Pthread_create hangs program

Altera_Forum · ‎10-12-2010

Hi,

I'm trying to compile some C++ code that uses pthread on uClinux.

I'm using this toolchain:

http://www.nioswiki.com/index.php?title=OperatingSystems/UClinux/BinaryToolchain

I can compile C++ code just fine, but whenever I try to use pthreads, the program will hang at the pthread_create () call.

At this point I'm just trying to compile a very simple program. It will hange right at the create call and never exit.

In addition, I get a linker error when trying to use pthread_join.


# include <iostream># include <pthread.h># include <unistd.h>
void *ReadMessagesThread(void *ptr);
int main(int argc, char** argv)
{
   using namespace std;
   pthread_t thread;
   cout << "starting pthread..." << endl;
   int rc = pthread_create(&thread, NULL, ReadMessagesThread, NULL);
   cout << "return value is : " << rc << endl;
   //pthread_join(thread, NULL);
   return 0;
}
void *ReadMessagesThread(void *ptr)
{
   using namespace std;
   for (int i = 0; i < 5; i++)
   {
      cout << "In thread : " << i << endl;
   }
}

Here is the MakeFile I'm using:


PROJ_NAME = remoteModelServer
CXX=nios2-linux-uclibc-g++
LDLIBS:=-lpthread $(LDLIBS)
CFLAGS=-O2 -fno-gnu-keywords
LDFLAGS=-Wl,-elf2flt 
$(PROJ_NAME): *.cpp
    $(CXX) $(LDLIBS) $(CFLAGS) $(LDFLAGS) -o $(PROJ_NAME).exe *.cpp 
.PHONY: clean
clean:
    -rm -f *. *.elf *.gdb *.bin *.exe *.flt

Any ideas what I could be doing wrong?

Thanks

Altera_Forum · ‎10-19-2010

So I did a nios2-elf-objdump on the gdb file created and there is this line:

00000000 w *UND* 00000000 pthread_create

Which seems to imply that my program isn't properly finding the pthread library.

I tried to specify the path to libpthread.a by using the -L option in the MakeFile, but that did not work.

Any other ideas what could be wrong?

Altera_Forum · ‎05-04-2011

Hey Kag,

I'm experiencing the same problem. Have you found a way to fix it?

There seems to be with the linking process, I removed the -lpthread from the linker arguments and it doesn't complain about it.

Is there a way to check this? Why does the GPP automatically links the phtread lib? And why does the GCC not.

Would be great if you or someone else could help me.

Thanks

Altera_Forum · ‎05-04-2011

I made some progress with the Problem, linking of the pthead-lib is not correctly done by G++. I managed to improve the situation describe by Hag by adding the path to the pthread.a to the linker command.

It looks like this:


nios2-linux-c++ -o ijpis -elf2flt="-s 65536" include/tinyxml.o include/tinyxmlparser.o include/tinyxmlerror.o include/tinystr.o opt/nios2/lib/libpthread.a

After that, it is able to link the invocation of pthread_join() and the objectdumb shows:


0001b170 g     F .text	0000010c pthread_create

The situation is improved, but after starting the program it still hangs after pthread_create...

A note at the end: I use the gcc version 3.4.6. I haven't tried to use another, yet.

Best regards