#include <stdio.h>
#include <pcap.h>
int main(int argc,char* argv[])
{
char* dev=argv[1];
char errbuf[PCAP_ERRBUF_SIZE];
dev=pcap_lookupdev(errbuf);
if(dev==NULL) {
fprintf(stderr,"Couldn't find default device: %s\n",errbuf);
return 0;
}
printf("Device: %s\n",dev);
return 0;
}
On compiling:
$ cc pcap1.c
/tmp/ccZLrRlF.o: In function `main':
pcap1.c:(.text+0x37): undefined reference to `pcap_lookupdev'
collect2: ld returned 1 exit status
This is happening with other functions of the libpcap library as well. Can you please explain the problem to me and a way to correct it? Thanks in advance...
Because you're not linking the pcap library when you're compiling, therefore none of the functions you're trying to use are available.
cc pcap1.c -lpcap
If you haven't installed libpcap somewhere in the standard library path, you would need to add that as well
cc pcap1.c -lpcap -L/directory/libpcap/is/in
I had this Error and I have just solved it.
I am working on Debian 7 so here is what I have done:
1 - insaled the libpcap you find how in this link install libpcap
!!!!!! installed flex (sudo apt-get install bison) because I had some problems while
installing libpcap
2 - gcc test.c -lpcap that returned this error " collect2: ld returned 1 exit status "
3 - installed libpcap-devel (sudo apt-get install libpcap-dev)
and it went through the next time
I hope this is going to be of help to you.
good luck
Related
I'd like to build on this post, because my symptoms are identical, but the solution seems to be something else.
I am working in a Ubuntu container (Ubuntu 16.04.3 LTS), trying to compile a toy C program that will eventually connect to an SQL server. First things first: I have the latest libmysqlclient-dev installed:
root#1234:/home# apt install libmysqlclient-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
libmysqlclient-dev is already the newest version (5.7.24-0ubuntu0.16.04.1).
0 upgraded, 0 newly installed, 0 to remove and 88 not upgraded.
root#1234:/home#
And when I look in the /usr/include/mysql directory, I see the critical header file I'll need:
root#1234:/home# ls -l /usr/include/mysql | grep mysql.h
-rw-r--r-- 1 root root 29207 Oct 4 05:48 /usr/include/mysql/mysql.h
root#1234:/home#
So far, so good. Now I found this little toy program from here:
#include <stdio.h>
#include "/usr/include/mysql/mysql.h"
int main() {
MYSQL mysql;
if(mysql_init(&mysql)==NULL) {
printf("\nInitialization error\n");
return 0;
}
mysql_real_connect(&mysql,"localhost","user","pass","dbname",0,NULL,0);
printf("Client version: %s",mysql_get_client_info());
printf("\nServer version: %s",mysql_get_server_info(&mysql));
mysql_close(&mysql);
return 1;
}
Now, following the advice of the previous post, I compile using the "-I" option to point to the mysql.h header file. (Yes, I am required to use GCC here):
root#1234:/home# gcc -I/usr/include/mysql sqlToy.c
/tmp/cc8c5JmT.o: In function `main':
sqlToy.c:(.text+0x25): undefined reference to `mysql_init'
sqlToy.c:(.text+0x69): undefined reference to `mysql_real_connect'
sqlToy.c:(.text+0x72): undefined reference to `mysql_get_client_info'
sqlToy.c:(.text+0x93): undefined reference to `mysql_get_server_info'
sqlToy.c:(.text+0xb4): undefined reference to `mysql_close'
collect2: error: ld returned 1 exit status
root#1234:/home#
Belly flop! The compiler has no idea what all the mySQL functions are, even though I've done all I can think of to point to that header file. As a sanity check, I made sure those mySQL functions are indeed in that header file; here's one as an example:
root#1234:/home# more /usr/include/mysql/mysql.h | grep mysql_init
libmysqlclient (exactly, mysql_server_init() is called by mysql_init() so
MYSQL * STDCALL mysql_init(MYSQL *mysql);
root#1234:/home#
So while I've pointed the compiler to the mysql.h header file in both my code AND with the "-I" option, it still has no clue what those 'mysql' functions are. The "-I" option was the solution in the previous post, but is not working for me here.
So... What might be the problem? I'm assuming this isn't a compiling problem, but maybe a linking one? In other words, I'm showing GCC where the mysql.h file is, but he is still not using it when processing the code?
Headers are not libraries. You are including the MySQL header during compilation, so these functions are defined, but you are not linking against the library which actually provides those functions.
These functions are provided by the libmysqlclient library, so you need to add the -lmysqlclient flag to your command line to fix this. (Note that this is a lower-case l, not an I.)
Additionally, since you are adding /usr/include/mysql to your system header path, you can include the library as
#include <mysql.h>
You do not need to -- and should not! -- specify the full path to the library in the #include directive.
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 5 years ago.
I'm trying to get started with using mySQL C API for a project that I'm hoping to complete.
I've downloaded the mySQL Community Server version and the mySQL Connector/C from the official site.
Q1: Do I also need to download Connector/ODBC? What is the difference?
So, this is a basic program that I learnt and am trying to compile and link:
#include<stdio.h>
#include<mysql.h>
int main(int argc, char **argv)
{
printf("MySQL client version: %s\n", mysql_get_client_info());
exit(0);
}
I'm extremely confused as to what commands for compilation and linking I should use. When I do the following, this happens:
gcc mySQL.c -I/usr/local/mysql/include
Undefined symbols for architecture x86_64:
"_mysql_get_client_info", referenced from:
_main in mySQL-a3f748.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Can someone just help me out with this? I've struggled a lot and it all seems extremely confusing.
My question is about compiling and linking mySQL C API libraries and not the error.
The header file <mysql.h> only declares the functions and types needed. The actual function definition (its implementation) is in a library you need to link with.
You do that with the -l (lower-case L) option:
gcc mySQL.c -I/usr/local/mysql/include -lmysql
However, since you seem to have installed MySQL in a non-standard location, you might have to use the -L option to specify where the library is located (similar to the -I option):
gcc mySQL.c -I/usr/local/mysql/include -L/usr/local/mysql/lib -lmysql
This should at least make your program build. But there is still another issue that might come up if your MySQL library is not a static library but a dynamic library (i.e. a "DLL"), because the run-time loader will not know the location of the dynamic library. You need a special linker-flag for that too:
gcc mySQL.c -I/usr/local/mysql/include -L/usr/local/mysql/lib -lmysql -Wl,-rpath=usr/local/mysql/lib
i'm writing a simple code for fast fourier transform with cufft cuda library. My source file work well with visual studio in windows7 but with eclipse nsight, in ubuntu 14.04, not work!
i've installed nvidia 346.72 driver and cuda toolkit 7.0 and my video hardware is geforce 410M. When i build my source code i have following message:
16:56:24 **** Incremental Build of configuration Debug for project cufft_double ****
make all
Building target: cufft_double
Invoking: NVCC Linker
/usr/local/cuda-7.0/bin/nvcc --cudart static -L/usr/local/cuda-7.0/lib64 --relocatable-device-code=false -gencode arch=compute_20,code=compute_20 -gencode arch=compute_20,code=sm_20 -m64 -link -o "cufft_double" ./cufft_double.o
./cufft_double.o: In function `main':
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:79: undefined reference to `cufftPlan1d'
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:85: undefined reference to `cufftExecZ2Z'
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:108: undefined reference to `cufftDestroy'
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:111: undefined reference to `cufftPlan1d'
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:117: undefined reference to `cufftExecZ2Z'
/home/marco/cuda-workspace/cufft_double/Debug/../cufft_double.cu:136: undefined reference to `cufftDestroy'
collect2: error: ld returned 1 exit status
make: *** [cufft_double] Error 1
16:56:27 Build Finished (took 2s.792ms)
i tried to set library path but in preferences windows i read "no CUDA-compatible devices detected"
please help me!
Best reguards
marco
now i can build source code but my program not work!
i read this error:
modprobe: ERROR: could not insert 'nvidia_331_uvm': Invalid argument
and i receive a message programmed by me if "cudaGetLastError() != cudaSuccess"
after "cudaMalloc"
For best clarification i read "cuda error: allocazione fallita" for this frame of code:
cudaMalloc((void**)&out_device, sizeof(cufftDoubleComplex)*NX*BATCH);
if (cudaGetLastError() != cudaSuccess){
printf("Cuda error: allocazione fallita\n");
return 0;
};
Run these commands in sequence:
sudo apt-get remove --purge nvidia-*
sudo apt-get install cuda-drivers
sudo apt-get install nvidia-nsight
Restart the machine and open nsight and look at the properties whether you see the detected driver.
I wrote a simple program for eCos in stm32f4discovery Cortex-M4, which following steps below.
$ecosconfig new stm32f4discovery
$configtool
#include <stdio.h>
int main(){
printf("hello ecos!\r\n");
return 0;
}
$arm-none-eabi-gcc -o hello.elf hello.c -Lecos_install/lib -I ecos_install/include -mcpu=cortex-m4 -mthumb -g -O2 -ffunction-sections -fdata-sections -Ttarget.ld -nostdlib
$arm-none-eabi-objcopy -O binary -R .sram hello.elf hello.bin
Actually, it is success. But, I don't know how to see the "hello ecos!".
I guess I need to setup baud rate and tty. So, I use minicom to do this. Unfortunately, I failed.
I use this stlink util to debug STM32F4 apps. After you compile and invoke this util, you can connect to stm32 target with gdb:
(gdb) tar ext :4242
(gdb) load hello.elf
Then you should be able to debug your app.
On OpenSuse 11.2, I successfully compiled, linked, and ran the following code which installs a data source for a MySQL database with unixODBC:
#include <iostream>
#include <sql.h>
#include <sqlext.h>
#include <odbcinst.h>
/* Add a data source for the following MySQL db: db=testdb, username=test, password = test. */
void inst()
{
BOOL ret = SQLConfigDataSource(NULL, ODBC_ADD_DSN, "MySQL driver",
"DSN=mysource\0UID=test\0PWD=test\0DATABASE=testdb\0\0");
if (!ret) {
DWORD errCode;
char errBuf[SQL_MAX_MESSAGE_LENGTH];
WORD msgLen;
SQLInstallerError(1, &errCode, errBuf, SQL_MAX_MESSAGE_LENGTH, &msgLen);
std::cerr << errBuf << std::endl;
}
}
int main()
{
inst();
return 0;
}
With the same code on Debian Lenny, I have had problems. First, I compiled this code the following way:
c++ -o main main.cc -lodbc -lodbcinst -L/usr/lib/odbc -lmyodbc
It went ok. But when I attempted to run the resulting binary, I got a linker error which in fact was confirmed by typing ldd main:
libmyodbc3_r-3.51.15.so => not found
Although I correctly installed unixODBC and the associated MySQL driver (myodbc) on my host (Debian Lenny) the simplest way (i.e. via aptitude), I could not find this shared library.
I wrongly thought, well, I will create a symlink on /usr/lib/odbc/libmyodbc.so. Anyway now my program returns the following message:
General installer error
So I feel the file libmyodbc3_r-3.51.15.so is really missing.
Note: on Debian Lenny, the version of unixODBC is 2.2.11, and the version of MySQL is 5.0.51a
Anyone ever ran into such a situation ? Any help would be appreciated.
The option
-L/usr/lib/odbc
tells the compiler where to find the library for linking.
But the system doesn't know where to find the library when you run the executable.
You need to either statically link against libmyodbc, or tell the system where to find the library.
The first can be done by changing
-lmyodbc
to
-static -lmyodbc
The second can be done by editing /etc/ld.so.conf (or adding to /etc/ld.so.conf.d) and re-running ldconfig or by setting the LD_LIBRARY_PATH environment variable to include /usr/lib/odbc