WHen I compile this code, it shows me linker error
#include <curses.h>
#include <ncurses.h>
int main()
{ int ch;
raw(); /* Line buffering disabled */
}
Compiler error:
/tmp/ccY9Bug1.o: In function `main':
raw.c:(.text+0x12): undefined reference to `raw'
collect2: ld returned 1 exit status
I have checked that curses.h anf ncurses.h exists in /usr/include directory and there is even man page for raw on my linux system.
Please tell me how to correct this error.
Pass "-lcurses" or "-lncurses" or something like that to the linker.
gcc foo.c -lcurses
works for me.
You need to link with curses or ncurses library:
gcc yourcode.c -lcurses -lncurses
Related
I was trying this on my 64 bit ubuntu:
First I've got a simple program
$ cat test.c
int f(int x){
int i=(x/42);
return i;
}
int main(){
return 0;
}
Then I manually specify how it's linked:
$ gcc test.c -nostdlib /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o /usr/lib/x86_64-linux-gnu/crtn.o
I got some errors:
/usr/lib/x86_64-linux-gnu/crt1.o：In function ‘_start’中：
(.text+0x12)：unresolved reference to ‘__libc_csu_fini’
/usr/lib/x86_64-linux-gnu/crt1.o：In function ‘_start’：
(.text+0x19)： unresolved reference to ‘__libc_csu_init’
/usr/lib/x86_64-linux-gnu/crt1.o：In function ‘_start’：
(.text+0x25)： unresolved reference to ‘__libc_start_main’
collect2: error: ld returned 1 exit status
I was trying to see how gcc deals with all necessary object files and try to do it manually. How to fix it? Thanks.
How to fix it?
You are missing libc symbols, so you need to link libc:
gcc test.c -nostdlib /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o /usr/lib/x86_64-linux-gnu/crtn.o -lc
Bear in mind that if you really want to link something "manually", you will do it with ld, not gcc
I am trying to get OpenSSL to work, but it seems to have a problem with linking. Here is what I did:
I downloaded OpenSSL for Linux from https://www.openssl.org/source/ I tried versions 0.9.8zc, 1.0.0o and 1.0.1j, all with the same result.
I installed each OpenSSL version using ./config, make and sudo make install.
For debugging purposes, I went to /usr/lib/ssl and used sudo chmod -R 777 * to remove any restrictions that could have caused the error.
I created the following program:
main.c:
#include <errno.h>
#include <malloc.h>
#include <resolv.h>
#include <openssl/bio.h>
#include <openssl/ssl.h>
int main(void) {
SSL_load_error_strings();
return EXIT_SUCCESS;
}
I created the following makefile in the same directory as my .c file:
makefile:
all: main.o
cc -o main main.o -L/usr/local/ssl/lib/ -lcrypto -lssl
main.o: main.c
cc -c -Wall main.c -I/usr/local/ssl/include/ -o main.o
When I run the makefile, I get the following error:
cc -o main main.o -L/usr/local/ssl/lib/ -lcrypto -lssl
/usr/local/ssl/lib//libssl.a(ssl_err2.o): In function SSL_load_error_strings':
ssl_err2.c:(.text+0x4): undefined reference toERR_load_crypto_strings'
/usr/local/ssl/lib//libssl.a(ssl_err.o): In function ERR_load_SSL_strings':
ssl_err.c:(.text+0xc): undefined reference toERR_func_error_string'
ssl_err.c:(.text+0x28): undefined reference to ERR_load_strings'
ssl_err.c:(.text+0x3c): undefined reference toERR_load_strings'
collect2: ld returned 1 exit status
make: *** [all] Error 1
What am I doing wrong?
Cheers
Alex
As answered on the maillist by scott_n but for the record here, swap the order to -lssl -lcrypto.
Explanation: for static C libraries in general on nearly all systems, members of library files like libxxx.a are only pulled in by the linker if they define things referenced from translation units already linked i.e. to the left in the command line. OpenSSL libssl has (numerous) references to libcrypto. If you link -lcrypto first, those references haven't been seen, so the libcrypto files aren't linked; then you link -lssl and create the unsatisfied references. In cases of mutual dependency also called recursive dependency you may need to repeat a library like -lcrypto -lssl -lcrypto but OpenSSL has no such "backward" references.
I successfully ran sudo apt-get install libncurses5-dev
Within my Eclipse window I then try to build the following HelloWord.cpp program:
#include <ncurses.h>
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}
I get the following error:
Invoking: GCC C++ Linker
g++ -m32 -lncurses -L/opt/lib -o "Test_V" ./src/curseTest.o ./src/trajectory.o ./src/xJus-epos.o -lEposCmd
/usr/bin/ld: cannot find -lncurses
collect2: error: ld returned 1 exit status
make: *** [Test_V] Error 1
It looks like the compiler is searching for the ncurses library and can't find it? I checked /usr/lib and the library does not exist there so do I need to manually link the ncurses library there - I thought the get-apt installer would automatically do this?
g++ HelloWorld.cpp -lncurses -o HelloWolrd
If you have a 32-bit machine, gcc compile m32 auto. If you have a 64-bit machine and you want to compile 32bits you
Your arguments are not in the correct order. You must specify all source files first and then linker search directories before specifying the libraries to link with. Your command should be like this:
g++ HelloWorld.o -L/opt/lib -lncurses -o HelloWorld
Taken from comment by #ChrisDodd:
Your options are in the wrong order -- -L must be BEFORE -l and both must be after all .o
My application uses my shared library. Application and library must be mudflapped to check out of bounds reads and writes both on stack and heap. Shared library was successfully build, but while linking application I had a lot of errors.
I made a simple example that reproduces this issue. Here are steps to reproduce:
create C++ dynamic shared library project with 2 files: h and cpp files with some class, and in h or cpp file use #include <iostream>
create C++ application that uses this library (uses class from inside shared library)
build library
build application (here you will catch an linking error)
Here are my files:
SharedLibTest.h
#ifndef SHAREDLIBTEST_H_
#define SHAREDLIBTEST_H_
#include <iostream>
class SharedLibTest {
public:
void func();
};
#endif /* SHAREDLIBTEST_H_ */
SharedLibTest.cpp
#include "SharedLibTest.h"
void SharedLibTest::func()
{}
main.cpp
#include <SharedLibTest.h>
int main(int argc, char *argv[])
{
SharedLibTest obj;
obj.func();
return 0;
}
Building the library:
g++ -O0 -g3 -Wall -c -fmessage-length=0 -fmudflap -funwind-tables -fPIC -MMD -MP -MF"SharedLibTest.d" -MT"SharedLibTest.d" -o "SharedLibTest.o" "../SharedLibTest.cpp"
g++ -rdynamic -shared -o "libshared_lib.so" ./SharedLibTest.o -lmudflap
Building the application:
g++ -I"/home/msviridov/work/prj/workspace/shared_lib" -O0 -g3 -Wall -c -fmessage-length=0 -fmudflap -funwind-tables -MMD -MP -MF"main.d" -MT"main.d" -o "main.o" "../main.cpp"
g++ -L"/home/msviridov/work/prj/workspace/shared_lib/Debug" -rdynamic -v -o "executable" ./main.o -lshared_lib -lmudflap
Linker error output is:
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<unsigned long>::__digits'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<long>::__min'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<short>::__min'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<char>::__max'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<short>::__max'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<long>::__max'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<int>::__max'
/home/msviridov/work/prj/workspace/shared_lib/Debug/libshared_lib.so: undefined reference to `__gnu_cxx::__numeric_traits_integer<int>::__min'
collect2: ld returned 1 exit status
make: *** [executable] Error 1
Though, if I remove mudflap compiler and linker flags for library the build of application will finish successfully.
But it's not true for vice versa.
I don't understand what does lead to such result.
My platform is Linux Mint 13 Maya 64 bit. I'll appreciate any help. Thanks.
Remove #include <iostream> from your header file. If you want to include iostream do that in your source (SharedLibTest.cpp) file.
Including it in header file also includes lots of garbage for you and also may cause some reference errors like this. Create SharedLibTest.o without that include and compare the sizes of object files.
You are probably hitting bug 53359 but you'd need recent 4.8 code to check. Furthermore, be advised that mudflap is for C and very simple C++ programs so you may find false possitives (ala bug 19319) and it doesn't work with DSOs yet.
I'm trying to compile a simple JNI application on an embedded Linux platform (a GuruPlug computer), but for some reason it's not linking to libc properly. The Java program I'm compiling is called Test.java:
public class Test {
static {
System.loadLibrary("Test");
}
public static void main(String[] args) {
new Test().printMessage();
}
public native void printMessage();
}
The implementation of printMessage() is in Test.c:
#include <jni.h>
#include <stdio.h>
#include "Test.h"
JNIEXPORT void JNICALL Java_Test_printMessage(JNIEnv *env, jobject obj)
{
printf("Message 123...\n");
}
I'm compiling Test.c with the following command on a bash shell:
gcc -g -shared -static -lc -Wl,-soname,libTest.so -I${JAVA_HOME}/include/ -I${JAVA_HOME}/include/linux/ Test.c -o libTest.so
When I run the above command, I get the error message "R_ARM_TLS_LE32 relocation not permitted in shared object". The full error message is:
/usr/bin/ld: /usr/lib/gcc/arm-linux-gnueabi/4.4.5/../../../libc.a(dl-tsd.o)(.text+0x18): R_ARM_TLS_LE32 relocation not permitted in shared object
Despite the error message, the JNI .so file is still written by the compiler, but running the Java application gives the following error message:
Exception in thread "main" java.lang.UnsatisfiedLinkError: /usr/lib/jni/libTest.so: /usr/lib/jni/libTest.so: unexpected reloc type 0x03
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1750)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1675)
at java.lang.Runtime.loadLibrary0(Runtime.java:840)
at java.lang.System.loadLibrary(System.java:1047)
at Test.<clinit>(Test.java:3)
Could not find the main class: Test. Program will exit.
Does anybody have any idea how to go about fixing this? Admittedly, the above code is a toy example, but I need to get a real JNI library compiling on this platform, and the real JNI library depends on libc. I can't seem to solve this basic issue of linking libc with a JNI library. Any suggestions would be greatly appreciated.
Thanks!
gcc -g -shared -static -lc -Wl,-soname,libTest.so -I${JAVA_HOME}/include/ -I${JAVA_HOME}/include/linux/ Test.c -o libTest.so
There are several problems with the command line above:
the -shared and -static flags are mutually exclusive, and the second overrides the first
when linking shared libraries, you want -fPIC on most architectures
the -lc is in the wrong place (should follow your sources, not precede them), and is not necessary anyway: gcc will add it automatically
you don't strictly need the -soname either; it's just useless clutter
The correct command then is:
gcc -g -shared -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux \
Test.c -o libTest.so