Dear all,
I've got the following problem: I want to use the boost threading library provided in version 1.36 on an arm (imx31) based evaluation board with MontaVista linux and g++ version 4.2.0 on it.
When I try to compile the following example with my arm-g++ compiler
#include <vector>
#include
#include
#include
class Worker
{
private:
int _id; ///< The id of the worker.
public:
Worker( int id ) : _id( id ) {}
// Is the function that is called when this worker is started.
// Doesn't do anything usefull.
void run()
{
for (unsigned int i=0; i<30000000; i++);
}
};
typedef boost::shared_ptr<Worker> worker_ptr;
typedef std::vector worker_vec;
// Starts worker threads.
void run( int nr_workers )
{
worker_vec workers( nr_workers );
boost::thread_group tg;
for (int i = 0; i < nr_workers; i++) {
worker_ptr w( new Worker(i) );
workers[i] = w;
tg.create_thread( boost::bind( &Worker::run, w ) );
}
tg.join_all();
}
int main( int argc, char *argv[] )
{
int worker_nr = 5;
run( worker_nr );
return 0;
}
I get the following error message:
/opt/montavista/mobilinux/devkit/arm/v6_vfp_le/lib/gcc/armv6fl-montavista-linux-gnueabi/4.2.0/../../../../armv6fl-montavista-linux-gnueabi/bin/ld: thread-test: hidden symbol `__sync_add_and_fetch_4' in /opt/montavista/mobilinux/devkit/arm/v6_vfp_le/lib/gcc/armv6fl-montavista-linux-gnueabi/4.2.0/libgcc.a(linux-atomic.o) is referenced by DSO
/opt/montavista/mobilinux/devkit/arm/v6_vfp_le/lib/gcc/armv6fl-montavista-linux-gnueabi/4.2.0/../../../../armv6fl-montavista-linux-gnueabi/bin/ld: final link failed: Nonrepresentable section on output
collect2: ld returned 1 exit status
I do not get any linking errors while compiling it on my PC, so may be there is missing something?
I've read in "http://lists.boost.org/Archives/boost/2007/09/127103.php " that this problems comes from the fact that
__sync__fetch_and_add(&x,1) , which is needed by shared_pointers, is not implemented in gcc for ARM.
So according to the problem stated above I've two questions:
- Does there already exist a workaround which solves the problem mentioned above?
- I have added a new header file (atomic_count_arm.hpp) to the boost/detail directory. It implements the atomic_count
class with specific arm inline assemply instructions in the operator overloads functions.
#ifndef BOOST_DETAIL_ATOMIC_COUNT_ARM_HPP_INCLUDED
#define BOOST_DETAIL_ATOMIC_COUNT_ARM_HPP_INCLUDED
namespace boost
{
namespace detail
{
class atomic_count
{
public:
explicit atomic_count( long v ) : value_( v ) {}
void operator++()
{
long tmp;
int result;
__asm__ __volatile__(
"1: ldrex %0, [%2]\n"
" add %0, %0, #1\n"
" strex %1, %0, [%2]\n"
" cmp %1, #0\n"
" bne 1b"
: "=&r"(tmp), "=&r"(result) // output parameters
: "r"(&value_) // input parameters
: "memory", "cc" // clobbers
);
}
long operator--()
{
long tmp;
int result;
__asm__ __volatile__(
"1: ldrex %0, [%2]\n"
" add %0, %0, #-1\n"
" strex %1, %0, [%2]\n"
" cmp %1, #0\n"
" bne 1b"
: "=&r"(tmp), "=&r"(result) // output parameters
: "r"(&value_) // input parameters
: "memory", "cc" // clobbers
);
}
operator long() const
{
long tmp;
int result;
__asm__ __volatile__(
"1: ldrex %0, [%2]\n"
" strex %1, %0, [%2]\n"
" cmp %1, #0\n"
" bne 1b"
: "=&r"(tmp), "=&r"(result) // output parameters
: "r"(&value_) // input parameters
: "cc" // clobbers
);
return tmp;
}
private:
atomic_count(atomic_count const &);
atomic_count & operator=(atomic_count const &);
mutable long value_;
};
} // namespace detail
} // namespace boost
#endif
Further I've added the following lines into atomic_count.hpp:
#elif defined( __GNUC__ ) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 ) && defined( __arm__ )
#include
and before:
#elif defined( __GNUC__ ) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 )
# include
Then I recompiled boost and the threading example given above and suprise, it compiles. I'm also able to
execute the test-program.
So, do you think that this is feasable solution?
Best regards,
Rudi Dittrich
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Matthew L. Creech
Rudi Dittrich