drive drive.c –l:libmylib.so.1
Related
I am trying to link guile to an Rcpp file. It seems like things compile but there is an error when loading:
sourceCpp("test_2.cpp", rebuild = TRUE, showOutput = TRUE)
/usr/lib/R/bin/R CMD SHLIB --preclean -o 'sourceCpp_2.so' 'test_2.cpp'
g++-10 -I"/usr/share/R/include" -DNDEBUG -I"/home/matias/R/x86_64-pc-linux-gnu-library/4.0/Rcpp/include" -I"/home/matias/Documentos/Program/R/guile" -fpic -O3 -march=native -mtune=native -fPIC -pthread -I"/usr/include/guile/3.0" -c test_2.cpp -o test_2.o
g++-10 -shared -L/usr/lib/R/lib -lm -ldl -lgmpxx -lgmp -lmpfr -lmpc -lguile-3.0 -lgc -o sourceCpp_2.so test_2.o -L/usr/lib/R/lib -lR
Error in dyn.load("/tmp/Rtmpm2flY8/sourceCpp-x86_64-pc-linux-gnu-1.0.5/sourcecpp_29e2d33505085/sourceCpp_2.so") :
unable to load shared object '/tmp/Rtmpm2flY8/sourceCpp-x86_64-pc-linux-gnu-1.0.5/sourcecpp_29e2d33505085/sourceCpp_2.so':
/tmp/Rtmpm2flY8/sourceCpp-x86_64-pc-linux-gnu-1.0.5/sourcecpp_29e2d33505085/sourceCpp_2.so: undefined symbol: scm_init_guile
The linking works fine if I remove the Rcpp header and build directly with g++ instead.
My Makevars look like this:
CXX = g++-10
CXXFLAGS = -O3 -march=native -mtune=native -fPIC -pthread -I"/usr/include/guile/3.0"
CXXSTD = -std=c++11
LDFLAGS = -lm -ldl -lgmpxx -lgmp -lmpfr -lmpc -lguile-3.0 -lgc
The .cpp file:
#include <Rcpp.h>
#include <stdio.h>
#include <libguile.h>
using namespace Rcpp;
// [[Rcpp::export]]
int test_guile() {
SCM func, func2;
scm_init_guile();
scm_c_primitive_load("script.scm");
func = scm_variable_ref(scm_c_lookup("simple-func"));
func2 = scm_variable_ref(scm_c_lookup("quick-test"));
scm_call_0(func);
scm_call_0(func2);
return 0;
}
You are so, so close. You essentially solved this. I just took your file, made a small modification of making the script an argument and (as you didn't post script.scm) commented out the content-specific stuff. We still load it though:
#include <Rcpp.h>
#include <stdio.h>
#include <libguile.h>
using namespace Rcpp;
// [[Rcpp::export]]
int test_guile(std::string file) {
SCM func, func2;
scm_init_guile();
scm_c_primitive_load(file.c_str());
//func = scm_variable_ref(scm_c_lookup("simple-func"));
//func2 = scm_variable_ref(scm_c_lookup("quick-test"));
//scm_call_0(func);
//scm_call_0(func2);
return 0;
}
Similarly I just added a src/Makevars to the Rcpp.package.skeleton() created file. This is not good enough to ship as you need some minimal configure or alike logic to get these values from guile-config-3.0 or alike. But it passes the litmus test. C++11 is the default already under R 4.0.*, and the compiler is recent on my box anyway so we just have this (after removing a few GNU GMP and related parts we do not need):
PKG_CXXFLAGS = -I"/usr/include/guile/3.0"
PKG_LIBS = -lguile-3.0 -lgc
This now builds, installs, and runs just fine:
> file <- system.file("guile", "script.scm", package="RcppGuile")
> RcppGuile::test_guile(file)
[1] 0
>
For reference, I committed and pushed the entire example package here. If you provide a pointer to script.scm we can add that too.
Edit: A few seconds of googling leads to the script.scm you may have used so now we have a fully working example with a working embedded Guile interpreter:
> library(RcppGuile)
> test_guile(system.file("guile", "script.scm", package="RcppGuile"))
Script called, now I can change this
Adding another function, can modify without recompilation
Called this, without recompiling the C code
[1] 0
>
I want to define an inline function in a header file (.h) which can be included by numerous source files (.c). Here is a minimal example with 1 header and 2 source files:
Header file foo.h
int ifunc(int i);
extern inline
int
ifunc(int i)
{
return i + 1;
}
Source code file: foo.c
#include <stdio.h>
#include "foo.h"
int foo2(int i);
int main()
{
printf("%d\n", foo2(1));
return 0;
}
Source code file foo2.c
#include "foo.h"
int foo2(int i)
{
return ifunc(i);
}
The problem
When I compile with optimization,
gcc -g -Wall -O2 -o foo foo.c foo2.c
$ ./foo
2
everything works fine. However when I turn off optimization, I get this error:
gcc -g -Wall -o foo foo.c foo2.c
/tmp/cc3OrhO9.o: In function `foo2':
foo2.c:5: undefined reference to `ifunc'
Can someone please explain how to fix so that I can run the code with and without -O2? I am using gcc 4.8.5.
if you replace foo.h with
static inline int ifunc(int i)
{
return i + 1;
}
Both will work.
Declaring it extern means it'll be defined somewhere else which in your original example does not happen. And the optimized build doesn't flag as an error because it already optimized it to be inline it but the non-optimized build does not find a definition in any of the .o files (since they were all compiled with ifunc being an extern as defined in foo.h).
Declaring as static inline will ensure that it is local to each file (the downside being that if it does not inline it, you'll end up with each .o that needs it having a local copy, so don't overdo it).
This seems a simple but somehow the compile sends this error message which I'm not able understand thus correct my code.
This is a simplified version of what I did, just so it can appear the error for you:
Main.cpp
include "myfunction.h"
int main(){
std::vector<int> myVet = {1,4,3};
sequence(1,2,1,myVet);
}
myfunction.h
#include <vector>
/*funtion creates a sequence*/
void sequence(int start, int end,
int step, std::vector<int> skip);
myfunction.cpp
#include "myfunction.h"
void sequence(int start, int end,
int step, std::vector<int> skip){
auto x = 0;
};
This gives me an error message which says
In function 'main':
/home/machina/Documents/Grafos&Redes/Implementação/main.cpp:18: undefined reference to 'sequence(int, int, int, std::vector <int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status
Could you please explain me why it appears?
This is the following command which I've been using for compiling
g++ -std=c++11 -g -Wall -Wextra -Werror main.cpp -o main.out
You are only passing main.cpp to g++.
g++ needs to know about myfunction.cpp where your function is defined so as to compile and link it to your program.
The command to use should be:
g++ -std=c++11 -g -Wall -Wextra -Werror main.cpp myfunction.cpp -o main.out
How to compile this code?
/* main.c file*/
#include <stdio.h>
int main(void)
{
int c;
c = add(5,5);
printf("sum is %d\n",c);
return 0;
}
Add.c(in same directory)
/*add.c*/
int add(int a, int b)
{
int c;
c = a + b;
return c;
}
Add.h(in same directory)
/* add.h file*/
int add(int, int);
Then i am create a object file for add.c
$ gcc -c -Wall add.c -I.
Then i am try to create a object file for main.c
$ gcc -c -Wall main.c -I.
main.c:6:2: warning: implicit declaration of function ‘add’ [-Wimplicit-function-declaration]
c = add(5, 5);
^
Please any one tell, how to give the headfile name in compiling time.
you can either use #include "Add.h" at the top of your main.c (this is the preferred route), or you can use the -include command line flag (this is discouraged because it does not scale and is not portable):
gcc -c -Wall main.c -I. -include Add.h
I have my Main C++ Class main.cpp...
#include "fs.h"
int main(void)
{
return minit();
}
The fs.h:
#ifndef __FS__
#define __FS__
int minit (void);
#endif
And a fs.o (with minit() into) file that is already an object file, compiled with g++ without -g.
Here is my makefile:
myfs: main.o fs.o
g++ -o myfs -m32 -Wall fs.o main.o
main.o: main.cpp fs.h
g++ -o main.o -m32 main.cpp
Every time I try to link everything, the linker says that in main.cpp there is a undefined reference to minit(); What could it be?
You have defined a function called minit() within actually IMPLEMENTING it - that is why you are having this problem.
You need to actually write the function minit():
int minit(void) {
return 0;
}
For example...
You should point it to compiler that the function is defined elsewhere. Try changing this declaration:
int minit (void);
to this
extern int minit (void);