Undefined reference to pthread create in Linux

Question

I picked up the following demo off the web from https   computing llnl gov tutorials pthreads    include  lt pthread h gt   include  lt stdio h gt   define NUM THREADS     5  void  PrintHello void  threadid       long tid     tid    long threadid     printf  Hello World  It s me  thread   ld  n   tid      pthread exit NULL      int main  int argc  char  argv         pthread t threads NUM THREADS      int rc     long t     for t 0  t lt NUM THREADS  t           printf  In main  creating thread  ld n   t         rc   pthread create  amp threads t   NULL  PrintHello   void   t         if  rc            printf  ERROR  return code from pthread create   is  d n   rc            exit -1                   pthread exit NULL       But when I compile it on my machine  running Ubuntu Linux 9 04  I get the following error   corey ubuntu   demo  gcc -o term term c term c  In function    main     term c 23  warning  incompatible implicit declaration of built-in function    exit     tmp cc8BMzwx o  In function  main   term c   text 0x82   undefined reference to  pthread create  collect2  ld returned 1 exit status   This doesn t make any sense to me  because the header includes pthread h  which should have the pthread create function  Any ideas what s going wrong

User · Answer

If you are using cmake  you can use   add compile options -pthread    Or   SET CMAKE CXX FLAGS    CMAKE CXX FLAGS  -pthread

User · Answer

check man page and you will get   Compile and link with -pthread   SYNOPSIS         include  lt pthread h gt          int pthread create pthread t  thread  const pthread attr t  attr                            void    start routine   void     void  arg            Compile and link with -pthread

User · Answer

You need to use the option -lpthread with gcc

User · Answer

in eclipse   properties- c c  Build- setting- GCC C   linker- libraries in top part add  pthread

User · Answer

Compile it like this   gcc demo c -o demo -pthread

User · Answer

Sometimes  if you use multiple library  check the library dependency   e g  -lpthread -lSDL     lt         -lSDL -lpthread

User · Answer

For Linux the correct command is   gcc -o term term c -lpthread    you have to put -lpthread just after the compile command this command will tell to the compiler to execute program with pthread h library  gcc -l links with a library file Link -l with library name without the lib prefix

User · Answer

Both answers to this question so far are incorrect  For Linux the correct command is   gcc -pthread -o term term c   In general  libraries should follow sources and objects on command line  and -lpthread is not an  option   it s a library specification  On a system with only libpthread a installed    gcc -lpthread       will fail to link

User · Answer

you need only Add  pthread   in  proprieties  C C   build  GCC C   Linker  Libraries   top part  Libraries -l    thats it

User · Answer

Running from the Linux terminal  what worked for me was compiling using the following command  suppose the c file I want to compile is called test c    gcc -o test test c -pthread   Hope it helps somebody

User · Answer

In Anjuta  go to the Build menu  then Configure Project   In the Configure Options box  add   LDFLAGS  -lpthread    Hope it ll help somebody too

User · Answer

I believe the proper way of adding pthread in CMake is with the following  find package  Threads REQUIRED   target link libraries helloworld       CMAKE THREAD LIBS INIT

User · Answer

Acutally  it gives several examples of compile commands used for pthreads codes are listed in the table below  if you continue reading the following tutorial   https   computing llnl gov tutorials pthreads  Compiling

User · Answer

In Visual Studio 2019 specify -pthread in the property pages for the project under      Linker -  Command Line -  Additional Options   Type in -pthread in the textbox

User · Answer

Since none of the answers exactly covered my need  using MSVS Code   I add here my experience with this IDE and CMAKE build tools too  Step 1  Make sure in your  cpp   or  hpp if needed  you have included   include  lt functional gt   Step 2 For MSVSCode IDE users  Add this line to your c cpp properties json file   quot compilerArgs quot     quot -pthread quot      Step 2 For CMAKE build tools users  Add this line to your CMakeLists txt set CMAKE CXX FLAGS  quot -pthread quot    Note  Adding flag -lpthread  instead of -pthread  results in failed linking

[c] Undefined reference to pthread_create in Linux

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