Undefined reference to pthread_create

Question

I have this code:

#include <stdio.h>
#include <pthread.h>

void* cuoco(void* arg)
{
    fprintf(stderr,"Inizio codice cuoco\n");
    fprintf(stderr,"Fine codice cuoco\n");
    return NULL;
}

void* cameriere(void* arg)
{
    fprintf(stderr,"Inizio codice cameriere\n");
    fprintf(stderr,"Fine codice cameriere\n");
    return NULL;
}

void* cliente(void* arg)
{
    fprintf(stderr,"Inizio codice cliente\n");
    fprintf(stderr,"Fine codice cliente\n");
    return NULL;
}

int main(int argc, char* argv[])
{
    void* (*routine)(void*);
    routine=cuoco;
    pthread_t thread_cuoco,thread_cameriere,thread_cliente;
    pthread_create(&thread_cuoco,NULL,routine,NULL);
    return 0;
}

And in the compiler options I insert -lpthread
But it says:
"Undefined reference to pthread_create"
I use ubuntu 10.10, so I already have pthread library installed, I can't figure the reason of this error.

How did you add the linker option & where? Which version of Code::Blocks? — another.anon.coward, Mar 21 '12 at 11:20
Possible duplicate of [Undefined reference to pthread\_create in Linux](https://stackoverflow.com/questions/1662909/undefined-reference-to-pthread-create-in-linux) — 1201ProgramAlarm, Apr 15 '19 at 23:45

score 30 · Accepted Answer · edited Nov 29 '15 at 12:50

30

Use -lpthread as the last compiler flag.

example: gcc -o sample sample.c -lpthread

edited Nov 29 '15 at 12:50

stdcall

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answered Mar 21 '12 at 11:00

1

@RamyAlZuhouri No you don't. You probably botched the codeblocks settings. +1 to counter wrong downvote. – cnicutar Mar 21 '12 at 11:05
Yes, I have put it.It's on settings->compiler and debugger->(compiler settings tab)->other options. – Ramy Al Zuhouri Mar 21 '12 at 11:21
3

@RamyAlZuhouri: That is not right. It is more of a linker setting. So do this: settings->compiler and debugger->linker settings (tab). Select "Add" under Link libraries section. Add the path to pthread library (most likely /usr/lib/libpthread.so). Try building then – another.anon.coward Mar 21 '12 at 11:31
Plus you should not downvote if you tried it, but it didn't work, but you didn't tell it us either... – May 16 '12 at 12:42
2

Note that the use of `-pthread` is preferable, because `-lpthread` will fail to link on a system with only `libpthread.a` installed. – e-sushi Apr 22 '15 at 20:37

hmjd · Answer 2 · 2012-03-21T11:08:53.087

15

Without seeing the compiler command, I suspect -lpthread is not at end. Libraries need to be placed at end of the compiler command:

gcc main.c -lpthread

However, use -pthread instead of -lpthread, as -pthread may add other settings (like defining the macro _REENTRANT for example).

edited Mar 21 '12 at 11:08

answered Mar 21 '12 at 11:00

hmjd

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I compile it with code::blocks, in the C::B options now I changed _-lpthread_ with _-pthread_, but nothing has changed. This is the only options I have in settings. – Ramy Al Zuhouri Mar 21 '12 at 11:02
I am unfamiliar with code::blocks, but can you attempt a complete rebuild of the source? – hmjd Mar 21 '12 at 11:03

score 5 · Answer 3 · edited Apr 09 '19 at 14:26

5

Use the following command:

gcc -pthread -o main main.c

edited Apr 09 '19 at 14:26

Jared Forth

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answered Nov 20 '12 at 17:12

AbdulFattah Popoola

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score 0 · Answer 4 · edited Apr 09 '19 at 15:26

0

In Eclipse, you should add string pthread.

Project -> Properties -> C/C++ Build -> Settings -> Tool Settings -> GCC Linker -> Libraries -> Libraries (-l) -> Add -> pthread

After this, you can Build your project.

edited Apr 09 '19 at 15:26

Jared Forth

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answered May 15 '16 at 12:35

ognjenkl

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1

But the OP said in a comment that he is using Code::Blocks, not Eclipse. – Fabio says Reinstate Monica May 15 '16 at 13:08

score -2 · Answer 5 · edited Apr 09 '19 at 14:49

-2

found the solution guys :D just go to settings >> compiler >> linker tab >>add lib

go to drive and go to lib folder and find x86_64_linux_gnu and find pthread enjoy :)

edited Apr 09 '19 at 14:49

Jared Forth

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answered Jun 02 '15 at 14:44

AFsoft

1

Undefined reference to pthread_create

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