pthread 和 semaphore 在 osx maverick 10.9 中不适用于我

我有以下涉及 pthread 和信号量的简单程序。我使用的是 os x Maverick 10.9。我使用 makefile 来编译程序（而不是 xcode）。我使用c++11。

#include <pthread.h>
#include <semaphore.h>
#include <cassert>
#include <iostream>

#define ASSERT(a) if(!(a)) abort

using namespace std;

sem_t countMutex;
int myCount=0;

void *doThread(void *data) {
    int *pi = reinterpret_cast<int *>(data);
    sem_wait(&countMutex);
    for(int i =0 ;i < 100; ++i) {
        myCount += 1;
    }
    sem_post(&countMutex);
    pthread_exit( NULL );
}

void LaunchThread() {
    const int kNumThreads = 10;
    pthread_t tids[kNumThreads];
    int threadData[kNumThreads];
    pthread_attr_t attr;
    pthread_t tid;
    int retVal=0;
    retVal = pthread_attr_init(&attr);
    ASSERT(retVal == 0);
    retVal = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE );
    ASSERT(retVal == 0);
    sem_init(&countMutex, 0, 1);
    myCount = 0;
    for(int i=0; i < kNumThreads; ++i) {
        threadData[i] = i;
        retVal = pthread_create( &tids[i], &attr, &doThread, &threadData[i]);
        if(retVal != 0) {
            cerr << "cannot create thread" << endl;
            return;
        }
    }

    retVal = pthread_attr_destroy(&attr);
    ASSERT(retVal == 0);
    void *status = NULL;
    for(int i=0; i < kNumThreads; ++i) {
        retVal = pthread_join( tids[i], &status);
        if(retVal != 0) {
            cerr << "cannot join ghread " << i << ", " << tids[i] << endl;
            return;
        }
        cout << "completed thread " << i << ", " << tids[i] << endl;
    }
    cout << "value of myCount: " <<  myCount << endl;
    sem_destroy(&countMutex);
    //sem_unlink(&countMutex);
    pthread_exit( NULL );
}
int main( int argc, char **argv) {
    LaunchThread();
    return 0;
}

编译这个的makefile是

CXX=clang++
CXXFLAGS=-g -Wall -Wno-deprecated -std=c++11 -pthread  -D DEBUG -g3 $(INCLUDES)
LDFLAGS=$(LIBS)

OBJS=main.o
PROG=test

all: $(PROG)


$(PROG): $(OBJS)
$(CXX) -v -o $(PROG) main.o $(LDFLAGS)

%.o: %.cpp
$(CXX) -c $(CXXFLAGS) $<

clean:
rm $(OBJS); rm test

该程序应该报告 1000 的值myCount。但在多次运行中不一致。

Eg:

completed thread 0, 0x107dca000
completed thread 1, 0x107e4d000
completed thread 2, 0x107ed0000
completed thread 3, 0x107f53000
completed thread 4, 0x107fd6000
completed thread 5, 0x108059000
completed thread 6, 0x1080dc000
completed thread 7, 0x10815f000
completed thread 8, 0x1081e2000
completed thread 9, 0x108265000
value of myCount: 900

OSX 不支持未命名的 POSIX 信号量。如果您检查返回代码，您会看到sem_init失败并出现错误。您需要使用命名信号量。

Use sem_open代替sem_init。不要使用sem_destroy而是 sem_close 和sem_unlink.

你会很高兴去的。