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GCC lpthread compilation woes [message #1817309]

Wed, 20 November 2019 10:15

Huyen John

Messages: 1
Registered: November 2019

Junior Member

Let me preface this by saying I'm doing this for a class. Generally I live in SQL, this is one of my first forays into Linux and C. A header and code file were provided with the text book, they require the lpthread flag to be set during compilation and linking. Below are the commands eclipse issues to build the project. When I compile with eclipse, here's the error I'm running into.

**** Build of configuration Debug for project HW2 ****

make all
Building file: ../src/csapp.c
Invoking: GCC C Compiler
gcc -O0 -g3 -Wall -c -fmessage-length=0 -lpthread -MMD -MP -MF"src/csapp.d" -MT"src/csapp.d" -o "src/csapp.o" "../src/csapp.c"
Finished building: ../src/csapp.c

Building file: ../src/problem10.6.c
Invoking: GCC C Compiler
gcc -O0 -g3 -Wall -c -fmessage-length=0 -lpthread -MMD -MP -MF"src/problem10.6.d" -MT"src/problem10.6.d" -o "src/problem10.6.o" "../src/problem10.6.c"
Finished building: ../src/problem10.6.c

Building target: HW2
Invoking: GCC C Linker
gcc -lpthread -o "HW2" ./src/csapp.o ./src/problem10.6.o
./src/csapp.o: In function `Pthread_create':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:461: undefined reference to `pthread_create'
./src/csapp.o: In function `Pthread_cancel':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:468: undefined reference to `pthread_cancel'
./src/csapp.o: In function `Pthread_join':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:475: undefined reference to `pthread_join'
./src/csapp.o: In function `Pthread_detach':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:483: undefined reference to `pthread_detach'
./src/csapp.o: In function `Pthread_once':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:497: undefined reference to `pthread_once'
./src/csapp.o: In function `Sem_init':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:506: undefined reference to `sem_init'
./src/csapp.o: In function `P':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:512: undefined reference to `sem_wait'
./src/csapp.o: In function `V':
/home/sonek/Documents/Workspace/HW2/Debug/../src/csapp.c:518: undefined reference to `sem_post'
collect2: ld returned 1 exit status
make: *** [HW2] Error 1

**** Build Finished ****

When I copied the scr directory to the desktop and compiled directly through GCC and terminal, it worked. Here are the slightly modified commands I executed.

gcc -O0 -g3 -Wall -c -fmessage-length=0 -lpthread -MMD -MP -MF"csapp.d" -MT"csapp.d" -o "csapp.o" "csapp.c"
gcc -O0 -g3 -Wall -c -fmessage-length=0 -lpthread -MMD -MP -MF"problem.d" -MT"problem.d" -o "problem.o" "problem.c"
gcc -lpthread -o "HW2" csapp.o problem.o

So it seems I have the library installed but eclipse is having trouble finding it. Anyone know what I'm doing wrong?

I'm building this on a freshly build Ubuntu VM

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